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Search found 916 results on 37 pages for 'stdio'.

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  • Segmentation Fault

    - by Biranchi
    Hi All, I have the following piece of code for getting the hostname and IP address, #include <stdlib.h> #include <stdio.h> #include <netdb.h> /* This is the header file needed for gethostbyname() */ #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> int main(int argc, char *argv[]) { struct hostent *he; if (argc!=2){ printf("Usage: %s <hostname>\n",argv[0]); exit(-1); } if ((he=gethostbyname(argv[1]))==NULL){ printf("gethostbyname() error\n"); exit(-1); } printf("Hostname : %s\n",he->h_name); /* prints the hostname */ printf("IP Address: %s\n",inet_ntoa(*((struct in_addr *)he->h_addr))); /* prints IP address */ } but i am getting a warning and segmentation fault as host.c: In function ‘main’: host.c:24: warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘int’ What is the error in the code ?? Thanks

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  • Pascals Triangle by recursion

    - by Olpers
    Note : My Class Teacher gave me this question as an assignment... I am not asked to do it but please tell me how to do it with recursion Binomial coefficients can be calculated using Pascal's triangle: 1 n = 0 1 1 1 2 1 1 3 3 1 1 4 6 4 1 n = 4 Each new level of the triangle has 1's on the ends; the interior numbers are the sums of the two numbers above them. Task: Write a program that includes a recursive function to produce a list of binomial coefficients for the power n using the Pascal's triangle technique. For example, Input = 2 Output = 1 2 1 Input = 4 Output = 1 4 6 4 1 done this So Far but tell me how to do this with recursion... #include<stdio.h> int main() { int length,i,j,k; //Accepting length from user printf("Enter the length of pascal's triangle : "); scanf("%d",&length); //Printing the pascal's triangle for(i=1;i<=length;i++) { for(j=1;j<=length-i;j++) printf(" "); for(k=1;k<i;k++) printf("%d",k); for(k=i;k>=1;k--) printf("%d",k); printf("\n"); } return 0; }

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  • How to access variables in shared memory

    - by user1723361
    I am trying to create a shared memory segment containing three integers and an array. The segment is created and a pointer is attached, but when I try to access the values of the variables (whether changing, printing, etc.) I get a segmentation fault. Here is the code I tried: #include <stdio.h> #include <stdbool.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h> #define SIZE 10 int* shm_front; int* shm_end; int* shm_count; int* shm_array; int shm_size = 3*sizeof(int) + sizeof(shm_array[SIZE]); int main(int argc, char* argsv[]) { int shmid; //create shared memory segment if((shmid = shmget(IPC_PRIVATE, shm_size, 0644)) == -1) { printf("error in shmget"); exit(1); } //obtain the pointer to the segment if((shm_front = (int*)shmat(shmid, (void *)0, 0)) == (void *)-1) { printf("error in shmat"); exit(1); } //move down the segment to set the other pointers shm_end = shm_front + 1; shm_count = shm_front + 2; shm_array = shm_front + 3; //tests on shm //*shm_end = 10; //gives segmentation fault //printf("\n%d", *shm_front); //gives segmentation fault //clean-up //get rid of shared memory shmdt(shm_front); shmctl(shmid, IPC_RMID, NULL); //printf("\n\n"); return 0; } I tried accessing the shared memory by dereferencing the pointer to the struct, but got a segmentation fault each time.

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  • Python ctypes in_dll string assignment

    - by ackdesha
    I could use some help assigning to a global C variable in DLL using ctypes. The following is an example of what I'm trying: test.c contains the following #include <stdio.h> char name[60]; void test(void) { printf("Name is %s\n", name); } On windows (cygwin) I build a DLL (Test.dll) as follows: gcc -g -c -Wall test.c gcc -Wall -mrtd -mno-cygwin -shared -W1,--add-stdcall-alias -o Test.dll test.o When trying to modify the name variable and then calling the C test function using the ctypes interface I get the following... >>> from ctypes import * >>> dll = windll.Test >>> dll <WinDLL 'Test', handle ... at ...> >>> f = c_char_p.in_dll(dll, 'name') >>> f c_char_p(None) >>> f.value = 'foo' >>> f c_char_p('foo') >>> dll.test() Name is Name is 48+? 13 Why does the test function print garbage in this case?

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  • C program - Seg fault, cause of

    - by resonant_fractal
    Running this gives me a seg fault (gcc filename.c -lm), when i enter 6 (int) as a value. Please help me get my head around this. The intended functionality has not yet been implemented, but I need to know why I'm headed into seg faults already. Thanks! #include<stdio.h> #include<math.h> int main (void) { int l = 5; int n, i, tmp, index; char * s[] = {"Sheldon", "Leonard", "Penny", "Raj", "Howard"}; scanf("%d", &n); //Solve Sigma(Ai*2^(i-1)) = (n - k)/l if (n/l <= 1) printf("%s\n", s[n-1]); else { tmp = n; for (i = 1;;) { tmp = tmp - (l * pow(2,i-1)); if (tmp <= 5) { // printf("Breaking\n"); break; } ++i; } printf("Last index = %d\n", i); // ***NOTE*** //Value lies in next array, therefore ++i; index = tmp + pow(2, n-1); printf("%d\n", index); } return 0; }

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  • how to write binary copy of structure array to file

    - by cerr
    I would like to write a binary image of a structure array to a binary file. I have tried this so far: #include <stdio.h> #include <string.h> #define NUM 256 const char *fname="binary.bin"; typedef struct foo_s { int intA; int intB; char string[20]; }foo_t; void main (void) { foo_t bar[NUM]; bar[0].intA = 10; bar[0].intB = 999; strcpy(bar[0].string,"Hello World!"); Save(bar); printf("%s written succesfully!\n",fname); } int Save(foo_t* pData) { FILE *pFile; int ptr = 0; int itr = 0; pFile = fopen(fname, "w"); if (pFile == NULL) { printf("couldn't open %s\n", fname); return; } for (itr = 0; itr<NUM; itr++) { for (ptr=0; ptr<sizeof(foo_t); ptr++) { fputc((unsigned char)*((&pData[itr])+ptr), pFile); } fclose(pFile); } } but the compiler is saying aggregate value used where an integer was expected fputc((unsigned char)*((&pData[itr])+ptr), pFile); and I don't quite understand why, what am I doing wrong? Thanks!

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  • returning a pointed to an object within a std::vector

    - by memC
    I have a very basic question on returning a reference to an element of a vector . There is a vector vec that stores instances of class Foo. I want to access an element from this vector . ( don't want to use the vector index) . How should I code the method getFoo here? #include<vector> #include<stdio.h> #include<iostream> #include<math.h> using namespace std; class Foo { public: Foo(){}; ~Foo(){}; }; class B { public: vector<Foo> vec; Foo* getFoo(); B(){}; ~B(){}; }; Foo* B::getFoo(){ int i; vec.push_back(Foo()); i = vec.size() - 1; // how to return a pointer to vec[i] ?? return vec.at(i); }; int main(){ B b; b = B(); int i = 0; for (i = 0; i < 5; i ++){ b.getFoo(); } return 0; }

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  • Question on passing a pointer to a structure in C to a function?

    - by worlds-apart89
    Below, I wrote a primitive singly linked list in C. Function "addEditNode" MUST receive a pointer by value, which, I am guessing, means we can edit the data of the pointer but can not point it to something else. If I allocate memory using malloc in "addEditNode", when the function returns, can I see the contents of first-next ? Second question is do I have to free first-next or is it only first that I should free? I am running into segmentation faults on Linux. #include <stdio.h> #include <stdlib.h> typedef struct list_node list_node_t; struct list_node { int value; list_node_t *next; }; void addEditNode(list_node_t *node) { node->value = 10; node->next = (list_node_t*) malloc(sizeof(list_node_t)); node->next->value = 1; node->next->next = NULL; } int main() { list_node_t *first = (list_node_t*) malloc(sizeof(list_node_t)); first->value = 1; first->next = NULL; addEditNode(first); free(first); return 0; }

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  • Can the size of a structure change after compiled?

    - by Sarah Altiva
    Hi, suppose you have the following structure: #include <windows.h> // BOOL is here. #include <stdio.h> typedef struct { BOOL someBool; char someCharArray[100]; int someIntValue; BOOL moreBools, anotherOne, yetAgain; char someOthercharArray[23]; int otherInt; } Test; int main(void) { printf("Structure size: %d, BOOL size: %d.\n", sizeof(Test), sizeof(BOOL)); } When I compile this piece of code in my machine (32-bit OS) the output is the following: Structure size: 148, BOOL size: 4. I would like to know if, once compiled, these values may change depending on the machine which runs the program. E.g.: if I ran this program in a 64-bit machine, would the output be the same? Or once it's compiled it'll always be the same? Thank you very much, and forgive me if the answer to this question is obvious...

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  • C Typecast: How to

    - by Jean
    #include<stdio.h> int main(void) { unsigned short a,e,f ; // 2 bytes data type unsigned int temp1,temp2,temp4; // 4 bytes data type unsigned long temp3; // 8 bytes data type a=0xFFFF; e=((a*a)+(a*a))/(2*a); // Line 8 //e=(((unsigned long)(a*a)+(unsigned long)(a*a)))/(unsigned int)(2*a); temp1=a*a; temp2=a*a; temp3=(unsigned long)temp1+(unsigned long)temp2; // Line 14 temp4=2*a; f=temp3/temp4; printf("%u,%u,%lu,%u,%u,%u,%u\n",temp1,temp2,temp3,temp4,e,f,a); return(1); } How do I fix the arithmetic (At Line 8 by appropriate typecasting of intermediate results) so that overflows are taken care of ? Currently it prints 65534 instead of expected 65535. Why is the typecast necessary for Line 14 ?

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  • complete nub.. iostream file not found

    - by user1742389
    folks I am almost completely new to programming so please bear with me. I am using the first example from lydia.com c++ videos and failing. I am using Xcode 4.5.1 with a c++ command line project instead of eclipse and I am getting an error on compile of iostream file not found. the code is simple and I will include exactly what I have at the end of this message. I thought that iostream was a standard header that came with all even remotely recent versions of c++ compilers and am shocked to get this error and I cannot find any way to fix this. please tell me whats going on. #include <iostream> #include <stdio.h> #include <sstream> #include <vector> int main(int argc, char ** argv) { stringstream version; version << "GCC Version"; _GNUC_<<"."<<_GNUC_MINOR_<<"."<<_GNUC_PATCHLEVEL_<<_"\nVersion String: " <<_VERSION_; cout <<version.string() endl; vector<string> v={"one","two","three"}; for ( s : v ) { cout << s <<endl; } // insert code here... printf("Hello, World!\n"); return 0; } Thanks.

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  • pointer to a pointer in a linked list

    - by user1596497
    I'm trying to set a linked list head through pointer to a pointer. I can see inside the function that the address of the head pointer is changing but as i return to the main progran it becomes NULL again. can someone tell me what I'm doing wrong ?? #include <stdio.h> #include <stdlib.h> typedef void(*fun_t)(int); typedef struct timer_t { int time; fun_t func; struct timer_t *next; }TIMER_T; void add_timer(int sec, fun_t func, TIMER_T *head); void run_timers(TIMER_T **head); void timer_func(int); int main(void) { TIMER_T *head = NULL; int time = 1; fun_t func = timer_func; while (time < 1000) { printf("\nCalling add_timer(time=%d, func=0x%x, head=0x%x)\n", time, func, &head); add_timer(time, func, head); time *= 2; } run_timers(&head); return 0; } void add_timer(int sec, fun_t func, TIMER_T *head) { TIMER_T ** ppScan=&head; TIMER_T *new_timer = NULL; new_timer = (TIMER_T*)malloc(sizeof(TIMER_T)); new_timer->time = sec; new_timer->func = func; new_timer->next = NULL; while((*ppScan != NULL) && (((**ppScan).time)<sec)) ppScan = &(*ppScan)->next; new_timer->next = *ppScan; *ppScan = new_timer; }

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  • Why does mmap() fail with ENOMEM on a 1TB sparse file?

    - by metadaddy
    I've been working with large sparse files on openSUSE 11.2 x86_64. When I try to mmap() a 1TB sparse file, it fails with ENOMEM. I would have thought that the 64 bit address space would be adequate to map in a terabyte, but it seems not. Experimenting further, a 1GB file works fine, but a 2GB file (and anything bigger) fails. I'm guessing there might be a setting somewhere to tweak, but an extensive search turns up nothing. Here's some sample code that shows the problem - any clues? #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/mman.h> #include <sys/types.h> #include <unistd.h> int main(int argc, char *argv[]) { char * filename = argv[1]; int fd; off_t size = 1UL << 40; // 30 == 1GB, 40 == 1TB fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0666); ftruncate(fd, size); printf("Created %ld byte sparse file\n", size); char * buffer = (char *)mmap(NULL, (size_t)size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); if ( buffer == MAP_FAILED ) { perror("mmap"); exit(1); } printf("Done mmap - returned 0x0%lx\n", (unsigned long)buffer); strcpy( buffer, "cafebabe" ); printf("Wrote to start\n"); strcpy( buffer + (size - 9), "deadbeef" ); printf("Wrote to end\n"); if ( munmap(buffer, (size_t)size) < 0 ) { perror("munmap"); exit(1); } close(fd); return 0; }

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  • I can't compile this code

    - by heshim
    #include <stdio.h> #define IN 1 /* inside a word */ #define OUT 0 /* outside a word */ /* count lines, words, and characters in input */ main() { int c, nl, nw, nc, state; state = OUT; nl = nw = nc = 0; while ((c = getchar()) != EOF) { ++nc; if (c == '\n') ++nl; if (c == ' ' || c == '\n' || c = '\t') state = OUT; else if (state == OUT) { state = IN; ++nw; } } printf("%d %d %d\n", nl, nw, nc); } I got K&R book but there are some codes that don't compile ! it gives me - 19 C:\Users\Nom\Desktop\Untitled1.c invalid lvalue in assignment edit: now it works, thanks guys, but now it does nothing ! the printf statement doesn't work. It opens the dos console, I type anything and it just return a new line. I'm using Dev-C++ 4.9.9.2 I put the printf statement inside the while loop and it works now. thanks

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  • Externally disabling signals for a Linux program.

    - by Harry
    Hello, On Linux, is it possible to somehow disable signaling for programs externally... that is, without modifying their source code? Context: I'm calling a C (and also a Java) program from within a bash script on Linux. I don't want any interruptions for my bash script, and for the other programs that the script launches (as foreground processes). While I can use a... trap '' INT ... in my bash script to disable the Ctrl C signal, this works only when the program control happens to be in the bash code. That is, if I press Ctrl C while the C program is running, the C program gets interrupted and it exits! This C program is doing some critical operation because of which I don't want it be interrupted. I don't have access to the source code of this C program, so signal handling inside the C program is out of question. #!/bin/bash trap 'echo You pressed Ctrl C' INT # A C program to emulate a real-world, long-running program, # which I don't want to be interrupted, and for which I # don't have the source code! # # File: y.c # To build: gcc -o y y.c # # #include <stdio.h> # int main(int argc, char *argv[]) { # printf("Performing a critical operation...\n"); # for(;;); // Do nothing forever. # printf("Performing a critical operation... done.\n"); # } ./y Regards, /HS

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  • throwing exception from APCProc crashes program

    - by lazy_banana
    I started to do some research on how terminate a multithreaded application properly and I found those 2 post(first, second) about how to use QueueUserAPC to signal other threads to terminate. I thought I should give it a try, and the application keeps crashing when I throw the exception from the APCProc. Code: #include <stdio.h> #include <windows.h> class ExitException { public: char *desc; DWORD exit_code; ExitException(char *desc,int exit_code): desc(desc), exit_code(exit_code) {} }; //I use this class to check if objects are deconstructed upon termination class Test { public: char *s; Test(char *s): s(s) { printf("%s ctor\n",s); } ~Test() { printf("%s dctor\n",s); } }; DWORD CALLBACK ThreadProc(void *useless) { try { Test t("thread_test"); SleepEx(INFINITE,true); return 0; } catch (ExitException &e) { printf("Thread exits\n%s %lu",e.desc,e.exit_code); return e.exit_code; } } void CALLBACK exit_apc_proc(ULONG_PTR param) { puts("In APCProc"); ExitException e("Application exit signal!",1); throw e; return; } int main() { HANDLE thread=CreateThread(NULL,0,ThreadProc,NULL,0,NULL); Sleep(1000); QueueUserAPC(exit_apc_proc,thread,0); WaitForSingleObject(thread,INFINITE); puts("main: bye"); return 0; } My question is why does this happen? I use mingw for compilation and my OS is 64bit. Can this be the reason?I read that you shouldn't call QueueApcProc from a 32bit app for a thread which runs in a 64bit process or vice versa, but this shouldn't be the case.

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  • Porting Perl to C++ `print "\x{2501}" x 12;`

    - by jippie
    I am porting a program from Perl to C++ as a learning objective. I arrived at a routine that draws a table with commands like the following: Perl: print "\x{2501}" x 12; And it draws 12 times a '?' ("box drawings heavy horizontal"). Now I figured out part of the problem already: Perl: \x{}, \x00 Hexadecimal escape sequence; C++: \unnnn To print a single Unicode character: C++: printf( "\u250f\n" ); But does C++ have a smart equivalent for the 'x' operator or would it come down to a for loop? UPDATE Let me include the full source code I am trying to compile with the proposed solution. The compiler does throw an errors: g++ -Wall -Werror project.cpp -o project project.cpp: In function ‘int main(int, char**)’: project.cpp:38:3: error: ‘string’ is not a member of ‘std’ project.cpp:38:15: error: expected ‘;’ before ‘s’ project.cpp:39:3: error: ‘cout’ is not a member of ‘std’ project.cpp:39:16: error: ‘s’ was not declared in this scope #include <stdlib.h> #include <stdint.h> #include <stdio.h> #include <string.h> int main ( int argc, char *argv[] ) { if ( argc != 2 ) { fprintf( stderr , "usage: %s matrix\n", argv[0] ); exit( 2 ); } else { //std::string s(12, "\u250f" ); std::string s(12, "u" ); std::cout << s; } }

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  • basic file input using C

    - by user1781966
    So im working on learning how to do file I/O, but the book I'm using is terrible at teaching how to receive input from a file. Below is is their example of how to receive input from a file, but it doesn't work. I have copied it word for word, and it should loop through a list of names until it reaches the end of the file( or so they say in the book), but it doesn't. In fact if I leave the while loop in there, it doesn't print anything. #include <stdio.h> #include <conio.h> int main() { char name[10]; FILE*pRead; pRead=fopen("test.txt", "r"); if (pRead==NULL) { printf("file cannot be opened"); }else printf("contents of test.txt"); fscanf(pRead,"%s",name); while(!feof(pRead)) { printf("%s\n",name); fscanf(pRead, "%s", name); } getch(); } Even online, every beginners tutorial I see does some variation of this, but I can't seem to get it to work even a little bit.

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  • Simulation tree command in C

    - by Ecle
    I have to create the simulation of tree command in C, this is my current code: #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <dirent.h> #include <string.h> main(int argc, char *argv[]){ int i; if(argc < 2){ printf("\nError. Use: %s directory\n", argv[0]); system("exit"); } for(i=1;i<argc;i++) //if(argv[i][0] != '-') tree(argv[i]); } tree(char *ruta){ DIR *dirp; struct dirent *dp; static nivel = 0; struct stat buf; char fichero[256]; int i; if((dirp = opendir(path)) == NULL){ perror(path); return; } while((dp = readdir(dirp)) != NULL){ printf(fichero, "%s/%s", path, dp->d_name); if((buf.st_mode & S_IFMT) == S_IFDIR){ for(i=0;i<nivel;i++) printf("\t"); printf("%s\n", dp->d_name); ++nivel; tree(fichero); --nivel; } } } Apparently, it works! (due to it compiles correctly) But I don't why. I can't pass the correct arguments to execute this. Thank you so much, people.

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  • Store a signed long int (32bit) as 4 octets?

    - by Doori Bar
    I managed to get a unsigned long int octets-representation (BE) by reading IPv4 methods, and I managed to read about how signed integers are using the MSB as the sign indicator, which makes 00 00 00 00 to be 0, while 7F FF FF FF is 2147483647. But I can't manage how to do the same for signed long integers? #include <stdio.h> #include <string.h> int main (void) { unsigned long int intu32; unsigned char octets[4]; intu32 = 255; octets[3] = (intu32) & 255; octets[2] = (intu32 >> 8) & 255; octets[1] = (intu32 >> 16) & 255; octets[0] = (intu32 >> 24) & 255; printf("(%d)(%d)(%d)(%d)\n", octets[0], octets[1], octets[2], octets[3]); intu32 = (octets[0] << 24) | (octets[1] << 16) | (octets[2] << 8) | octets[3]; printf("intu32:%lu\n", intu32); return 0; } Thanks in advance, Doori bar

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  • Pointer and malloc issue

    - by Andy
    I am fairly new to C and am getting stuck with arrays and pointers when they refer to strings. I can ask for input of 2 numbers (ints) and then return the one I want (first number or second number) without any issues. But when I request names and try to return them, the program crashes after I enter the first name and not sure why. In theory I am looking to reserve memory for the first name, and then expand it to include a second name. Can anyone explain why this breaks? Thanks! #include <stdio.h> #include <stdlib.h> void main () { int NumItems = 0; NumItems += 1; char* NameList = malloc(sizeof(char[10])*NumItems); printf("Please enter name #1: \n"); scanf("%9s", NameList[0]); fpurge(stdin); NumItems += 1; NameList = realloc(NameList,sizeof(char[10])*NumItems); printf("Please enter name #2: \n"); scanf("%9s", NameList[1]); fpurge(stdin); printf("The first name is: %s",NameList[0]); printf("The second name is: %s",NameList[1]); return 0; }

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  • C Static Function Confusion

    - by Lime
    I am trying to make the s_cord_print function visible in the cord_s.c file only. Currently the function is visible/runnable in main.c even when it is declared static. How do I make the s_cord_print function private to cord_s.c? Thanks! s_cord.c typedef struct s_cord{ int x; int y; struct s_cord (*print)(); } s_cord; void* VOID_THIS; #define $(EL) VOID_THIS=&EL;EL static s_cord s_cord_print(){ struct s_cord *THIS; THIS = VOID_THIS; printf("(%d,%d)\n",THIS->x,THIS->y); return *THIS; } const s_cord s_cord_default = {1,2,s_cord_print}; main.c #include <stdio.h> #include <stdlib.h> #include "s_cord.c" int main(){ s_cord mycord = s_cord_default; mycord.x = 2; mycord.y = 3; $(mycord).print().print(); //static didn't seem to hide the function s_cord_print(); return 0; } ~

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  • Functions and arrays

    - by Ordo
    Hello! My little program below shall take 5 numbers from the user, store them into an array of integers and use a function to print them out. Sincerly it doesn't work and nothing is printed out. I can't find a mistake, so i would be glad about any advice. Thanks. #include <stdio.h> void printarray(int intarray[], int n) { int i; for(i = 0; i < n; i ++) { printf("%d", intarray[i]); } } int main () { const int n = 5; int temp = 0; int i; int intarray [n]; char check; printf("Please type in your numbers!\n"); for(i = 0; i < n; i ++) { printf(""); scanf("%d", &temp); intarray[i] = temp; } printf("Do you want to print them out? (yes/no): "); scanf("%c", &check); if (check == 'y') printarray(intarray, n); getchar(); getchar(); getchar(); getchar(); return 0; }

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  • replacing elements horizontally and vertically in a 2D array

    - by wello horld
    the code below ask for the user's input for the 2D array size and prints out something like this: (say an 18x6 grid) .................. .................. .................. .................. .................. .................. code starts here: #include <stdio.h> #define MAX 10 int main() { char grid[MAX][MAX]; int i,j,row,col; printf("Please enter your grid size: "); scanf("%d %d", &row, &col); for (i = 0; i < row; i++) { for (j = 0; j < col; j++) { grid[i][j] = '.'; printf("%c ", grid[i][j]); } printf("\n"); } return 0; } I now ask the user for a string, then ask them where to put it for example: Please enter grid size: 18 6 Please enter word: Hello Please enter location: 0 0 Output: Hello............. .................. .................. .................. .................. .................. Please enter location: 3 4 Output: .................. .................. .................. ..Hello........... .................. .................. program just keeps going. Any thoughts on how to modify the code for this? PS: Vertical seems way hard, but I want to start on horizontal first to have something to work on.

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  • C macro issue: redefinition of functions / structure

    - by Andrei Ciobanu
    Given the following code (it's a macro that generates code for a list data structure, based on the contained type). list.h #ifndef _LIST_H #define _LIST_H #ifdef __cplusplus extern "C" { #endif #define LIST_TEMPLATE_INIT(type) \ typedef struct __list_s_##type { \ struct __list_s_##type *next; \ type value; \ } __list_##type; \ \ __list_##type * __list_##type##_malloc(type value){ \ __list_##type * list = NULL; \ list = malloc(sizeof(*list)); \ list->value = value; \ return list; \ }\ \ void __list_##type##_free(__list_##type *list){\ __list_##type * back = list;\ while(list=list->next){\ free(back);\ back = list;\ }\ } #define LIST_TYPE(type) __list_##type #define LIST_MALLOC(type,value) __list_##type##_malloc(value) #define LIST_FREE(type,list) __list_##type##_free(list) #define LIST_DATA(list) (list->value) #ifdef __cplusplus } #endif #endif /* _LIST_H */ And here is how the above code works: #include <stdio.h> #include <stdlib.h> #include "list.h" /* * */ LIST_TEMPLATE_INIT(int) int main(int argc, char** argv) { LIST_TYPE(int)* list = NULL; list = LIST_MALLOC(int, 5); printf("%d",LIST_DATA(list)); LIST_FREE(int,list); return (0); } My question, is it possible to somehow be able to call : LIST_TEMPLATE_INIT(int), as many times as I want, in a decentralized fashion ? The current issue with this right now is that calling LIST_TEMPLATE_INIT(int) in another file raise compilation errors (because of function redefinition): Example of error: error: redefinition of ‘struct __list_s_int’

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