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  • Can anyone help me find why this C program work on VS2005 but not on DEV-C++

    - by user333771
    Hello to everybody..and greetings from Greece I have a C program for an exercise and it has a strange issue The program runs just fine on VS 2005 but it crashes on DEV-C++ and the problem that the problem is that the exercise is always evaluated against DEV-C++ The program is about inserting nodes to a BST and this is where the problem lies... Well i would really appreciate some help. enter code here #include <stdio.h> #include <stdlib.h> #include <malloc.h> typedef struct tree_node { int value; int weight; struct tree_node *left; struct tree_node *right; } TREE_NODE; /* The Following function creates a Binary Search Treed */ TREE_NODE *create_tree(int list[], int size); TREE_NODE *search_pos_to_insert(TREE_NODE *root, int value, int *left_or_right); /* this is the problematic function */ void inorder(TREE_NODE *root); /* Inorder Traversing */ TREE_NODE *temp; int main() { TREE_NODE *root; /* Pointer to the root of the BST */ int values[] = {10, 5, 3, 4, 1, 9, 6, 7, 8, 2}; /* Values for BST */ int size = 10, tree_weight; root = create_tree(values, 10); printf("\n"); inorder(root); /* Inorder BST*/ system("PAUSE"); } TREE_NODE *search_pos_to_insert(TREE_NODE *root, int value, int *left_or_right) { if(root !=NULL) { temp = root; if(value >root->value) { *left_or_right=1; *search_pos_to_insert(root->right, value, left_or_right); } else { *left_or_right=0; *search_pos_to_insert(root->left, value, left_or_right); } } else return temp;/* THIS IS THE PROBLEM (1) */ } TREE_NODE *create_tree(int list[], int size) { TREE_NODE *new_node_pntr, *insert_point, *root = NULL; int i, left_or_right; /* First Value of the Array is the root of the BST */ new_node_pntr = (TREE_NODE *) malloc(sizeof(TREE_NODE)); new_node_pntr->value = list[0]; /* ¸íèåóå ôçí ðñþôç ôéìÞ ôïõ ðßíáêá. */ new_node_pntr->weight = 0; new_node_pntr->left = NULL; new_node_pntr->right = NULL; root = new_node_pntr; /* Now the rest of the arrat. */ for (i = 1; i < size; i++) { insert_point = search_pos_to_insert(root, list[i], &left_or_right); /* THIS IS THE PROBLEM (2) */ /* insert_point just won't get the return from temp */ new_node_pntr = (TREE_NODE *) malloc(sizeof(TREE_NODE)); new_node_pntr->value = list[i]; new_node_pntr->weight = 0; new_node_pntr->left = NULL; new_node_pntr->right = NULL; if (left_or_right == 0) insert_point->left = new_node_pntr; else insert_point->right = new_node_pntr; } return(root); } void inorder(TREE_NODE *root) { if (root == NULL) return; inorder(root->left); printf("Value: %d, Weight: %d.\n", root->value, root->weight); inorder(root->right); }

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  • Mallocing an unsigned char array to store ints

    - by Max Desmond
    I keep getting a segmentation fault when i test the following code. I am currently unable to find an answer after having searched the web. a = (byte *)malloc(sizeof(byte) * x ) ; for( i = 0 ; i < x-1 ; i++ ) { scanf("%d", &y ) ; a[i] = y ; } Both y and x are initialized. X is the size of the array determined by the user. The segmentation fault is on the second to last integer to be added, i found this by adding printf("roar") ; before setting a[i] to y and entering one number at a time. Byte is a typedef of an unsigned char. Note: I've also tried using a[i] = (byte)y ; A is ininitalized as follows byte *a ; If you need to view the entire code it is this: #include <stdio.h> #include <stdlib.h> #include "sort.h" int p_cmp_f () ; int main( int argc, char *argv[] ) { int x, y, i, choice ; byte *a ; while( choice !=2 ) { printf( "Would you like to sort integers?\n1. Yes\n2. No\n" ) ; scanf("%d", &choice ) ; switch(choice) { case 1: printf( "Enter the length of the array: " ) ; scanf( "%d", &x ) ; a = (byte *)malloc(sizeof( byte ) * x ) ; printf( "Enter %d integers to add to the array: ", x ) ; for( i = 0 ; i < x -1 ; i++ ) { scanf( "%d", &y ) ; a[i] = y ; } switch( choice ) { case 1: bubble_sort( a, x, sizeof(int), p_cmp_f ) ; for( i = 0 ; i < x ; i++ ) printf( "%d", a[i] ; break ; case 2: selection_sort( a, x, sizeof(int), p_cmp_f ) ; for( i = 0 ; i < x; i++ ) printf( "%d", a[i] ; break ; case 3: insertion_sort( a, x, sizeof(int), p_cmp_f ) ; for( i = 0 ; i < x ; i++ ) printf( "%d", a[i] ; break ; case 4: merge_sort( a, x, sizeof(int), p_cmp_f ) ; for( i = 0 ; i < x ; i++ ) printf( "%d", a[i] ; break ; case 5: quick_sort( a, x, sizeof(int), p_cmp_f ) ; for( i = 0 ; i < x ; i++ ) printf( "%d", a[i] ; break ; default: printf("Enter either 1,2,3,4, or 5" ) ; break ; } case 2: printf( "Thank you for using this program\n" ) ; return 0 ; break ; default: printf( "Enter either 1 or 2: " ) ; break ; } } free(a) ; return 0 ; } int p_cmp_f( byte *element1, byte *element2 ) { return *((int *)element1) - *((int *)element2) ; }

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  • C Program not running as intended, hangs after input

    - by user41419
    The program I am writing to take a number and display that number as a calculator would display it (shown below) is compiling with no issues, but when I try to run it, I am able to input my number, but nothing happens. It seems like it is "hanging", since no further output is shown as I would have expected. Might anyone know what the problem is? #include <stdio.h> #define MAX_DIGITS 20 char segments[10][7] = /* seven segment array */ {{'1','1','1','1','1','1','0'}, /* zero */ {'0','1','1','0','0','0','0'}, /* one */ {'1','1','0','1','1','0','1'}, /* two */ {'1','1','1','1','0','0','1'}, /* three */ {'0','1','1','0','0','1','1'}, /* four */ {'1','0','1','1','0','1','1'}, /* five */ {'1','0','1','1','1','1','1'}, /* six */ {'1','1','1','0','0','0','0'}, /* seven */ {'1','1','1','1','1','1','1'}, /* eight */ {'1','1','1','0','0','1','1'}};/* nine */ char digits[3][MAX_DIGITS * 4]; /* digits array */ int i, j; /* count variables */ int adjust; /* output formatting */ int main(void) { clear_digits_array(); int digit[20]; for (i = 0; i < 20; i++) { digit[i] = 0; } int count = 20; int position = 0; printf("Enter a number: "); int number = scanf("%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d", &digit[0], &digit[1], &digit[2], &digit[3], &digit[4], &digit[5], &digit[6], &digit[7], &digit[8], &digit[9], &digit[10], &digit[11], &digit[12], &digit[13], &digit[14], &digit[15], &digit[16], &digit[17], &digit[18], &digit[19]); //NOTHING HAPPENS AFTER HERE printf("Got input, number is %d", number); while (count > 0) { printf("Reading digits, count is %d", count); process_digit(digit[20 - count], position); position++; count--; } print_digits_array(); printf("\n"); return 0; } void clear_digits_array(void) { /* fill all positions in digits array with blank spaces */ for (i = 0; i < 3; i++) { for (j = 0; j < (MAX_DIGITS * 4); j++) { digits[i][j] = ' '; } } } void process_digit(int digit, int position) { /* check each segment to see if segment should be filled in for given digit */ for (i = 0; i < 7; i++) { printf("Processing digit %d at position %d, i is %d", digit, position, i); if (segments[digit][i] == 1) { switch (i) { case 0: digits[0][(position * 4) + 1] = '_'; break; case 1: digits[1][(position * 4) + 2] = '|'; break; case 2: digits[2][(position * 4) + 2] = '|'; break; case 3: digits[2][(position * 4) + 1] = '_'; break; case 4: digits[2][(position * 4) + 0] = '|'; break; case 5: digits[1][(position * 4) + 0] = '|'; break; case 6: digits[1][(position * 4) + 1] = '_'; break; } } } } void print_digits_array(void) { /* print each character in digits array */ for (i = 0; i < 3; i++) { for (j = 0; j < (MAX_DIGITS * 4); j++) { printf("%c", digits[i][j]); } printf("/n"); } }

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  • Runtime error in C code (strange double conversion)

    - by Miro Hassan
    I have a strange runtime error in my C code. The Integers comparison here works fine. But in the Decimals comparison, I always get that the second number is larger than the first number, which is false. I am pretty new to C and programming in general, so this is a complex application to me. #include <stdio.h> #include <stdbool.h> #include <stdlib.h> int choose; long long neLimit = -1000000000; long long limit = 1000000000; bool big(a,b) { if ((a >= limit) || (b >= limit)) return true; else if ((a <= neLimit) || (b <= neLimit)) return true; return false; } void largerr(a,b) { if (a > b) printf("\nThe First Number is larger ..\n"); else if (a < b) printf("\nThe Second Number is larger ..\n"); else printf("\nThe Two Numbers are Equal .. \n"); } int main() { system("color e && title Numbers Comparison && echo off && cls"); start:{ printf("Choose a Type of Comparison :\n\t1. Integers\n\t2. Decimals \n\t\t I Choose Number : "); scanf("%i", &choose); switch(choose) { case 1: goto Integers; break; case 2: goto Decimals; break; default: system("echo Please Choose a Valid Option && pause>nul && cls"); goto start; } } Integers: { system("title Integers Comparison && cls"); long x , y; printf("\nFirst Number : \t"); scanf("%li", &x); printf("\nSecond Number : "); scanf("%li", &y); if (big(x,y)) { printf("\nOut of Limit .. Too Big Numbers ..\n"); system("pause>nul && cls") ; goto Integers; } largerr(x,y); printf("\nFirst Number : %li\nSecond Number : %li\n",x,y); goto exif; } Decimals: { system("title Decimals Comparison && cls"); double x , y; printf("\nFirst Number : \t"); scanf("%le", &x); printf("\nSecond Number : "); scanf("%le", &y); if (big(x,y)) { printf("\nOut of Limit .. Too Big Numbers ..\n"); system("pause>nul && cls") ; goto Decimals; } largerr(x,y); goto exif; } exif:{ system("pause>nul"); system("cls"); main(); } }

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  • Generating 2-dimensional vla ends in segmentation fault

    - by Framester
    Hi, further developing the code from yesterday (seg fault caused by malloc and sscanf in a function), I tried with the help of some tutorials I found on the net to generate a 2-dim vla. But I get a segmentation fault at (*data)[i][j]=atof(p);. The program is supposed to read a matrix out of a text file and load it into a 2d array (cols 1-9) and a 1D array (col 10) [Example code] #include<stdio.h> #include<stdlib.h> #include<math.h> #include<string.h> const int LENGTH = 1024; void read_data(float ***data, int **classes, int *nrow,int *ncol, char *filename){ FILE *pfile = NULL; char line[LENGTH]; if(!( pfile=fopen(filename,"r"))){ printf("Error opening %s.", filename); exit(1); } int numlines=0; int numcols=0; char *p; fgets(line,LENGTH,pfile); p = strtok (line," "); while (p != NULL){ p = strtok (NULL, ", "); numcols++; } while(fgets(line,LENGTH,pfile)){ numlines++; } rewind(pfile); int numfeats=numcols-1; *data=(float**) malloc(numlines*sizeof(float*)); *classes=(int *)malloc(numlines*sizeof(int)); if(*classes == NULL){ printf("\nOut of memory."); exit(1); } int i=0; while(fgets(line,LENGTH,pfile)){ p = strtok (line," "); for(int j=0;j<numfeats;j++) { (data)[i]=malloc(numfeats*sizeof(float)); printf("%i ",i); (*data)[i][j]=atof(p); p = strtok (NULL, ", "); } (*classes)[i]=atoi(p); i++; } fclose(pfile); *nrow=numlines; *ncol=numfeats; } int main() { char *filename="somedatafile.txt"; float **data2; int *classes2; int r,c; read_data(&data2,&classes2, &r, &c,filename) ; for(int i=0;i<r;i++){ printf("\n"); for(int j=0;j<c;j++){ printf("%f",data2[i][j]); } } return 1; } [Content of somedatafile.txt] 50 21 77 0 28 0 27 48 22 2 55 0 92 0 0 26 36 92 56 4 53 0 82 0 52 -5 29 30 2 1 37 0 76 0 28 18 40 48 8 1 37 0 79 0 34 -26 43 46 2 1 85 0 88 -4 6 1 3 83 80 5 56 0 81 0 -4 11 25 86 62 4 55 -1 95 -3 54 -4 40 41 2 1 53 8 77 0 28 0 23 48 24 4 37 0 101 -7 28 0 64 73 8 1 ...

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  • segmentation fault using scanf

    - by agarrow
    noob question here: I'm trying to write a simple menu interface, but I keep getting a segmentation fault error and I can't figure out why. #include <stdlib.h> #include <stdio.h> int flush(); int add(char *name, char *password, char *type); int delete(char *name); int edit(char *name, char *password, char *type, char *newName, char *newPassword, char *newType); int verify(char *name, char *password); int menu(){ int input; char *name, *password, *type, *newName, *newPassword, *newType; printf("MAIN MENU \n ============\n"); printf("1. ADD\n"); printf("2. DELETE\n"); printf("3. EDIT\n"); printf("4. VERIFY\n"); printf("5. Exit\n"); printf("Selection:"); scanf("%d", &input); flush(); switch (input){ case 1: printf("%s\n", "Enter Name:"); scanf("%s", name); flush(); printf("%s\n", "enter password" ); scanf("%s", password); flush(); printf("%s\n","enter type" ); scanf("%s",type); add(name, password, type); menu(); break; case 2: printf("Enter Name:" ); scanf("%s",name); flush(); delete(name); menu(); break; case 3: printf("Enter Name:\n"); scanf("%s",name); flush(); printf("Enter Password\n"); scanf("%s", password); flush(); printf("enter type:\n"); scanf("%s", type); flush(); printf("enter your new username:\n"); scanf("%s",newName); flush(); printf("enter your new password\n"); scanf("%s", newPassword); flush(); printf("enter your new type\n"); scanf("%s",newType); flush(); edit(name, password, type, newName, newPassword, newType); menu(); break; case 4: printf("Enter Name\n"); scanf("%s",name); flush(); printf("Enter Password\n"); scanf("%s",password); flush(); verify(name, password); menu(); break; case 5: return 0; default: printf("invalid input, please select from the following:\n"); menu(); } return 0; } int flush(){ int ch; while ((ch = getchar()) != EOF && ch != '\n') ; return 0; } I get the segmentation fault after entering two fields, in any menu option

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  • Nested loop traversing arrays

    - by alecco
    There are 2 very big series of elements, the second 100 times bigger than the first. For each element of the first series, there are 0 or more elements on the second series. This can be traversed and processed with 2 nested loops. But the unpredictability of the amount of matching elements for each member of the first array makes things very, very slow. The actual processing of the 2nd series of elements involves logical and (&) and a population count. I couldn't find good optimizations using C but I am considering doing inline asm, doing rep* mov* or similar for each element of the first series and then doing the batch processing of the matching bytes of the second series, perhaps in buffers of 1MB or something. But the code would be get quite messy. Does anybody know of a better way? C preferred but x86 ASM OK too. Many thanks! Sample/demo code with simplified problem, first series are "people" and second series are "events", for clarity's sake. (the original problem is actually 100m and 10,000m entries!) #include <stdio.h> #include <stdint.h> #define PEOPLE 1000000 // 1m struct Person { uint8_t age; // Filtering condition uint8_t cnt; // Number of events for this person in E } P[PEOPLE]; // Each has 0 or more bytes with bit flags #define EVENTS 100000000 // 100m uint8_t P1[EVENTS]; // Property 1 flags uint8_t P2[EVENTS]; // Property 2 flags void init_arrays() { for (int i = 0; i < PEOPLE; i++) { // just some stuff P[i].age = i & 0x07; P[i].cnt = i % 220; // assert( sum < EVENTS ); } for (int i = 0; i < EVENTS; i++) { P1[i] = i % 7; // just some stuff P2[i] = i % 9; // just some other stuff } } int main(int argc, char *argv[]) { uint64_t sum = 0, fcur = 0; int age_filter = 7; // just some init_arrays(); // Init P, P1, P2 for (int64_t p = 0; p < PEOPLE ; p++) if (P[p].age < age_filter) for (int64_t e = 0; e < P[p].cnt ; e++, fcur++) sum += __builtin_popcount( P1[fcur] & P2[fcur] ); else fcur += P[p].cnt; // skip this person's events printf("(dummy %ld %ld)\n", sum, fcur ); return 0; } gcc -O5 -march=native -std=c99 test.c -o test

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  • Sending typedef struct containing void* by creating MPI drived datatype.

    - by hankol
    what I understand studying MPI specification is that an MPI send primitive refer to a memory location (or a send buffer) pointed by the data to be sent and take the data in that location which then passed as a message to the another Process. Though it is true that virtual address of a give process will be meaningless in another process memory address; It is ok to send data pointed by pointer such as void pointer as MPI will any way pass the data itself as a message For example the following works correctly: // Sender Side. int x = 100; void* snd; MPI_Send(snd,4,MPI_BYTE,1,0,MPI_COMM_WORLD); // Receiver Side. void* rcv; MPI_Recv(rcv, 4,MPI_BYTE,0,0,MPI_COMM_WORLD); but when I add void* snd in a struct and try to send the struct this will no succeed. I don't understand why the previous example work correctly but not the following. Here, I have defined a typedef struct and then create an MPI_DataType from it. With the same explanation of the above the following should also have succeed, unfortunately it is not working. here is the code: #include "mpi.h" #include<stdio.h> int main(int args, char *argv[]) { int rank, source =0, tag=1, dest=1; int bloackCount[2]; MPI_Init(&args, &argv); typedef struct { void* data; int tag; } data; data myData; MPI_Datatype structType, oldType[2]; MPI_Status stat; /* MPI_Aint type used to idetify byte displacement of each block (array)*/ MPI_Aint offsets[2], extent; MPI_Comm_rank(MPI_COMM_WORLD, &rank); offsets[0] = 0; oldType[0] = MPI_BYTE; bloackCount[0] = 1; MPI_Type_extent(MPI_INT, &extent); offsets[1] = 4 * extent; /*let say the MPI_BYTE will contain ineteger : size of int * extent */ oldType[1] = MPI_INT; bloackCount[1] = 1; MPI_Type_create_struct(2, bloackCount,offsets,oldType, &structType); MPI_Type_commit(&structType); if(rank == 0){ int x = 100; myData.data = &x; myData.tag = 99; MPI_Send(&myData,1,structType, dest, tag, MPI_COMM_WORLD); } if(rank == 1 ){ MPI_Recv(&myData, 1, structType, source, tag, MPI_COMM_WORLD, &stat); // with out this the following printf() will properly print the value 99 for // myData.tag int x = *(int *) myData.data; printf(" \n Process %d, Received : %d , %d \n\n", rank , myData.tag, x); } MPI_Type_free(&structType); MPI_Finalize(); } Error message running the code: [Looks like I am trying to access an invalid memory address space in the second process] [ubuntu:04123] *** Process received signal *** [ubuntu:04123] Signal: Segmentation fault (11) [ubuntu:04123] Signal code: Address not mapped (1) [ubuntu:04123] Failing at address: 0xbfe008bc [ubuntu:04123] [ 0] [0xb778240c] [ubuntu:04123] [ 1] GenericstructType(main+0x161) [0x8048935] [ubuntu:04123] [ 2] /lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf3) [0xb750f4d3] [ubuntu:04123] [ 3] GenericstructType() [0x8048741] [ubuntu:04123] *** End of error message *** Can some please explain to me why it is not working. any advice will also be appreciated thanks,

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  • about getadrrinfo() C++?

    - by Isavel
    I'm reading this book called beej's guide to network programming and there's a part in the book were it provide a sample code which illustrate the use of getaddrinfo(); the book state that the code below "will print the IP addresses for whatever host you specify on the command line" - beej's guide to network programming. now I'm curious and want to try it out and run the code, but I guess the code was develop in UNIX environment and I'm using visual studio 2012 windows 7 OS, and most of the headers was not supported so I did a bit of research and find out that I need to include the winsock.h and ws2_32.lib for windows, for it to get working, fortunately everything compiled no errors, but when I run it using the debugger and put in 'www.google.com' as command argument I was disappointed that it did not print any ipaddress, the output that I got from the console is "getaddrinfo: E" what does the letter E mean? Do I need to configure something out of the debugger? Interestingly I left the command argument blank and the output changed to "usage: showip hostname" Any help would be appreciated. #ifdef _WIN32 #endif #include <sys/types.h> #include <winsock2.h> #include <ws2tcpip.h> #include <iostream> using namespace std; #include <stdio.h> #include <string.h> #include <sys/types.h> #include <winsock.h> #pragma comment(lib, "ws2_32.lib") int main(int argc, char *argv[]) { struct addrinfo hints, *res, *p; int status; char ipstr[INET6_ADDRSTRLEN]; if (argc != 2) { fprintf(stderr,"usage: showip hostname\n"); system("PAUSE"); return 1; } memset(&hints, 0, sizeof hints); hints.ai_family = AF_UNSPEC; // AF_INET or AF_INET6 to force version hints.ai_socktype = SOCK_STREAM; if ((status = getaddrinfo(argv[1], NULL, &hints, &res)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(status)); system("PAUSE"); return 2; } printf("IP addresses for %s:\n\n", argv[1]); for(p = res;p != NULL; p = p->ai_next) { void *addr; char *ipver; // get the pointer to the address itself, // different fields in IPv4 and IPv6: if (p->ai_family == AF_INET) { // IPv4 struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr; addr = &(ipv4->sin_addr); ipver = "IPv4"; } else { // IPv6 struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr; addr = &(ipv6->sin6_addr); ipver = "IPv6"; } // convert the IP to a string and print it: inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr); printf(" %s: %s\n", ipver, ipstr); } freeaddrinfo(res); // free the linked list system("PAUSE"); return 0; }

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  • C - Error with read() of a file, storage in an array, and printing output properly

    - by ns1
    I am new to C, so I am not exactly sure where my error is. However, I do know that the great portion of the issue lies either in how I am storing the doubles in the d_buffer (double) array or the way I am printing it. Specifically, my output keeps printing extremely large numbers (with around 10-12 digits before the decimal point and a trail of zeros after it. Additionally, this is an adaptation of an older program to allow for double inputs, so I only really added the two if statements (in the "read" for loop and the "printf" for loop) and the d_buffer declaration. I would appreciate any input whatsoever as I have spent several hours on this error. #include <stdio.h> #include <fcntl.h> #include <sys/types.h> #include <unistd.h> #include <string.h> struct DataDescription { char fieldname[30]; char fieldtype; int fieldsize; }; /* ----------------------------------------------- eof(fd): returns 1 if file `fd' is out of data ----------------------------------------------- */ int eof(int fd) { char c; if ( read(fd, &c, 1) != 1 ) return(1); else { lseek(fd, -1, SEEK_CUR); return(0); } } void main() { FILE *fp; /* Used to access meta data */ int fd; /* Used to access user data */ /* ---------------------------------------------------------------- Variables to hold the description of the data - max 10 fields ---------------------------------------------------------------- */ struct DataDescription DataDes[10]; /* Holds data descriptions for upto 10 fields */ int n_fields; /* Actual # fields */ /* ------------------------------------------------------ Variables to hold the data - max 10 fields.... ------------------------------------------------------ */ char c_buffer[10][100]; /* For character data */ int i_buffer[10]; /* For integer data */ double d_buffer[10]; int i, j; int found; printf("Program for searching a mini database:\n"); /* ============================= Read in meta information ============================= */ fp = fopen("db-description", "r"); n_fields = 0; while ( fscanf(fp, "%s %c %d", DataDes[n_fields].fieldname, &DataDes[n_fields].fieldtype, &DataDes[n_fields].fieldsize) > 0 ) n_fields++; /* --- Prints meta information --- */ printf("\nThe database consists of these fields:\n"); for (i = 0; i < n_fields; i++) printf("Index %d: Fieldname `%s',\ttype = %c,\tsize = %d\n", i, DataDes[i].fieldname, DataDes[i].fieldtype, DataDes[i].fieldsize); printf("\n\n"); /* --- Open database file --- */ fd = open("db-data", O_RDONLY); /* --- Print content of the database file --- */ printf("\nThe database content is:\n"); while ( ! eof(fd) ) { /* ------------------ Read next record ------------------ */ for (j = 0; j < n_fields; j++) { if ( DataDes[j].fieldtype == 'I' ) read(fd, &i_buffer[j], DataDes[j].fieldsize); if ( DataDes[j].fieldtype == 'F' ) read(fd, &d_buffer[j], DataDes[j].fieldsize); if ( DataDes[j].fieldtype == 'C' ) read(fd, &c_buffer[j], DataDes[j].fieldsize); } double d; /* ------------------ Print it... ------------------ */ for (j = 0; j < n_fields; j++) { if ( DataDes[j].fieldtype == 'I' ) printf("%d ", i_buffer[j]); if ( DataDes[j].fieldtype == 'F' ) d = d_buffer[j]; printf("%lf ", d); if ( DataDes[j].fieldtype == 'C' ) printf("%s ", c_buffer[j]); } printf("\n"); } printf("\n"); printf("\n"); } Post edits output: 16777216 0.000000 107245694331284094976.000000 107245694331284094976.000000 Pi 33554432 107245694331284094976.000000 2954938175610156848888276006519501238173891974277081114627768841840801736306392481516295906896346039950625609765296207682724801406770458881439696544971142710292689518104183685723154223544599940711614138798312668264956190761622328617992192.000000 2954938175610156848888276006519501238173891974277081114627768841840801736306392481516295906896346039950625609765296207682724801406770458881439696544971142710292689518104183685723154223544599940711614138798312668264956190761622328617992192.000000 Secret Key 50331648 2954938175610156848888276006519501238173891974277081114627768841840801736306392481516295906896346039950625609765296207682724801406770458881439696544971142710292689518104183685723154223544599940711614138798312668264956190761622328617992192.000000 -0.000000 -0.000000 The number E Expected Output: 3 rows of data ending with the number "e = 2.18281828" To reproduce the problem, the following two files need to be in the same directory as the lookup-data.c file: - db-data - db-description

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  • Elfsign Object Signing on Solaris

    - by danx
    Elfsign Object Signing on Solaris Don't let this happen to you—use elfsign! Solaris elfsign(1) is a command that signs and verifies ELF format executables. That includes not just executable programs (such as ls or cp), but other ELF format files including libraries (such as libnvpair.so) and kernel modules (such as autofs). Elfsign has been available since Solaris 10 and ELF format files distributed with Solaris, since Solaris 10, are signed by either Sun Microsystems or its successor, Oracle Corporation. When an ELF file is signed, elfsign adds a new section the ELF file, .SUNW_signature, that contains a RSA public key signature and other information about the signer. That is, the algorithm used, algorithm OID, signer CN/OU, and time stamp. The signature section can later be verified by elfsign or other software by matching the signature in the file agains the ELF file contents (excluding the signature). ELF executable files may also be signed by a 3rd-party or by the customer. This is useful for verifying the origin and authenticity of executable files installed on a system. The 3rd-party or customer public key certificate should be installed in /etc/certs/ to allow verification by elfsign. For currently-released versions of Solaris, only cryptographic framework plugin libraries are verified by Solaris. However, all ELF files may be verified by the elfsign command at any time. Elfsign Algorithms Elfsign signatures are created by taking a digest of the ELF section contents, then signing the digest with RSA. To verify, one takes a digest of ELF file and compares with the expected digest that's computed from the signature and RSA public key. Originally elfsign took a MD5 digest of a SHA-1 digest of the ELF file sections, then signed the resulting digest with RSA. In Solaris 11.1 then Solaris 11.1 SRU 7 (5/2013), the elfsign crypto algorithms available have been expanded to keep up with evolving cryptography. The following table shows the available elfsign algorithms: Elfsign Algorithm Solaris Release Comments elfsign sign -F rsa_md5_sha1   S10, S11.0, S11.1 Default for S10. Not recommended* elfsign sign -F rsa_sha1 S11.1 Default for S11.1. Not recommended elfsign sign -F rsa_sha256 S11.1 patch SRU7+   Recommended ___ *Most or all CAs do not accept MD5 CSRs and do not issue MD5 certs due to MD5 hash collision problems. RSA Key Length. I recommend using RSA-2048 key length with elfsign is RSA-2048 as the best balance between a long expected "life time", interoperability, and performance. RSA-2048 keys have an expected lifetime through 2030 (and probably beyond). For details, see Recommendation for Key Management: Part 1: General, NIST Publication SP 800-57 part 1 (rev. 3, 7/2012, PDF), tables 2 and 4 (pp. 64, 67). Step 1: create or obtain a key and cert The first step in using elfsign is to obtain a key and cert from a public Certificate Authority (CA), or create your own self-signed key and cert. I'll briefly explain both methods. Obtaining a Certificate from a CA To obtain a cert from a CA, such as Verisign, Thawte, or Go Daddy (to name a few random examples), you create a private key and a Certificate Signing Request (CSR) file and send it to the CA, following the instructions of the CA on their website. They send back a signed public key certificate. The public key cert, along with the private key you created is used by elfsign to sign an ELF file. The public key cert is distributed with the software and is used by elfsign to verify elfsign signatures in ELF files. You need to request a RSA "Class 3 public key certificate", which is used for servers and software signing. Elfsign uses RSA and we recommend RSA-2048 keys. The private key and CSR can be generated with openssl(1) or pktool(1) on Solaris. Here's a simple example that uses pktool to generate a private RSA_2048 key and a CSR for sending to a CA: $ pktool gencsr keystore=file format=pem outcsr=MYCSR.p10 \ subject="CN=canineswworks.com,OU=Canine SW object signing" \ outkey=MYPRIVATEKEY.key $ openssl rsa -noout -text -in MYPRIVATEKEY.key Private-Key: (2048 bit) modulus: 00:d2:ef:42:f2:0b:8c:96:9f:45:32:fc:fe:54:94: . . . [omitted for brevity] . . . c9:c7 publicExponent: 65537 (0x10001) privateExponent: 26:14:fc:49:26:bc:a3:14:ee:31:5e:6b:ac:69:83: . . . [omitted for brevity] . . . 81 prime1: 00:f6:b7:52:73:bc:26:57:26:c8:11:eb:6c:dc:cb: . . . [omitted for brevity] . . . bc:91:d0:40:d6:9d:ac:b5:69 prime2: 00:da:df:3f:56:b2:18:46:e1:89:5b:6c:f1:1a:41: . . . [omitted for brevity] . . . f3:b7:48:de:c3:d9:ce:af:af exponent1: 00:b9:a2:00:11:02:ed:9a:3f:9c:e4:16:ce:c7:67: . . . [omitted for brevity] . . . 55:50:25:70:d3:ca:b9:ab:99 exponent2: 00:c8:fc:f5:57:11:98:85:8e:9a:ea:1f:f2:8f:df: . . . [omitted for brevity] . . . 23:57:0e:4d:b2:a0:12:d2:f5 coefficient: 2f:60:21:cd:dc:52:76:67:1a:d8:75:3e:7f:b0:64: . . . [omitted for brevity] . . . 06:94:56:d8:9d:5c:8e:9b $ openssl req -noout -text -in MYCSR.p10 Certificate Request: Data: Version: 2 (0x2) Subject: OU=Canine SW object signing, CN=canineswworks.com Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:d2:ef:42:f2:0b:8c:96:9f:45:32:fc:fe:54:94: . . . [omitted for brevity] . . . c9:c7 Exponent: 65537 (0x10001) Attributes: Signature Algorithm: sha1WithRSAEncryption b3:e8:30:5b:88:37:68:1c:26:6b:45:af:5e:de:ea:60:87:ea: . . . [omitted for brevity] . . . 06:f9:ed:b4 Secure storage of RSA private key. The private key needs to be protected if the key signing is used for production (as opposed to just testing). That is, protect the key to protect against unauthorized signatures by others. One method is to use a PIN-protected PKCS#11 keystore. The private key you generate should be stored in a secure manner, such as in a PKCS#11 keystore using pktool(1). Otherwise others can sign your signature. Other secure key storage mechanisms include a SCA-6000 crypto card, a USB thumb drive stored in a locked area, a dedicated server with restricted access, Oracle Key Manager (OKM), or some combination of these. I also recommend secure backup of the private key. Here's an example of generating a private key protected in the PKCS#11 keystore, and a CSR. $ pktool setpin # use if PIN not set yet Enter token passphrase: changeme Create new passphrase: Re-enter new passphrase: Passphrase changed. $ pktool gencsr keystore=pkcs11 label=MYPRIVATEKEY \ format=pem outcsr=MYCSR.p10 \ subject="CN=canineswworks.com,OU=Canine SW object signing" $ pktool list keystore=pkcs11 Enter PIN for Sun Software PKCS#11 softtoken: Found 1 asymmetric public keys. Key #1 - RSA public key: MYPRIVATEKEY Here's another example that uses openssl instead of pktool to generate a private key and CSR: $ openssl genrsa -out cert.key 2048 $ openssl req -new -key cert.key -out MYCSR.p10 Self-Signed Cert You can use openssl or pktool to create a private key and a self-signed public key certificate. A self-signed cert is useful for development, testing, and internal use. The private key created should be stored in a secure manner, as mentioned above. The following example creates a private key, MYSELFSIGNED.key, and a public key cert, MYSELFSIGNED.pem, using pktool and displays the contents with the openssl command. $ pktool gencert keystore=file format=pem serial=0xD06F00D lifetime=20-year \ keytype=rsa hash=sha256 outcert=MYSELFSIGNED.pem outkey=MYSELFSIGNED.key \ subject="O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com" $ pktool list keystore=file objtype=cert infile=MYSELFSIGNED.pem Found 1 certificates. 1. (X.509 certificate) Filename: MYSELFSIGNED.pem ID: c8:24:59:08:2b:ae:6e:5c:bc:26:bd:ef:0a:9c:54:de:dd:0f:60:46 Subject: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Issuer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Not Before: Oct 17 23:18:00 2013 GMT Not After: Oct 12 23:18:00 2033 GMT Serial: 0xD06F00D0 Signature Algorithm: sha256WithRSAEncryption $ openssl x509 -noout -text -in MYSELFSIGNED.pem Certificate: Data: Version: 3 (0x2) Serial Number: 3496935632 (0xd06f00d0) Signature Algorithm: sha256WithRSAEncryption Issuer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Validity Not Before: Oct 17 23:18:00 2013 GMT Not After : Oct 12 23:18:00 2033 GMT Subject: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:bb:e8:11:21:d9:4b:88:53:8b:6c:5a:7a:38:8b: . . . [omitted for brevity] . . . bf:77 Exponent: 65537 (0x10001) Signature Algorithm: sha256WithRSAEncryption 9e:39:fe:c8:44:5c:87:2c:8f:f4:24:f6:0c:9a:2f:64:84:d1: . . . [omitted for brevity] . . . 5f:78:8e:e8 $ openssl rsa -noout -text -in MYSELFSIGNED.key Private-Key: (2048 bit) modulus: 00:bb:e8:11:21:d9:4b:88:53:8b:6c:5a:7a:38:8b: . . . [omitted for brevity] . . . bf:77 publicExponent: 65537 (0x10001) privateExponent: 0a:06:0f:23:e7:1b:88:62:2c:85:d3:2d:c1:e6:6e: . . . [omitted for brevity] . . . 9c:e1:e0:0a:52:77:29:4a:75:aa:02:d8:af:53:24: c1 prime1: 00:ea:12:02:bb:5a:0f:5a:d8:a9:95:b2:ba:30:15: . . . [omitted for brevity] . . . 5b:ca:9c:7c:19:48:77:1e:5d prime2: 00:cd:82:da:84:71:1d:18:52:cb:c6:4d:74:14:be: . . . [omitted for brevity] . . . 5f:db:d5:5e:47:89:a7:ef:e3 exponent1: 32:37:62:f6:a6:bf:9c:91:d6:f0:12:c3:f7:04:e9: . . . [omitted for brevity] . . . 97:3e:33:31:89:66:64:d1 exponent2: 00:88:a2:e8:90:47:f8:75:34:8f:41:50:3b:ce:93: . . . [omitted for brevity] . . . ff:74:d4:be:f3:47:45:bd:cb coefficient: 4d:7c:09:4c:34:73:c4:26:f0:58:f5:e1:45:3c:af: . . . [omitted for brevity] . . . af:01:5f:af:ad:6a:09:bf Step 2: Sign the ELF File object By now you should have your private key, and obtained, by hook or crook, a cert (either from a CA or use one you created (a self-signed cert). The next step is to sign one or more objects with your private key and cert. Here's a simple example that creates an object file, signs, verifies, and lists the contents of the ELF signature. $ echo '#include <stdio.h>\nint main(){printf("Hello\\n");}'>hello.c $ make hello cc -o hello hello.c $ elfsign verify -v -c MYSELFSIGNED.pem -e hello elfsign: no signature found in hello. $ elfsign sign -F rsa_sha256 -v -k MYSELFSIGNED.key -c MYSELFSIGNED.pem -e hello elfsign: hello signed successfully. format: rsa_sha256. signer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com. signed on: October 17, 2013 04:22:49 PM PDT. $ elfsign list -f format -e hello rsa_sha256 $ elfsign list -f signer -e hello O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com $ elfsign list -f time -e hello October 17, 2013 04:22:49 PM PDT $ elfsign verify -v -c MYSELFSIGNED.key -e hello elfsign: verification of hello failed. format: rsa_sha256. signer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com. signed on: October 17, 2013 04:22:49 PM PDT. Signing using the pkcs11 keystore To sign the ELF file using a private key in the secure pkcs11 keystore, replace "-K MYSELFSIGNED.key" in the "elfsign sign" command line with "-T MYPRIVATEKEY", where MYPRIVATKEY is the pkcs11 token label. Step 3: Install the cert and test on another system Just signing the object isn't enough. You need to copy or install the cert and the signed ELF file(s) on another system to test that the signature is OK. Your public key cert should be installed in /etc/certs. Use elfsign verify to verify the signature. Elfsign verify checks each cert in /etc/certs until it finds one that matches the elfsign signature in the file. If one isn't found, the verification fails. Here's an example: $ su Password: # rm /etc/certs/MYSELFSIGNED.key # cp MYSELFSIGNED.pem /etc/certs # exit $ elfsign verify -v hello elfsign: verification of hello passed. format: rsa_sha256. signer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com. signed on: October 17, 2013 04:24:20 PM PDT. After testing, package your cert along with your ELF object to allow elfsign verification after your cert and object are installed or copied. Under the Hood: elfsign verification Here's the steps taken to verify a ELF file signed with elfsign. The steps to sign the file are similar except the private key exponent is used instead of the public key exponent and the .SUNW_signature section is written to the ELF file instead of being read from the file. Generate a digest (SHA-256) of the ELF file sections. This digest uses all ELF sections loaded in memory, but excludes the ELF header, the .SUNW_signature section, and the symbol table Extract the RSA signature (RSA-2048) from the .SUNW_signature section Extract the RSA public key modulus and public key exponent (65537) from the public key cert Calculate the expected digest as follows:     signaturepublicKeyExponent % publicKeyModulus Strip the PKCS#1 padding (most significant bytes) from the above. The padding is 0x00, 0x01, 0xff, 0xff, . . ., 0xff, 0x00. If the actual digest == expected digest, the ELF file is verified (OK). Further Information elfsign(1), pktool(1), and openssl(1) man pages. "Signed Solaris 10 Binaries?" blog by Darren Moffat (2005) shows how to use elfsign. "Simple CLI based CA on Solaris" blog by Darren Moffat (2008) shows how to set up a simple CA for use with self-signed certificates. "How to Create a Certificate by Using the pktool gencert Command" System Administration Guide: Security Services (available at docs.oracle.com)

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  • CUDA linking error - Visual Express 2008 - nvcc fatal due to (null) configuration file

    - by Josh
    Hi, I've been searching extensively for a possible solution to my error for the past 2 weeks. I have successfully installed the Cuda 64-bit compiler (tools) and SDK as well as the 64-bit version of Visual Studio Express 2008 and Windows 7 SDK with Framework 3.5. I'm using windows XP 64-bit. I have confirmed that VSE is able to compile in 64-bit as I have all of the 64-bit options available to me using the steps on the following website: (since Visual Express does not inherently include the 64-bit packages) http://jenshuebel.wordpress.com/2009/02/12/visual-c-2008-express-edition-and-64-bit-targets/ I have confirmed the 64-bit compile ability since the "x64" is available from the pull-down menu under "Tools-Options-VC++ Directories" and compiling in 64-bit does not result in the entire project being "skipped". I have included all the needed directories for 64-bit cuda tools, 64 SDK and Visual Express (\VC\bin\amd64). Here's the error message I receive when trying to compile in 64-bit: 1>------ Build started: Project: New, Configuration: Release x64 ------ 1>Compiling with CUDA Build Rule... 1>"C:\CUDA\bin64\nvcc.exe" -arch sm_10 -ccbin "C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\bin" -Xcompiler "/EHsc /W3 /nologo /O2 /Zi /MT " -maxrregcount=32 --compile -o "x64\Release\template.cu.obj" "c:\Documents and Settings\All Users\Application Data\NVIDIA Corporation\NVIDIA GPU Computing SDK\C\src\CUDA_Walkthrough_DeviceKernels\template.cu" 1>nvcc fatal : Visual Studio configuration file '(null)' could not be found for installation at 'C:/Program Files (x86)/Microsoft Visual Studio 9.0/VC/bin/../..' 1>Linking... 1>LINK : fatal error LNK1181: cannot open input file '.\x64\Release\template.cu.obj' 1>Build log was saved at "file://c:\Documents and Settings\Administrator\My Documents\Visual Studio 2008\Projects\New\New\x64\Release\BuildLog.htm" 1>New - 1 error(s), 0 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== Here's the simple code I'm trying to compile/run in 64-bit: #include <stdlib.h> #include <stdio.h> #include <string.h> #include <math.h> #include <cuda.h> void mypause () { printf ( "Press [Enter] to continue . . ." ); fflush ( stdout ); getchar(); } __global__ void VecAdd1_Kernel(float* A, float* B, float* C, int N) { int i = blockDim.x*blockIdx.x+threadIdx.x; if (i<N) C[i] = A[i] + B[i]; //result should be a 16x1 array of 250s } __global__ void VecAdd2_Kernel(float* B, float* C, int N) { int i = blockDim.x*blockIdx.x+threadIdx.x; if (i<N) C[i] = C[i] + B[i]; //result should be a 16x1 array of 400s } int main() { int N = 16; float A[16];float B[16]; size_t size = N*sizeof(float); for(int i=0; i<N; i++) { A[i] = 100.0; B[i] = 150.0; } // Allocate input vectors h_A and h_B in host memory float* h_A = (float*)malloc(size); float* h_B = (float*)malloc(size); float* h_C = (float*)malloc(size); //Initialize Input Vectors memset(h_A,0,size);memset(h_B,0,size); h_A = A;h_B = B; printf("SUM = %f\n",A[1]+B[1]); //simple check for initialization //Allocate vectors in device memory float* d_A; cudaMalloc((void**)&d_A,size); float* d_B; cudaMalloc((void**)&d_B,size); float* d_C; cudaMalloc((void**)&d_C,size); //Copy vectors from host memory to device memory cudaMemcpy(d_A,h_A,size,cudaMemcpyHostToDevice); cudaMemcpy(d_B,h_B,size,cudaMemcpyHostToDevice); //Invoke kernel int threadsPerBlock = 256; int blocksPerGrid = (N+threadsPerBlock-1)/threadsPerBlock; VecAdd1(blocksPerGrid, threadsPerBlock,d_A,d_B,d_C,N); VecAdd2(blocksPerGrid, threadsPerBlock,d_B,d_C,N); //Copy results from device memory to host memory //h_C contains the result in host memory cudaMemcpy(h_C,d_C,size,cudaMemcpyDeviceToHost); for(int i=0; i<N; i++) //output result from the kernel "VecAdd" { printf("%f ", h_C[i] ); printf("\n"); } printf("\n"); cudaFree(d_A); cudaFree(d_B); cudaFree(d_C); free(h_A); free(h_B); free(h_C); mypause(); return 0; }

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  • how to clear stack after stack overflow signal occur

    - by user353573
    In pthread, After reaching yellow zone in stack, signal handler stop the recursive function by making it return however, we can only continue to use extra area in yellow zone, how to clear the rubbish before the yellow zone in the thread stack ? (Copied from "answers"): #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <signal.h> #include <setjmp.h> #include <sys/mman.h> #include <unistd.h> #include <assert.h> #include <sys/resource.h> #define ALT_STACK_SIZE (64*1024) #define YELLOW_ZONE_PAGES (1) typedef struct { size_t stack_size; char* stack_pointer; char* red_zone_boundary; char* yellow_zone_boundary; sigjmp_buf return_point; size_t red_zone_size; } ThreadInfo; static pthread_key_t thread_info_key; static struct sigaction newAct, oldAct; bool gofromyellow = false; int call_times = 0; static void main_routine(){ // make it overflow if(gofromyellow == true) { printf("return from yellow zone, called %d times\n", call_times); return; } else { call_times = call_times + 1; main_routine(); gofromyellow = true; } } // red zone management static void stackoverflow_routine(){ fprintf(stderr, "stack overflow error.\n"); fflush(stderr); } // yellow zone management static void yellow_zone_hook(){ fprintf(stderr, "exceed yellow zone.\n"); fflush(stderr); } static int get_stack_info(void** stackaddr, size_t* stacksize){ int ret = -1; pthread_attr_t attr; pthread_attr_init(&attr); if(pthread_getattr_np(pthread_self(), &attr) == 0){ ret = pthread_attr_getstack(&attr, stackaddr, stacksize); } pthread_attr_destroy(&attr); return ret; } static int is_in_stack(const ThreadInfo* tinfo, char* pointer){ return (tinfo->stack_pointer <= pointer) && (pointer < tinfo->stack_pointer + tinfo->stack_size); } static int is_in_red_zone(const ThreadInfo* tinfo, char* pointer){ if(tinfo->red_zone_boundary){ return (tinfo->stack_pointer <= pointer) && (pointer < tinfo->red_zone_boundary); } } static int is_in_yellow_zone(const ThreadInfo* tinfo, char* pointer){ if(tinfo->yellow_zone_boundary){ return (tinfo->red_zone_boundary <= pointer) && (pointer < tinfo->yellow_zone_boundary); } } static void set_yellow_zone(ThreadInfo* tinfo){ int pagesize = sysconf(_SC_PAGE_SIZE); assert(pagesize > 0); tinfo->yellow_zone_boundary = tinfo->red_zone_boundary + pagesize * YELLOW_ZONE_PAGES; mprotect(tinfo->red_zone_boundary, pagesize * YELLOW_ZONE_PAGES, PROT_NONE); } static void reset_yellow_zone(ThreadInfo* tinfo){ size_t pagesize = tinfo->yellow_zone_boundary - tinfo->red_zone_boundary; if(mmap(tinfo->red_zone_boundary, pagesize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0) == 0){ perror("mmap failed"), exit(1); } mprotect(tinfo->red_zone_boundary, pagesize, PROT_READ | PROT_WRITE); tinfo->yellow_zone_boundary = 0; } static void signal_handler(int sig, siginfo_t* sig_info, void* sig_data){ if(sig == SIGSEGV){ ThreadInfo* tinfo = (ThreadInfo*) pthread_getspecific(thread_info_key); char* fault_address = (char*) sig_info->si_addr; if(is_in_stack(tinfo, fault_address)){ if(is_in_red_zone(tinfo, fault_address)){ siglongjmp(tinfo->return_point, 1); }else if(is_in_yellow_zone(tinfo, fault_address)){ reset_yellow_zone(tinfo); yellow_zone_hook(); gofromyellow = true; return; } else { //inside stack not related overflow SEGV happen } } } } static void register_application_info(){ pthread_key_create(&thread_info_key, NULL); sigemptyset(&newAct.sa_mask); sigaddset(&newAct.sa_mask, SIGSEGV); newAct.sa_sigaction = signal_handler; newAct.sa_flags = SA_SIGINFO | SA_RESTART | SA_ONSTACK; sigaction(SIGSEGV, &newAct, &oldAct); } static void register_thread_info(ThreadInfo* tinfo){ stack_t ss; pthread_setspecific(thread_info_key, tinfo); get_stack_info((void**)&tinfo->stack_pointer, &tinfo->stack_size); printf("stack size %d mb\n", tinfo->stack_size/1024/1024 ); tinfo->red_zone_boundary = tinfo->stack_pointer + tinfo->red_zone_size; set_yellow_zone(tinfo); ss.ss_sp = (char*)malloc(ALT_STACK_SIZE); ss.ss_size = ALT_STACK_SIZE; ss.ss_flags = 0; sigaltstack(&ss, NULL); } static void* thread_routine(void* p){ ThreadInfo* tinfo = (ThreadInfo*)p; register_thread_info(tinfo); if(sigsetjmp(tinfo->return_point, 1) == 0){ main_routine(); } else { stackoverflow_routine(); } free(tinfo); printf("after tinfo, end thread\n"); return 0; } int main(int argc, char** argv){ register_application_info(); if( argc == 2 ){ int stacksize = atoi(argv[1]); pthread_attr_t attr; pthread_attr_init(&attr); pthread_attr_setstacksize(&attr, 1024 * 1024 * stacksize); { pthread_t pid0; ThreadInfo* tinfo = (ThreadInfo*)calloc(1, sizeof(ThreadInfo)); pthread_attr_getguardsize(&attr, &tinfo->red_zone_size); pthread_create(&pid0, &attr, thread_routine, tinfo); pthread_join(pid0, NULL); } } else { printf("Usage: %s stacksize(mb)\n", argv[0]); } return 0; } C language in linux, ubuntu

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  • Faulting DLL (ISAPI Filter)...

    - by Brad
    I wrote this ISAPI filter to rewrite the URL because we had some sites that moved locations... Basically the filter looks at the referrer, and if it's the local server, it looks at the requested URL and compared it to the full referrer. If the first path is identical, nothing is done, however if not, it takes the first path from the full referrer and prepends it to the URL. For example: /Content/imgs/img.jpg from a referrer of http://myserver/wr/apps/default.htm would be rewritten as /wr/Content/imgs/img.jpg. When I view the log file, everything looks good. However the DLL keeps faulting with the following information: Faulting application w3wp.exe, version 6.0.3790.3959, faulting module URLRedirector.dll, version 0.0.0.0, fault address 0x0002df25. Here's the code: #include <windows.h> #include <stdio.h> #include <stdlib.h> #include <httpfilt.h> #include <time.h> #include <string.h> #ifdef _DEBUG #define TO_FILE // uncomment out to use a log file #ifdef TO_FILE #define DEST ghFile #define DebugMsg(x) WriteToFile x; HANDLE ghFile; #define LOGFILE "W:\\Temp\\URLRedirector.log" void WriteToFile (HANDLE hFile, char *szFormat, ...) { char szBuf[1024]; DWORD dwWritten; va_list list; va_start (list, szFormat); vsprintf (szBuf, szFormat, list); hFile = CreateFile (LOGFILE, GENERIC_WRITE, 0, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL); if (hFile != INVALID_HANDLE_VALUE) { SetFilePointer (hFile, 0, NULL, FILE_END); WriteFile (hFile, szBuf, lstrlen (szBuf), &dwWritten, NULL); CloseHandle (hFile); } va_end (list); } #endif #endif BOOL WINAPI __stdcall GetFilterVersion(HTTP_FILTER_VERSION *pVer) { /* Specify the types and order of notification */ pVer->dwFlags = (SF_NOTIFY_ORDER_HIGH | SF_NOTIFY_SECURE_PORT | SF_NOTIFY_NONSECURE_PORT | SF_NOTIFY_PREPROC_HEADERS | SF_NOTIFY_END_OF_NET_SESSION); pVer->dwFilterVersion = HTTP_FILTER_REVISION; strcpy(pVer->lpszFilterDesc, "URL Redirector, Version 1.0"); return TRUE; } DWORD WINAPI __stdcall HttpFilterProc(HTTP_FILTER_CONTEXT *pfc, DWORD NotificationType, VOID *pvData) { CHAR *pPhysPath; PHTTP_FILTER_URL_MAP pURLMap; PHTTP_FILTER_PREPROC_HEADERS pHeaderInfo; CHAR szReferrer[255], szServer[255], szURL[255], szNewURL[255]; DWORD dwRSize = sizeof(szReferrer); DWORD dwSSize = sizeof(szServer); DWORD dwUSize = sizeof(szURL); int iTmp, iTmp2; CHAR *pos, tmp[255], *tmp2; switch (NotificationType) { case SF_NOTIFY_PREPROC_HEADERS : pHeaderInfo = (PHTTP_FILTER_PREPROC_HEADERS)pvData; if (pfc->GetServerVariable(pfc, "HTTP_REFERER", szReferrer, &dwRSize)) { DebugMsg(( DEST, "Referrer: %s\r\n", szReferrer )); if (pfc->GetServerVariable(pfc, "SERVER_NAME", szServer, &dwSSize)) DebugMsg(( DEST, "Server Name: %s\r\n", szServer )); if (pHeaderInfo->GetHeader(pfc, "URL", szURL, &dwUSize)) DebugMsg(( DEST, "URL: %s\r\n", szURL )); iTmp = strnstr(szReferrer, szServer, strlen(szReferrer)); if(iTmp > 0) { //Referred is our own server... strcpy(tmp, szReferrer + iTmp); DebugMsg(( DEST, "tmp: %s - %d\r\n", tmp, strlen(tmp) )); pos = strchr(tmp+1, '/'); DebugMsg(( DEST, "pos: %s - %d\r\n", pos, strlen(pos) )); iTmp2 = strlen(tmp) - strlen(pos) + 1; strncpy(tmp2, tmp, iTmp2); tmp2[iTmp2] = '\0'; DebugMsg(( DEST, "tmp2: %s\r\n", tmp2)); if(strncmp(szURL, tmp2, iTmp2) != 0) { //First paths don't match, create new URL... strncpy(szNewURL, tmp2, iTmp2-1); strcat(szNewURL, szURL); DebugMsg(( DEST, "newURL: %s\r\n", szNewURL)); pHeaderInfo->SetHeader(pfc, "URL", szNewURL); return SF_STATUS_REQ_HANDLED_NOTIFICATION; } } } break; default : break; } return SF_STATUS_REQ_NEXT_NOTIFICATION; } /* simple function to compare two strings and return the position at which the compare ended */ static int strnstr ( const char *string, const char *strCharSet, int n) { int len = (strCharSet != NULL ) ? ((int)strlen(strCharSet )) : 0 ; int ret, I, J, found; if ( 0 == n || 0 == len ) { return -1; } ret = -1; found = 0; for (I = 0 ; I <= n - len && found != 1 ; I++) { J = 0 ; for ( ; J < len ; J++ ) { if (toupper(string[I + J]) != toupper(strCharSet [J])) { break; // Exit For(J) } } if ( J == len) { ret = I + (J); found = 1; } } return ret; }

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  • Thread scheduling Round Robin / scheduling dispatch

    - by MRP
    #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <semaphore.h> #define NUM_THREADS 4 #define COUNT_LIMIT 13 int done = 0; int count = 0; int quantum = 2; int thread_ids[4] = {0,1,2,3}; int thread_runtime[4] = {0,5,4,7}; pthread_mutex_t count_mutex; pthread_cond_t count_threshold_cv; void * inc_count(void * arg); static sem_t count_sem; int quit = 0; ///////// Inc_Count//////////////// void *inc_count(void *t) { long my_id = (long)t; int i; sem_wait(&count_sem); /////////////CRIT SECTION////////////////////////////////// printf("run_thread = %d\n",my_id); printf("%d \n",thread_runtime[my_id]); for( i=0; i < thread_runtime[my_id];i++) { printf("runtime= %d\n",thread_runtime[my_id]); pthread_mutex_lock(&count_mutex); count++; if (count == COUNT_LIMIT) { pthread_cond_signal(&count_threshold_cv); printf("inc_count(): thread %ld, count = %d Threshold reached.\n", my_id, count); } printf("inc_count(): thread %ld, count = %d, unlocking mutex\n",my_id, count); pthread_mutex_unlock(&count_mutex); sleep(1) ; }//End For sem_post(&count_sem); // Next Thread Enters Crit Section pthread_exit(NULL); } /////////// Count_Watch //////////////// void *watch_count(void *t) { long my_id = (long)t; printf("Starting watch_count(): thread %ld\n", my_id); pthread_mutex_lock(&count_mutex); if (count<COUNT_LIMIT) { pthread_cond_wait(&count_threshold_cv, &count_mutex); printf("watch_count(): thread %ld Condition signal received.\n", my_id); printf("watch_count(): thread %ld count now = %d.\n", my_id, count); } pthread_mutex_unlock(&count_mutex); pthread_exit(NULL); } ////////////////// Main //////////////// int main (int argc, char *argv[]) { int i; long t1=0, t2=1, t3=2, t4=3; pthread_t threads[4]; pthread_attr_t attr; sem_init(&count_sem, 0, 1); /* Initialize mutex and condition variable objects */ pthread_mutex_init(&count_mutex, NULL); pthread_cond_init (&count_threshold_cv, NULL); /* For portability, explicitly create threads in a joinable state */ pthread_attr_init(&attr); pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE); pthread_create(&threads[0], &attr, watch_count, (void *)t1); pthread_create(&threads[1], &attr, inc_count, (void *)t2); pthread_create(&threads[2], &attr, inc_count, (void *)t3); pthread_create(&threads[3], &attr, inc_count, (void *)t4); /* Wait for all threads to complete */ for (i=0; i<NUM_THREADS; i++) { pthread_join(threads[i], NULL); } printf ("Main(): Waited on %d threads. Done.\n", NUM_THREADS); /* Clean up and exit */ pthread_attr_destroy(&attr); pthread_mutex_destroy(&count_mutex); pthread_cond_destroy(&count_threshold_cv); pthread_exit(NULL); } I am trying to learn thread scheduling, there is a lot of technical coding that I don't know. I do know in theory how it should work, but having trouble getting started in code... I know, at least I think, this program is not real time and its not meant to be. Some how I need to create a scheduler dispatch to control the threads in the order they should run... RR FCFS SJF ect. Right now I don't have a dispatcher. What I do have is semaphores/ mutex to control the threads. This code does run FCFS... and I have been trying to use semaphores to create a RR.. but having a lot of trouble. I believe it would be easier to create a dispatcher but I dont know how. I need help, I am not looking for answers just direction.. some sample code will help to understand a bit more. Thank you.

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  • Reference a GNU C (POSIX) DLL built in GCC against Cygwin, from C#/NET

    - by Dale Halliwell
    Here is what I want: I have a huge legacy C/C++ codebase written for POSIX, including some very POSIX specific stuff like pthreads. This can be compiled on Cygwin/GCC and run as an executable under Windows with the Cygwin DLL. What I would like to do is build the codebase itself into a Windows DLL that I can then reference from C# and write a wrapper around it to access some parts of it programatically. I have tried this approach with the very simple "hello world" example at http://www.cygwin.com/cygwin-ug-net/dll.html and it doesn't seem to work. #include <stdio.h> extern "C" __declspec(dllexport) int hello(); int hello() { printf ("Hello World!\n"); return 42; } I believe I should be able to reference a DLL built with the above code in C# using something like: [DllImport("kernel32.dll")] public static extern IntPtr LoadLibrary(string dllToLoad); [DllImport("kernel32.dll")] public static extern IntPtr GetProcAddress(IntPtr hModule, string procedureName); [DllImport("kernel32.dll")] public static extern bool FreeLibrary(IntPtr hModule); [UnmanagedFunctionPointer(CallingConvention.Cdecl)] private delegate int hello(); static void Main(string[] args) { var path = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "helloworld.dll"); IntPtr pDll = LoadLibrary(path); IntPtr pAddressOfFunctionToCall = GetProcAddress(pDll, "hello"); hello hello = (hello)Marshal.GetDelegateForFunctionPointer( pAddressOfFunctionToCall, typeof(hello)); int theResult = hello(); Console.WriteLine(theResult.ToString()); bool result = FreeLibrary(pDll); Console.ReadKey(); } But this approach doesn't seem to work. LoadLibrary returns null. It can find the DLL (helloworld.dll), it is just like it can't load it or find the exported function. I am sure that if I get this basic case working I can reference the rest of my codebase in this way. Any suggestions or pointers, or does anyone know if what I want is even possible? Thanks. Edit: Examined my DLL with Dependency Walker (great tool, thanks) and it seems to export the function correctly. Question: should I be referencing it as the function name Dependency Walker seems to find (_Z5hellov)? Edit2: Just to show you I have tried it, linking directly to the dll at relative or absolute path (i.e. not using LoadLibrary): [DllImport(@"C:\.....\helloworld.dll")] public static extern int hello(); static void Main(string[] args) { int theResult = hello(); Console.WriteLine(theResult.ToString()); Console.ReadKey(); } This fails with: "Unable to load DLL 'C:.....\helloworld.dll': Invalid access to memory location. (Exception from HRESULT: 0x800703E6) *Edit 3: * Oleg has suggested running dumpbin.exe on my dll, this is the output: Dump of file helloworld.dll File Type: DLL Section contains the following exports for helloworld.dll 00000000 characteristics 4BD5037F time date stamp Mon Apr 26 15:07:43 2010 0.00 version 1 ordinal base 1 number of functions 1 number of names ordinal hint RVA name 1 0 000010F0 hello Summary 1000 .bss 1000 .data 1000 .debug_abbrev 1000 .debug_info 1000 .debug_line 1000 .debug_pubnames 1000 .edata 1000 .eh_frame 1000 .idata 1000 .reloc 1000 .text Edit 4 Thanks everyone for the help, I managed to get it working. Oleg's answer gave me the information I needed to find out what I was doing wrong. There are 2 ways to do this. One is to build with the gcc -mno-cygwin compiler flag, which builds the dll without the cygwin dll, basically as if you had built it in MingW. Building it this way got my hello world example working! However, MingW doesn't have all the libraries that cygwin has in the installer, so if your POSIX code has dependencies on these libraries (mine had heaps) you can't do this way. And if your POSIX code didn't have those dependencies, why not just build for Win32 from the beginning. So that's not much help unless you want to spend time setting up MingW properly. The other option is to build with the Cygwin DLL. The Cygwin DLL needs an initialization function init() to be called before it can be used. This is why my code wasn't working before. The code below loads and runs my hello world example. //[DllImport(@"hello.dll", EntryPoint = "#1",SetLastError = true)] //static extern int helloworld(); //don't do this! cygwin needs to be init first [DllImport("kernel32", CharSet = CharSet.Ansi, ExactSpelling = true, SetLastError = true)] static extern IntPtr GetProcAddress(IntPtr hModule, string procName); [DllImport("kernel32", SetLastError = true)] static extern IntPtr LoadLibrary(string lpFileName); public delegate int MyFunction(); static void Main(string[] args) { //load cygwin dll IntPtr pcygwin = LoadLibrary("cygwin1.dll"); IntPtr pcyginit = GetProcAddress(pcygwin, "cygwin_dll_init"); Action init = (Action)Marshal.GetDelegateForFunctionPointer(pcyginit, typeof(Action)); init(); IntPtr phello = LoadLibrary("hello.dll"); IntPtr pfn = GetProcAddress(phello, "helloworld"); MyFunction helloworld = (MyFunction)Marshal.GetDelegateForFunctionPointer(pfn, typeof(MyFunction)); Console.WriteLine(helloworld()); Console.ReadKey(); } Thanks to everyone that answered~~

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  • Ethernet Communication Error

    - by SivaKumar
    Hi, I wrote a program to query the status of the Ethernet printer for that i created a TCP Stream Socket and i send the query command to the printer.In case of Error less condition it returns No error status but in error case its getting hang at recv command.Even i used Non blocking now the recv command returns nothing and error set as Resource temporarily unavailable. code: #include <stdio.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <netdb.h> #include <string.h> #include <unistd.h> #include <arpa/inet.h> #include <errno.h> #include <stdlib.h> #include <fcntl.h> #include <sys/ioctl.h> #include <sys/socket.h> #include <signal.h> #include <termios.h> #include <poll.h> #include <netinet/tcp.h> #include <stdarg.h> int main() { int ConnectSocket,ConnectSocket1,select_err,err,nRet,nBytesRead; struct timeval waitTime = {10,30}; fd_set socket_set; unsigned char * dataBuf = NULL; unsigned char tempVar, tempVar1, tempVar2, tempVar3; char reset[] = "\033E 2\r"; char print[] = "\033A 1\r"; char buf[1024]={0}; ConnectSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); printf("The Socket ID is %d\n",ConnectSocket); if (ConnectSocket < 0) { perror("socket()"); return 0; } struct sockaddr_in clientService; clientService.sin_family = AF_INET; clientService.sin_addr.s_addr = inet_addr("192.168.0.129"); //Printer IP clientService.sin_port = htons( 9100); // Printer Port if ( connect( ConnectSocket, (struct sockaddr*) &clientService, sizeof(clientService) ) == -1) { perror("connect()"); close(ConnectSocket); return -1; } /* if((nRet = ioctl(ConnectSocket , FIONREAD, &nBytesRead) == -1)) { perror("ioctl()"); } perror("ioctl()"); */ FD_ZERO(&socket_set); FD_SET(ConnectSocket, &socket_set); do { errno=0; select_err = select(ConnectSocket+1, NULL, &socket_set, NULL, &waitTime); }while(errno==EINPROGRESS); if (-1 == select_err || 0 == select_err) { int optVal = 0; int optLen = sizeof(optVal); if(select_err == -1) { perror("select() write-side"); } else { //Timeout errno=0; err = getsockopt(ConnectSocket, SOL_SOCKET, SO_ERROR, (char*)&optVal, &optLen); printf("the return of the getsockopt is %d\n",err); printf("the opt val is %s\n",(char*)optVal); perror("getsockopt()"); if(err == -1) { perror("getsockopt() write-side"); } } printf("Select Failed during write - ConnectSocket: %d\n", ConnectSocket); //close(ConnectSocket); return -1; } err = send(ConnectSocket,print,sizeof(print)-1, 0); printf("\n No of Bytes Send is %d\n",err); if(err == -1 || err ==0) { perror("send()"); //close(ConnectSocket); return -1; } FD_ZERO(&socket_set); FD_SET(ConnectSocket, &socket_set); do { errno=0; select_err = select(ConnectSocket+1, NULL, &socket_set, NULL, &waitTime); }while(errno==EINPROGRESS); if (-1 == select_err || 0 == select_err) { printf("Select Failed during write - ConnectSocket: %d\n", ConnectSocket); return -1; } err = send(ConnectSocket,reset,sizeof(reset)-1, 0); printf("\n No of Bytes Send is %d\n",err); if(err == -1 || err ==0) { perror("send()"); //close(ConnectSocket); return -1; } FD_ZERO(&socket_set); FD_SET(ConnectSocket, &socket_set); printf("i am in reading \n"); select_err = select(ConnectSocket+1, &socket_set, NULL, NULL, &waitTime); printf("the retun of the read side select is %d \n",select_err); perror("select()"); if (-1 == select_err|| 0 == select_err) { printf("Read timeout; ConnectSocket: %d\n", ConnectSocket); close(ConnectSocket); perror("close()"); return -1; } printf("Before Recv\n"); nBytesRead = recv(ConnectSocket , buf, 1024, 0); printf("No of Bytes read is %d\n",nBytesRead); printf("%s\n",buf); if(nBytesRead == -1) { perror("recv()"); close(ConnectSocket); perror("clode()"); return -1; } close(ConnectSocket); return 1; }

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  • Help with malloc and free: Glibc detected: free(): invalid pointer

    - by nunos
    I need help with debugging this piece of code. I know the problem is in malloc and free but can't find exactly where, why and how to fix it. Please don't answer: "Use gdb" and that's it. I would use gdb to debug it, but I still don't know much about it and am still learning it, and would like to have, in the meanwhile, another solution. Thanks. #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <unistd.h> #include <string.h> #include <sys/wait.h> #include <sys/types.h> #define MAX_COMMAND_LENGTH 256 #define MAX_ARGS_NUMBER 128 #define MAX_HISTORY_NUMBER 100 #define PROMPT ">>> " int num_elems; typedef enum {false, true} bool; typedef struct { char **arg; char *infile; char *outfile; int background; } Command_Info; int parse_cmd(char *cmd_line, Command_Info *cmd_info) { char *arg; char *args[MAX_ARGS_NUMBER]; int i = 0; arg = strtok(cmd_line, " "); while (arg != NULL) { args[i] = arg; arg = strtok(NULL, " "); i++; } num_elems = i;precisa em free_mem if (num_elems == 0) return 0; cmd_info->arg = (char **) ( malloc(num_elems * sizeof(char *)) ); cmd_info->infile = NULL; cmd_info->outfile = NULL; cmd_info->background = 0; bool b_infile = false; bool b_outfile = false; int iarg = 0; for (i = 0; i < num_elems; i++) { if ( !strcmp(args[i], "<") ) { if ( b_infile || i == num_elems-1 || !strcmp(args[i+1], "<") || !strcmp(args[i+1], ">") || !strcmp(args[i+1], "&") ) return -1; i++; cmd_info->infile = malloc(strlen(args[i]) * sizeof(char)); strcpy(cmd_info->infile, args[i]); b_infile = true; } else if (!strcmp(args[i], ">")) { if ( b_outfile || i == num_elems-1 || !strcmp(args[i+1], ">") || !strcmp(args[i+1], "<") || !strcmp(args[i+1], "&") ) return -1; i++; cmd_info->outfile = malloc(strlen(args[i]) * sizeof(char)); strcpy(cmd_info->outfile, args[i]); b_outfile = true; } else if (!strcmp(args[i], "&")) { if ( i == 0 || i != num_elems-1 || cmd_info->background ) return -1; cmd_info->background = true; } else { cmd_info->arg[iarg] = malloc(strlen(args[i]) * sizeof(char)); strcpy(cmd_info->arg[iarg], args[i]); iarg++; } } cmd_info->arg[iarg] = NULL; return 0; } void print_cmd(Command_Info *cmd_info) { int i; for (i = 0; cmd_info->arg[i] != NULL; i++) printf("arg[%d]=\"%s\"\n", i, cmd_info->arg[i]); printf("arg[%d]=\"%s\"\n", i, cmd_info->arg[i]); printf("infile=\"%s\"\n", cmd_info->infile); printf("outfile=\"%s\"\n", cmd_info->outfile); printf("background=\"%d\"\n", cmd_info->background); } void get_cmd(char* str) { fgets(str, MAX_COMMAND_LENGTH, stdin); str[strlen(str)-1] = '\0'; } pid_t exec_simple(Command_Info *cmd_info) { pid_t pid = fork(); if (pid < 0) { perror("Fork Error"); return -1; } if (pid == 0) { if ( (execvp(cmd_info->arg[0], cmd_info->arg)) == -1) { perror(cmd_info->arg[0]); exit(1); } } return pid; } void type_prompt(void) { printf("%s", PROMPT); } void syntax_error(void) { printf("msh syntax error\n"); } void free_mem(Command_Info *cmd_info) { int i; for (i = 0; cmd_info->arg[i] != NULL; i++) free(cmd_info->arg[i]); free(cmd_info->arg); free(cmd_info->infile); free(cmd_info->outfile); } int main(int argc, char* argv[]) { char cmd_line[MAX_COMMAND_LENGTH]; Command_Info cmd_info; //char* history[MAX_HISTORY_NUMBER]; while (true) { type_prompt(); get_cmd(cmd_line); if ( parse_cmd(cmd_line, &cmd_info) == -1) { syntax_error(); continue; } if (!strcmp(cmd_line, "")) continue; if (!strcmp(cmd_info.arg[0], "exit")) exit(0); pid_t pid = exec_simple(&cmd_info); waitpid(pid, NULL, 0); free_mem(&cmd_info); } return 0; }

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  • strange output in ubuntu terminal when running a lex program

    - by Max
    Hi. I'm running a lexical analyzer using lex, and I've got it mostly correct, but my terminal gives strange output once I take out an ECHO statement I was using to help debug the code. With that statement, my output looks like this: max@Max-Ubuntu:~/Desktop/Compiler Project/project2$ ./a.out <../cmmFiles/expression.cmm VOIDID(){ INTID,ID,ID; BOOLID,ID,ID; ID(ID); ID(ID); ID(ID); ID(ID); ID=-ID-NUM+ID/NUM*(-NUM+ID*IDNUM); ID(ID); ID=ID>ID||ID>=ID; IF(ID)ID(NUM);ELSEID(NUM); ID=ID<ID&&ID<=ID; IF(ID==TRUE)ID(NUM);ELSEID(NUM); ID=ID&&!ID||!ID&&ID; IF(ID!=FALSE)ID(NUM);ELSEID(NUM); } While hard to read, that output is correct. Once I take out the ECHO statement, I instead get this: max@Max-Ubuntu:~/Desktop/Compiler Project/project2$ ./a.out <../cmmFiles/expression.cmm }F(ID!=FALSE)ID(NUM);ELSEID(NUM);; It looks like it's only outputting the final line, except with an extraneous } near the beginning, what looks like half an IF token immediately after, and an extraneous ; at the end. Is this some quirk of my terminal, or does removing that ECHO cause my lexer to screw up that badly? I'm hesitant to keep working until I know for sure what's going on here. Thanks for any answers. Here's my lexer: %{ /* definitions of manifest constants -reserved words- BOOL, ELSE, IF, TRUE, WHILE, DO, FALSE, INT, VOID -Punctuation and operators- LPAREN, RPAREN, LBRACK, RBRACK, LBRACE, RBRACE, SEMI, COMMA, PLUS, MINUS, TIMES, DIV, MOD, AND, OR, NOT, IS, ADDR, EQ, NE, LT, GT, LE, GE -Other tokens- NUMBER, ID, PUNCT, OP */ #include <stdio.h> #include <stdlib.h> //#include "y.tab.h" //int line = 1, numAttr; //char *strAttr; %} /* regular definitions */ delim [ \t] ws {delim}+ start "/*" one [^*] two "*" three [^*/] end "/" comment {start}({one}*{two}+{three})*{one}*{two}+{end} letter [A-Za-z] digit [0-9] id ({letter}|_)({letter}|{digit}|_)* number {digit}+ %% {ws} { /*no action and no return */} {comment} { /*no action and no return */} [\n] {ECHO; /*no action */} // <-- this is the ECHO in question. bool { printf("BOOL");} else { printf("ELSE");} if { printf("IF");} true { printf("TRUE");} while { printf("WHILE");} do { printf("DO");} false { printf("FALSE");} int { printf("INT");} void { printf("VOID");} {id} { printf("ID");} {number} { printf("NUM");} "(" { printf("(");} ")" { printf(")");} "[" { printf("[");} "]" { printf("]");} "{" { printf("{");} "}" { printf("}");} ";" { printf(";");} "," { printf(",");} "+" { printf("+");} "-" { printf("-");} "*" { printf("*");} "/" { printf("/");} "%" { printf("%");} "&" { printf("&");} "&&" { printf("&&");} "||" { printf("||");} "!" { printf("!");} "!=" { printf("!=");} "=" { printf("=");} "==" { printf("==");} "<" { printf("<");} "<=" { printf("<=");} ">" { printf(">");} ">=" { printf(">=");} %% int main() { yylex(); printf("\n"); } int yywrap(void) { return 1; } here's the file it's analyzing: /* this program * illustrates evaluation of * arithmetic and boolean * expressions */ void main( ) { int m,n,p; bool a,b,c; scan(m); print(m); scan(n); print(n); p=-m-3+n/2*(-5+m*n%4); print(p); a=m>n || n>=p; if (a) print(1); else print(0); b=m<n && n<=p; if (b==true) print(1); else print(0); c=a && !b || !a && b; if (c!=false) print(1); else print(0); }

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  • C question: Padding bits in unsigned integers and bitwise operations (C89)

    - by Anonymous Question Guy
    I have a lot of code that performs bitwise operations on unsigned integers. I wrote my code with the assumption that those operations were on integers of fixed width without any padding bits. For example an array of 32 bit unsigned integers of which all 32 bits available for each integer. I'm looking to make my code more portable and I'm focused on making sure I'm C89 compliant (in this case). One of the issues that I've come across is possible padded integers. Take this extreme example, taken from the GMP manual: However on Cray vector systems it may be noted that short and int are always stored in 8 bytes (and with sizeof indicating that) but use only 32 or 46 bits. The nails feature can account for this, by passing for instance 8*sizeof(int)-INT_BIT. I've also read about this type of padding in other places. I actually read of a post on SO last night (forgive me, I don't have the link and I'm going to cite something similar from memory) where if you have, say, a double with 60 usable bits the other 4 could be used for padding and those padding bits could serve some internal purpose so they cannot be modified. So let's say for example my code is compiled on a platform where an unsigned int type is sized at 4 bytes, each byte being 8 bits, however the most significant 2 bits are padding bits. Would UINT_MAX in that case be 0x3FFFFFFF (1073741823) ? #include <stdio.h> #include <stdlib.h> /* padding bits represented by underscores */ int main( int argc, char **argv ) { unsigned int a = 0x2AAAAAAA; /* __101010101010101010101010101010 */ unsigned int b = 0x15555555; /* __010101010101010101010101010101 */ unsigned int c = a ^ b; /* ?? __111111111111111111111111111111 */ unsigned int d = c << 5; /* ?? __111111111111111111111111100000 */ unsigned int e = d >> 5; /* ?? __000001111111111111111111111111 */ printf( "a: %X\nb: %X\nc: %X\nd: %X\ne: %X\n", a, b, c, d, e ); return 0; } is it safe to XOR two integers with padding bits? wouldn't I XOR whatever the padding bits are? I can't find this behavior covered in C89. furthermore is the c var guaranteed to be 0x3FFFFFFF or if for example the two padding bits were both on in a or b would c be 0xFFFFFFFF ? same question with d and e. am i manipulating the padding bits by shifting? I would expect to see this below, assuming 32 bits with the 2 most significant bits used for padding, but I want to know if something like this is guaranteed: a: 2AAAAAAA b: 15555555 c: 3FFFFFFF d: 3FFFFFE0 e: 01FFFFFF Also are padding bits always the most significant bits or could they be the least significant bits? Thanks guys EDIT 12/19/2010 5PM EST: Christoph has answered my question. Thanks! I had also asked (above) whether padding bits are always the most significant bits. This is cited in the rationale for the C99 standard, and the answer is no. I am playing it safe and assuming the same for C89. Here is specifically what the C99 rationale says for §6.2.6.2 (Representation of Integer Types): Padding bits are user-accessible in an unsigned integer type. For example, suppose a machine uses a pair of 16-bit shorts (each with its own sign bit) to make up a 32-bit int and the sign bit of the lower short is ignored when used in this 32-bit int. Then, as a 32-bit signed int, there is a padding bit (in the middle of the 32 bits) that is ignored in determining the value of the 32-bit signed int. But, if this 32-bit item is treated as a 32-bit unsigned int, then that padding bit is visible to the user’s program. The C committee was told that there is a machine that works this way, and that is one reason that padding bits were added to C99. Footnotes 44 and 45 mention that parity bits might be padding bits. The committee does not know of any machines with user-accessible parity bits within an integer. Therefore, the committee is not aware of any machines that treat parity bits as padding bits. EDIT 12/28/2010 3PM EST: I found an interesting discussion on comp.lang.c from a few months ago. Bitwise Operator Effects on Padding Bits (VelocityReviews reader) Bitwise Operator Effects on Padding Bits (Google Groups alternate link) One point made by Dietmar which I found interesting: Let's note that padding bits are not necessary for the existence of trap representations; combinations of value bits which do not represent a value of the object type would also do.

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  • Why does this XML validation via XSD fail in libxml2 (but succeed in xmllint) and how do I fix it?

    - by mtree
    If I run this XML validation via xmllint: xmllint --noout --schema schema.xsd test.xml I get this success message: .../test.xml validates However if I run the same validation via libxml2's C API: int result = xmlSchemaValidateDoc(...) I get a return value of 1845 and this failure message: Element '{http://example.com/XMLSchema/1.0}foo': No matching global declaration available for the validation root. Which I can make absolutely no sense of. :( schema.xsd: <?xml version="1.0" encoding="utf-8" ?> <!DOCTYPE xs:schema PUBLIC "-//W3C//DTD XMLSCHEMA 200102//EN" "XMLSchema.dtd" > <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="http://example.com/XMLSchema/1.0" targetNamespace="http://example.com/XMLSchema/1.0" elementFormDefault="qualified" attributeFormDefault="unqualified"> <xs:element name="foo"> </xs:element> </xs:schema> test.xml: <?xml version="1.0" encoding="UTF-8"?> <foo xmlns="http://example.com/XMLSchema/1.0"> </foo> main.c: #include <stdio.h> #include <sys/stat.h> #include <sys/types.h> #include <string.h> #include <libxml/parser.h> #include <libxml/valid.h> #include <libxml/xmlschemas.h> u_int32_t get_file_size(const char *file_name) { struct stat buf; if ( stat(file_name, &buf) != 0 ) return(0); return (unsigned int)buf.st_size; } void handleValidationError(void *ctx, const char *format, ...) { char *errMsg; va_list args; va_start(args, format); vasprintf(&errMsg, format, args); va_end(args); fprintf(stderr, "Validation Error: %s", errMsg); free(errMsg); } int main (int argc, const char * argv[]) { const char *xsdPath = argv[1]; const char *xmlPath = argv[2]; printf("\n"); printf("XSD File: %s\n", xsdPath); printf("XML File: %s\n", xmlPath); int xmlLength = get_file_size(xmlPath); char *xmlSource = (char *)malloc(sizeof(char) * xmlLength); FILE *p = fopen(xmlPath, "r"); char c; unsigned int i = 0; while ((c = fgetc(p)) != EOF) { xmlSource[i++] = c; } printf("\n"); printf("XML Source:\n\n%s\n", xmlSource); fclose(p); printf("\n"); int result = 42; xmlSchemaParserCtxtPtr parserCtxt = NULL; xmlSchemaPtr schema = NULL; xmlSchemaValidCtxtPtr validCtxt = NULL; xmlDocPtr xmlDocumentPointer = xmlParseMemory(xmlSource, xmlLength); parserCtxt = xmlSchemaNewParserCtxt(xsdPath); if (parserCtxt == NULL) { fprintf(stderr, "Could not create XSD schema parsing context.\n"); goto leave; } schema = xmlSchemaParse(parserCtxt); if (schema == NULL) { fprintf(stderr, "Could not parse XSD schema.\n"); goto leave; } validCtxt = xmlSchemaNewValidCtxt(schema); if (!validCtxt) { fprintf(stderr, "Could not create XSD schema validation context.\n"); goto leave; } xmlSetStructuredErrorFunc(NULL, NULL); xmlSetGenericErrorFunc(NULL, handleValidationError); xmlThrDefSetStructuredErrorFunc(NULL, NULL); xmlThrDefSetGenericErrorFunc(NULL, handleValidationError); result = xmlSchemaValidateDoc(validCtxt, xmlDocumentPointer); leave: if (parserCtxt) { xmlSchemaFreeParserCtxt(parserCtxt); } if (schema) { xmlSchemaFree(schema); } if (validCtxt) { xmlSchemaFreeValidCtxt(validCtxt); } printf("\n"); printf("Validation successful: %s (result: %d)\n", (result == 0) ? "YES" : "NO", result); return 0; } console output: XSD File: /Users/dephiniteloop/Desktop/xml_validate/schema.xsd XML File: /Users/dephiniteloop/Desktop/xml_validate/test.gkml XML Source: <?xml version="1.0" encoding="UTF-8"?> <foo xmlns="http://example.com/XMLSchema/1.0"> </foo> Validation Error: Element '{http://example.com/XMLSchema/1.0}foo': No matching global declaration available for the validation root. Validation successful: NO (result: 1845) In case it matters: I'm on OSX 10.6.7 with its default libxml2.dylib (/Developer/SDKs/MacOSX10.6.sdk/usr/lib/libxml2.2.7.3.dylib)

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  • Thread scheduling C

    - by MRP
    include <pthread.h> include <stdio.h> include <stdlib.h> #define NUM_THREADS 4 #define TCOUNT 5 #define COUNT_LIMIT 13 int done = 0; int count = 0; int thread_ids[4] = {0,1,2,3}; int thread_runtime[4] = {0,5,4,1}; pthread_mutex_t count_mutex; pthread_cond_t count_threshold_cv; void *inc_count(void *t) { int i; long my_id = (long)t; long run_time = thread_runtime[my_id]; if (my_id==2 && done ==0) { for(i=0; i< 5 ; i++) { if( i==4 ){done =1;} pthread_mutex_lock(&count_mutex); count++; if (count == COUNT_LIMIT) { pthread_cond_signal(&count_threshold_cv); printf("inc_count(): thread %ld, count = %d Threshold reached.\n", my_id, count); } printf("inc_count(): thread %ld, count = %d, unlocking mutex\n", my_id, count); pthread_mutex_unlock(&count_mutex); } } if (my_id==3 && done==1) { for(i=0; i< 4 ; i++) { if(i == 3 ){ done = 2;} pthread_mutex_lock(&count_mutex); count++; if (count == COUNT_LIMIT) { pthread_cond_signal(&count_threshold_cv); printf("inc_count(): thread %ld, count = %d Threshold reached.\n", my_id, count); } printf("inc_count(): thread %ld, count = %d, unlocking mutex\n", my_id, count); pthread_mutex_unlock(&count_mutex); } } if (my_id==4&& done == 2) { for(i=0; i< 8 ; i++) { pthread_mutex_lock(&count_mutex); count++; if (count == COUNT_LIMIT) { pthread_cond_signal(&count_threshold_cv); printf("inc_count(): thread %ld, count = %d Threshold reached.\n",my_id, count); } printf("inc_count(): thread %ld, count = %d, unlocking mutex\n", my_id, count); pthread_mutex_unlock(&count_mutex); } } pthread_exit(NULL); } void *watch_count(void *t) { long my_id = (long)t; printf("Starting watch_count(): thread %ld\n", my_id); pthread_mutex_lock(&count_mutex); if (count<COUNT_LIMIT) { pthread_cond_wait(&count_threshold_cv, &count_mutex); printf("watch_count(): thread %ld Condition signal received.\n", my_id); count += 125; printf("watch_count(): thread %ld count now = %d.\n", my_id, count); } pthread_mutex_unlock(&count_mutex); pthread_exit(NULL); } int main (int argc, char *argv[]) { int i, rc; long t1=1, t2=2, t3=3, t4=4; pthread_t threads[4]; pthread_attr_t attr; pthread_mutex_init(&count_mutex, NULL); pthread_cond_init (&count_threshold_cv, NULL); pthread_attr_init(&attr); pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_JOINABLE); pthread_create(&threads[0], &attr, watch_count, (void *)t1); pthread_create(&threads[1], &attr, inc_count, (void *)t2); pthread_create(&threads[2], &attr, inc_count, (void *)t3); pthread_create(&threads[3], &attr, inc_count, (void *)t4); for (i=0; i<NUM_THREADS; i++) { pthread_join(threads[i], NULL); } printf ("Main(): Waited on %d threads. Done.\n", NUM_THREADS); pthread_attr_destroy(&attr); pthread_mutex_destroy(&count_mutex); pthread_cond_destroy(&count_threshold_cv); pthread_exit(NULL); } so this code creates 4 threads. thread 1 keeps track of the count value while the other 3 increment the count value. the run time is the number of times the thread will increment the count value. I have a done value that allows the first thread to increment the count value first until its run time is up.. so its like a First Come First Serve. my question is, is there a better way of implementing this? I have read about SCHED_FIFO or SCHED_RR.. I guess I dont know how to implement them into this code or if it can be.

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  • Flex/bison, error: undeclared

    - by Imran
    hallo, i have a problem, the followed program gives back an error, error:: Undeclared(first use in function), why this error appears all tokens are declared, but this error comes, can anyone help me, here are the lex and yac files.thanks lex: %{ int yylinenu= 1; int yycolno= 1; %} %x STR DIGIT [0-9] ALPHA [a-zA-Z] ID {ALPHA}(_?({ALPHA}|{DIGIT}))*_? GROUPED_NUMBER ({DIGIT}{1,3})(\.{DIGIT}{3})* SIMPLE_NUMBER {DIGIT}+ NUMMER {GROUPED_NUMBER}|{SIMPLE_NUMBER} %% <INITIAL>{ [\n] {++yylinenu ; yycolno=1;} [ ]+ {yycolno=yycolno+yyleng;} [\t]+ {yycolno=yycolno+(yyleng*8);} "*" {return MAL;} "+" {return PLUS;} "-" {return MINUS;} "/" {return SLASH;} "(" {return LINKEKLAMMER;} ")" {return RECHTEKLAMMER;} "{" {return LINKEGESCHWEIFTEKLAMMER;} "}" {return RECHTEGESCHEIFTEKLAMMER;} "=" {return GLEICH;} "==" {return GLEICHVERGLEICH;} "!=" {return UNGLEICH;} "<" {return KLEINER;} ">" {return GROSSER;} "<=" {return KLEINERGLEICH;} ">=" {return GROSSERGLEICH;} "while" {return WHILE;} "if" {return IF;} "else" {return ELSE;} "printf" {return PRINTF;} ";" {return SEMIKOLON;} \/\/[^\n]* { ;} {NUMMER} {return NUMBER;} {ID} {return IDENTIFIER;} \" {BEGIN(STR);} . {;} } <STR>{ \n {++yylinenu ;yycolno=1;} ([^\"\\]|"\\t"|"\\n"|"\\r"|"\\b"|"\\\"")+ {return STRING;} \" {BEGIN(INITIAL);} } %% yywrap() { } YACC: %{ #include stdio.h> #include string.h> #include "lex.yy.c" void yyerror(char *err); int error=0,linecnt=1; %} %token IDENTIFIER NUMBER STRING COMMENT PLUS MINUS MAL SLASH LINKEKLAMMER RECHTEKLAMMER LINKEGESCHWEIFTEKLAMMER RECHTEGESCHEIFTEKLAMMER GLEICH GLEICHVERGLEICH UNGLEICH GROSSER KLEINER GROSSERGLEICH KLEINERGLEICH IF ELSE WHILE PRINTF SEMIKOLON %start Stmts %% Stmts : Stmt {puts("\t\tStmts : Stmt");} |Stmt Stmts {puts("\t\tStmts : Stmt Stmts");} ; //NEUE REGEL---------------------------------------------- Stmt : LINKEGESCHWEIFTEKLAMMER Stmts RECHTEGESCHEIFTEKLAMMER {puts("\t\tStmt : '{' Stmts '}'");} |IF LINKEKLAMMER Cond RECHTEKLAMMER Stmt {puts("\t\tStmt : '(' Cond ')' Stmt");} |IF LINKEKLAMMER Cond RECHTEKLAMMER Stmt ELSE Stmt {puts("\t\tStmt : '(' Cond ')' Stmt 'ELSE' Stmt");} |WHILE LINKEKLAMMER Cond RECHTEKLAMMER Stmt {puts("\t\tStmt : 'PRINTF' Expr ';'");} |PRINTF Expr SEMIKOLON {puts("\t\tStmt : 'PRINTF' Expr ';'");} |IDENTIFIER GLEICH Expr SEMIKOLON {puts("\t\tStmt : 'IDENTIFIER' '=' Expr ';'");} |SEMIKOLON {puts("\t\tStmt : ';'");} ;//NEUE REGEL --------------------------------------------- Cond: Expr GLEICHVERGLEICH Expr {puts("\t\tCond : '==' Expr");} |Expr UNGLEICH Expr {puts("\t\tCond : '!=' Expr");} |Expr KLEINER Expr {puts("\t\tCond : '<' Expr");} |Expr KLEINERGLEICH Expr {puts("\t\tCond : '<=' Expr");} |Expr GROSSER Expr {puts("\t\tCond : '>' Expr");} |Expr GROSSERGLEICH Expr {puts("\t\tCond : '>=' Expr");} ;//NEUE REGEL -------------------------------------------- Expr:Term {puts("\t\tExpr : Term");} |Term PLUS Expr {puts("\t\tExpr : Term '+' Expr");} |Term MINUS Expr {puts("\t\tExpr : Term '-' Expr");} ;//NEUE REGEL -------------------------------------------- Term:Factor {puts("\t\tTerm : Factor");} |Factor MAL Term {puts("\t\tTerm : Factor '*' Term");} |Factor SLASH Term {puts("\t\tTerm : Factor '/' Term");} ;//NEUE REGEL -------------------------------------------- Factor:SimpleExpr {puts("\t\tFactor : SimpleExpr");} |MINUS SimpleExpr {puts("\t\tFactor : '-' SimpleExpr");} ;//NEUE REGEL -------------------------------------------- SimpleExpr:LINKEKLAMMER Expr RECHTEKLAMMER {puts("\t\tSimpleExpr : '(' Expr ')'");} |IDENTIFIER {puts("\t\tSimpleExpr : 'IDENTIFIER'");} |NUMBER {puts("\t\tSimpleExpr : 'NUMBER'");} |STRING {puts("\t\tSimpleExpr : 'String'");} ;//ENDE ------------------------------------------------- %% void yyerror(char *msg) { error=1; printf("Line: %d , Column: %d : %s \n", yylinenu, yycolno,yytext, msg); } int main(int argc, char *argv[]) { int val; while(yylex()) { printf("\n",yytext); } return yyparse(); }

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  • Representing robot's elbow angle in 3-D

    - by Onkar Deshpande
    I am given coordinates of two points in 3-D viz. shoulder point and object point(to which I am supposed to reach). I am also given the length from my shoulder-to-elbow arm and the length of my forearm. I am trying to solve for the unknown position(the position of the joint elbow). I am using cosine rule to find out the elbow angle. Here is my code - #include <stdio.h> #include <math.h> #include <stdlib.h> struct point { double x, y, z; }; struct angles { double clock_wise; double counter_clock_wise; }; double max(double a, double b) { return (a > b) ? a : b; } /* * Check if the combination can make a triangle by considering the fact that sum * of any two sides of a triangle is greater than the remaining side. The * overlapping condition of links is handled separately in main(). */ int valid_triangle(struct point p0, double l0, struct point p1, double l1) { double dist = sqrt(pow((fabs(p1.z - p0.z)), 2) + pow((fabs(p1.y - p0.y)), 2) + pow((fabs(p1.x - p0.x)), 2)); if((max(dist, l0) == dist) && max(dist, l1) == dist) { return (dist < (l0 + l1)); } else if((max(dist, l0) == l0) && (max(l0, l1) == l0)) { return (l0 < (dist + l1)); } else { return (l1 < (dist + l0)); } } /* * Cosine rule is used to find the elbow angle. Positive value indicates a * counter clockwise angle while negative value indicates a clockwise angle. * Since this problem has at max 2 solutions for any given position of P0 and * P1, I am returning a structure of angles which can be used to consider angles * from both direction viz. clockwise-negative and counter-clockwise-positive */ void return_config(struct point p0, double l0, struct point p1, double l1, struct angles *a) { double dist = sqrt(pow((fabs(p1.z - p0.z)), 2) + pow((fabs(p1.y - p0.y)), 2) + pow((fabs(p1.x - p0.x)), 2)); double degrees = (double) acos((l0 * l0 + l1 * l1 - dist * dist) / (2 * l0 * l1)) * (180.0f / 3.1415f); a->clock_wise = -degrees; a->counter_clock_wise = degrees; } int main() { struct point p0, p1; struct angles a; p0.x = 15, p0.y = 4, p0.z = 0; p1.x = 20, p1.y = 4, p1.z = 0; double l0 = 5, l1 = 8; if(valid_triangle(p0, l0, p1, l1)) { printf("Three lengths can make a valid configuration \n"); return_config(p0, l0, p1, l1, &a); printf("Angle of the elbow point (clockwise) = %lf, (counter clockwise) = %lf \n", a.clock_wise, a.counter_clock_wise); } else { double dist = sqrt(pow((fabs(p1.z - p0.z)), 2) + pow((fabs(p1.y - p0.y)), 2) + pow((fabs(p1.x - p0.x)), 2)); if((dist <= (l0 + l1)) && (dist > l0)) { a.clock_wise = -180.0f; a.counter_clock_wise = 180.0f; printf("Angle of the elbow point (clockwise) = %lf, (counter clockwise) = %lf \n", a.clock_wise, a.counter_clock_wise); } else if((dist <= fabs(l0 - l1)) && (dist < l0)){ a.clock_wise = -0.0f; a.counter_clock_wise = 0.0f; printf("Angle of the elbow point (clockwise) = %lf, (counter clockwise) = %lf \n", a.clock_wise, a.counter_clock_wise); } else printf("Given combination cannot make a valid configuration\n"); } return 0; } However, this solution makes sense only in 2-D. Because clockwise and counter-clockwise are meaningless without an axis and direction of rotation. Returning only an angle is technically correct but it leaves a lot of work for the client of this function to use the result in meaningful way. How can I make the changes to get the axis and direction of rotation ? Also, I want to know how many possible solution could be there for this problem. Please let me know your thoughts ! Any help is highly appreciated ...

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  • "The usage of semaphores is subtly wrong"

    - by Hoonose
    This past semester I was taking an OS practicum in C, in which the first project involved making a threads package, then writing a multiple producer-consumer program to demonstrate the functionality. However, after getting grading feedback, I lost points for "The usage of semaphores is subtly wrong" and "The program assumes preemption (e.g. uses yield to change control)" (We started with a non-preemptive threads package then added preemption later. Note that the comment and example contradict each other. I believe it doesn't assume either, and would work in both environments). This has been bugging me for a long time - the course staff was kind of overwhelmed, so I couldn't ask them what's wrong with this over the semester. I've spent a long time thinking about this and I can't see the issues. If anyone could take a look and point out the error, or reassure me that there actually isn't a problem, I'd really appreciate it. I believe the syntax should be pretty standard in terms of the thread package functions (minithreads and semaphores), but let me know if anything is confusing. #include <stdio.h> #include <stdlib.h> #include "minithread.h" #include "synch.h" #define BUFFER_SIZE 16 #define MAXCOUNT 100 int buffer[BUFFER_SIZE]; int size, head, tail; int count = 1; int out = 0; int toadd = 0; int toremove = 0; semaphore_t empty; semaphore_t full; semaphore_t count_lock; // Semaphore to keep a lock on the // global variables for maintaining the counts /* Method to handle the working of a student * The ID of a student is the corresponding minithread_id */ int student(int total_burgers) { int n, i; semaphore_P(count_lock); while ((out+toremove) < arg) { n = genintrand(BUFFER_SIZE); n = (n <= total_burgers - (out + toremove)) ? n : total_burgers - (out + toremove); printf("Student %d wants to get %d burgers ...\n", minithread_id(), n); toremove += n; semaphore_V(count_lock); for (i=0; i<n; i++) { semaphore_P(empty); out = buffer[tail]; printf("Student %d is taking burger %d.\n", minithread_id(), out); tail = (tail + 1) % BUFFER_SIZE; size--; toremove--; semaphore_V(full); } semaphore_P(count_lock); } semaphore_V(count_lock); printf("Student %d is done.\n", minithread_id()); return 0; } /* Method to handle the working of a cook * The ID of a cook is the corresponding minithread_id */ int cook(int total_burgers) { int n, i; printf("Creating Cook %d\n",minithread_id()); semaphore_P(count_lock); while ((count+toadd) <= arg) { n = genintrand(BUFFER_SIZE); n = (n <= total_burgers - (count + toadd) + 1) ? n : total_burgers - (count + toadd) + 1; printf("Cook %d wants to put %d burgers into the burger stack ...\n", minithread_id(),n); toadd += n; semaphore_V(count_lock); for (i=0; i<n; i++) { semaphore_P(full); printf("Cook %d is putting burger %d into the burger stack.\n", minithread_id(), count); buffer[head] = count++; head = (head + 1) % BUFFER_SIZE; size++; toadd--; semaphore_V(empty); } semaphore_P(count_lock); } semaphore_V(count_lock); printf("Cook %d is done.\n", minithread_id()); return 0; } /* Method to create our multiple producers and consumers * and start their respective threads by fork */ void starter(int* c){ int i; for (i=0;i<c[2];i++){ minithread_fork(cook, c[0]); } for (i=0;i<c[1];i++){ minithread_fork(student, c[0]); } } /* The arguments are passed as command line parameters * argv[1] is the no of students * argv[2] is the no of cooks */ void main(int argc, char *argv[]) { int pass_args[3]; pass_args[0] = MAXCOUNT; pass_args[1] = atoi(argv[1]); pass_args[2] = atoi(argv[2]); size = head = tail = 0; empty = semaphore_create(); semaphore_initialize(empty, 0); full = semaphore_create(); semaphore_initialize(full, BUFFER_SIZE); count_lock = semaphore_create(); semaphore_initialize(count_lock, 1); minithread_system_initialize(starter, pass_args); }

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