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  • How to generate GIR files from the Vala compiler?

    - by celil
    I am trying to create python bindings to a vala library using pygi with gobject introspection. However, I am having trouble generating the GIR files (that I am planning to compile to typelib files subsequently). According to the documentation valac should support generating GIR files. Compiling the following helloworld.vala public struct Point { public double x; public double y; } public class Person { public int age = 32; public Person(int age) { this.age = age; } } public int main() { var p = Point() { x=0.0, y=0.1 }; stdout.printf("%f %f\n", p.x, p.y); var per = new Person(22); stdout.printf("%d\n", per.age); return 0; } with the command valac helloworld.vala --gir=Hello-1.0.gir doesn't create the Hello-1.0.gir file as one would expect. How can I generate the gir file?

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  • How is a new programming language actually formed/created ?

    - by hory.incpp
    Fortran-Algol-Cpl-Bcpl-C-C++-Java ..... Seems like every language is built upon an ancestor language. My question : New languages extend parent ones or there is some kind of a trick? e.g. System.out.print() in Java ; is it actually printf() in C, and so on (printf is actually .. in Cpl)? If so, doesn't this make every further language be slower and need more memory? What separates a new language from a framework?

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  • Why doesn't GCC produce a warning when assigning a signed literal to an unsigned type?

    - by maerics
    Several questions on this website reveal pitfalls when mixing signed and unsigned types and most compilers seem to do a good job about generating warnings of this type. However, GCC doesn't seem to care when assigning a signed constant to an unsigned type! Consider the following program: /* foo.c */ #include <stdio.h> int main(void) { unsigned int x=20, y=-30; if (x > y) { printf("%d > %d\n", x, y); } else { printf("%d <= %d\n", x, y); } return 0; } Compilation with GCC 4.2.1 as below produces no output on the console: gcc -Werror -Wall -Wextra -pedantic foo.c -o foo The resulting executable generates the following output: $ ./foo 20 <= -30 Is there some reason that GCC doesn't generate any warning or error message when assigning the signed value -30 to the unsigned integer variable y?

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  • pthread and recursively calling execvp in C

    - by eduke
    To begin I'm sorry for my english :) I looking for a way to create a thread each time my program finds a directory, in order to call the program itself but with a new argv[2] argument (which is the current dir). I did it successfully with fork() but with pthread I've some difficulties. I don't know if I can do something like that : #include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #include <sys/types.h> #include <sys/stat.h> #include <sys/wait.h> #include <dirent.h> int main(int argc, char **argv) { pthread_t threadID[10] = {0}; DIR * dir; struct dirent * entry; struct stat status; pthread_attr_t attr; pthread_attr_init(&attr); int i = 0; char *res; char *tmp; char *file; if(argc != 3) { printf("Usage : %s <file> <dir>\n", argv[0]); exit(EXIT_FAILURE); } if(stat(argv[2],&status) == 0) { dir = opendir(argv[2]); file = argv[1]; } else exit(EXIT_FAILURE); while ((entry = readdir(dir))) { if (strcmp(entry->d_name, ".") && strcmp(entry->d_name, "..")) { tmp = malloc(strlen(argv[2]) + strlen(entry->d_name) + 2); strcpy(tmp, argv[2]); strcat(tmp, "/"); strcat(tmp, entry->d_name); stat(tmp, &status); if (S_ISDIR(status.st_mode)) { argv[2] = tmp; pthread_create( &threadID[i], &attr, execvp(argv[0], argv), NULL); printf("New thread created : %d", i); i++; } else if (!strcmp(entry->d_name, file)) { printf(" %s was found - Thread number = %d\n",tmp, i); break; } free(tmp); } } pthread_join( threadID[i] , &res ); exit(EXIT_SUCCESS); } Actually it doesn't works : pthread_create( &threadID[i], &attr, execvp(argv[0], argv), NULL); I have no runtime error, but when the file to find is in another directory, the thread is not created and so execvp(argv[0], argv) is not called... Thank you for you help, Simon

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  • Using sizeof operator on a typedef-ed struct

    - by sskanitk
    This might be something too obvious. However, I couldn't find the specific answer though many stackoverflow threads talk about different aspects of this. typedef struct _tmp { unsigned int a; unsigned int b; } tmp; int main() { int c=10; if (c <= sizeof tmp) { printf("less\n"); } else { printf("more\n"); } return 0; } I compile this prog as - g++ -lstdc++ a.cpp I get an error - expected primary-expression before ‘)’ token I think I am missing something very obvious and straightforward. But can't seem to pinpoint it :-/ Thanks!

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  • Multiplying char and int together in C part 2

    - by teehoo
    If I do the following: int c0 = CHAR_MAX; //8 bit int c1 = CHAR_MAX; //8-bit int i = c0*c1; //store in 32-bit variable printf("%d\n", i); //prints 16129 We can see that there is no problem with to 8-bit numbers being multiplied together, and producing a 32-bit output. However, if I do int i0 = INT_MAX; //32-bit int i1 = INT_MAX; //32 bit variable long long int ll = i0*i1; //store in 64-bit variable printf("%lld\n", ll); //prints 1..overflow!! In this case, two 32-bit variables were multiplied together, overflowed, and then were assigned to the 64-bit variable. So why did this overflow happen when multiplying the ints, but not the chars? Is it dependent on the default word-size of my machine? (32-bits)

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  • Checking status after wait()

    - by Helper Method
    After creating a child process and exiting it immediately (_exit()), I want to perform a wait and check the status. Now I wonder if in the 'else' branch of the if/else construct I also need to check for WIFSIGNALED. As far as I understand, if I perform a wait, a) an error could have occured (-1), the child could have terminated normally by an (exit() or _exit()), or it could have been terminated by a signal, so the check could be omitted, right? //remainder omitted int status; pid_t t_pid = wait(&status); if (t_pid == -1) { perror("wait"); exit(EXIT_FAILURE); } if (WIFEXITED(status)) { printf("child terminated normally, status = %d\n", WEXITSTATUS(status) ); } else { // <-- do it have to check for WIFSIGNALED() here? printf("child was terminated by a signal, signum = %d\n", WTERMSIG(status) ); }

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  • Implementing callback functions in C

    - by robertjohn123
    Hi, I am a newbie to C.I am trying to implement callback function using function pointers. I am getting an error :test_callback.c:10: error: expected identifier or ‘(’ before ‘void’ when I try to compile the following program: #include<stdio.h> void (*callback) (void); void callback_proc () { printf ("Inside callback funtion\n"); } void register ((void (*callback) (void))) { printf ("Inside registration \n"); callback (); /* Calling an initial callback with function pointer */ } int main () { callback = callback_proc;/* Assigning function to the function pointer */ register (callback);/* Passing the function pointer */ return 0; } What is this error?Can anyone help?

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  • Dynamically register constructor methods in an AbstractFactory at compile time using C++ templates

    - by Horacio
    When implementing a MessageFactory class to instatiate Message objects I used something like: class MessageFactory { public: static Message *create(int type) { switch(type) { case PING_MSG: return new PingMessage(); case PONG_MSG: return new PongMessage(); .... } } This works ok but every time I add a new message I have to add a new XXX_MSG and modify the switch statement. After some research I found a way to dynamically update the MessageFactory at compile time so I can add as many messages as I want without need to modify the MessageFactory itself. This allows for cleaner and easier to maintain code as I do not need to modify three different places to add/remove message classes: #include <stdio.h> #include <stdlib.h> #include <string.h> #include <inttypes.h> class Message { protected: inline Message() {}; public: inline virtual ~Message() { } inline int getMessageType() const { return m_type; } virtual void say() = 0; protected: uint16_t m_type; }; template<int TYPE, typename IMPL> class MessageTmpl: public Message { enum { _MESSAGE_ID = TYPE }; public: static Message* Create() { return new IMPL(); } static const uint16_t MESSAGE_ID; // for registration protected: MessageTmpl() { m_type = MESSAGE_ID; } //use parameter to instanciate template }; typedef Message* (*t_pfFactory)(); class MessageFactory· { public: static uint16_t Register(uint16_t msgid, t_pfFactory factoryMethod) { printf("Registering constructor for msg id %d\n", msgid); m_List[msgid] = factoryMethod; return msgid; } static Message *Create(uint16_t msgid) { return m_List[msgid](); } static t_pfFactory m_List[65536]; }; template <int TYPE, typename IMPL> const uint16_t MessageTmpl<TYPE, IMPL >::MESSAGE_ID = MessageFactory::Register( MessageTmpl<TYPE, IMPL >::_MESSAGE_ID, &MessageTmpl<TYPE, IMPL >::Create); class PingMessage: public MessageTmpl < 10, PingMessage > {· public: PingMessage() {} virtual void say() { printf("Ping\n"); } }; class PongMessage: public MessageTmpl < 11, PongMessage > {· public: PongMessage() {} virtual void say() { printf("Pong\n"); } }; t_pfFactory MessageFactory::m_List[65536]; int main(int argc, char **argv) { Message *msg1; Message *msg2; msg1 = MessageFactory::Create(10); msg1->say(); msg2 = MessageFactory::Create(11); msg2->say(); delete msg1; delete msg2; return 0; } The template here does the magic by registering into the MessageFactory class, all new Message classes (e.g. PingMessage and PongMessage) that subclass from MessageTmpl. This works great and simplifies code maintenance but I still have some questions about this technique: Is this a known technique/pattern? what is the name? I want to search more info about it. I want to make the array for storing new constructors MessageFactory::m_List[65536] a std::map but doing so causes the program to segfault even before reaching main(). Creating an array of 65536 elements is overkill but I have not found a way to make this a dynamic container. For all message classes that are subclasses of MessageTmpl I have to implement the constructor. If not it won't register in the MessageFactory. For example commenting the constructor of the PongMessage: class PongMessage: public MessageTmpl < 11, PongMessage > { public: //PongMessage() {} /* HERE */ virtual void say() { printf("Pong\n"); } }; would result in the PongMessage class not being registered by the MessageFactory and the program would segfault in the MessageFactory::Create(11) line. The question is why the class won't register? Having to add the empty implementation of the 100+ messages I need feels inefficient and unnecessary.

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  • Parse lines of integers in C

    - by Jérôme
    This is a classical problem, but I can not find a simple solution. I have an input file like: 1 3 9 13 23 25 34 36 38 40 52 54 59 2 3 9 14 23 26 34 36 39 40 52 55 59 63 67 76 85 86 90 93 99 108 114 2 4 9 15 23 27 34 36 63 67 76 85 86 90 93 99 108 115 1 25 34 36 38 41 52 54 59 63 67 76 85 86 90 93 98 107 113 2 3 9 16 24 28 2 3 10 14 23 26 34 36 39 41 52 55 59 63 67 76 Lines of different number of integers separated by a space. I would like to parse them in an array, and separate each line with a marker, let say -1. The difficulty is that I must handle integers and line returns. Here my existing code, it loops upon the scanf loop (because scanf can not begin at a given position). #include <stdio.h> #include <stdlib.h> int main(int argc, char **argv) { if (argc != 4) { fprintf(stderr, "Usage: %s <data file> <nb transactions> <nb items>\n", argv[0]); return 1; } FILE * file; file = fopen (argv[1],"r"); if (file==NULL) { fprintf(stderr, "Error: can not open %s\n", argv[1]); fclose(file); return 1; } int nb_trans = atoi(argv[2]); int nb_items = atoi(argv[3]); int *bdd = malloc(sizeof(int) * (nb_trans + nb_items)); char line[1024]; int i = 0; while ( fgets(line, 1024, file) ) { int item; while ( sscanf (line, "%d ", &item )){ printf("%s %d %d\n", line, i, item); bdd[i++] = item; } bdd[i++] = -1; } for ( i = 0; i < nb_trans + nb_items; i++ ) { printf("%d ", bdd[i]); } printf("\n"); }

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  • dangling pointer, reason for value change after free()?

    - by Aman Jain
    In the following code segment, after free(x), why does y becomes 0? As per my understanding, the memory in the heap that was being pointed to by x, and is still being pointed by y, hasn't been allocated to someone else, so how can it change to 0? And moreover, I don't think it is free(x) that changed it to 0. Any comments? #include <stdio.h> int main ( int argc, char *argv[] ) { int *y = NULL; int *x = NULL; x = malloc(4); *x = 5; y = x; printf("[%d]\n", *y); //prints 5 free(x); printf("[%d]\n", *y); //why doesn't print 5?, prints 0 instead return 0; }

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  • How to efficently build an interpreter (lexer+parser) in C?

    - by Rizo
    I'm trying to make a meta-language for writing markup code (such as xml and html) wich can be directly embedded into C/C++ code. Here is a simple sample written in this language, I call it WDI (Web Development Interface): /* * Simple wdi/html sample source code */ #include <mySite> string name = "myName"; string toCapital(string str); html { head { title { mySiteTitle; } link(rel="stylesheet", href="style.css"); } body(id="default") { // Page content wrapper div(id="wrapper", class="some_class") { h1 { "Hello, " + toCapital(name) + "!"; } // Lists post ul(id="post_list") { for(post in posts) { li { a(href=post.getID()) { post.tilte; } } } } } } } Basically it is a C source with a user-friendly interface for html. As you can see the traditional tag-based style is substituted by C-like, with blocks delimited by curly braces. I need to build an interpreter to translate this code to html and posteriorly insert it into C, so that it can be compiled. The C part stays intact. Inside the wdi source it is not necessary to use prints, every return statement will be used for output (in printf function). The program's output will be clean html code. So, for example a heading 1 tag would be transformed like this: h1 { "Hello, " + toCapital(name) + "!"; } // would become: printf("<h1>Hello, %s!</h1>", toCapital(name)); My main goal is to create an interpreter to translate wdi source to html like this: tag(attributes) {content} = <tag attributes>content</tag> Secondly, html code returned by the interpreter has to be inserted into C code with printfs. Variables and functions that occur inside wdi should also be sorted in order to use them as printf parameters (the case of toCapital(name) in sample source). I am searching for efficient (I want to create a fast parser) way to create a lexer and parser for wdi. Already tried flex and bison, but as I am not sure if they are the best tools. Are there any good alternatives? What is the best way to create such an interpreter? Can you advise some brief literature on this issue?

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  • problem with NSInputStream on real iPhone

    - by ThamThang
    Hi guys, I have a problem with NSInputStream. Here is my code: case NSStreamEventHasBytesAvailable: printf("BYTE AVAILABLE\n"); int len = 0; NSMutableData *data = [[NSMutableData alloc] init]; uint8_t buffer[32768]; if(stream == iStream) { printf("Receiving...\n"); len = [iStream read:buffer maxLength:32768]; [data appendBytes:buffer length:len]; } [iStream close]; I try to read small data and it works perfectly on simulator and real iPhone. If I try to read large data (more than 4kB or maybe 5kB), the real iPhone just can read 2736 bytes and stop. Why is it? Help me plz! Merci d'avance!

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  • Autocorrelation method for pitch determination: what is the input data form?

    - by harsh
    I have read a code for pitch determination using autocorrelation method. Can anybody please tell what would be the input data (passed as argument to DetectPitch()) function here: double DetectPitch(short* data) { int sampleRate = 2048; //Create sine wave double *buffer = malloc(1024*sizeof(short)); double amplitude = 0.25 * 32768; //0.25 * max length of short double frequency = 726.0; for (int n = 0; n < 1024; n++) { buffer[n] = (short)(amplitude * sin((2 * 3.14159265 * n * frequency) / sampleRate)); } doHighPassFilter(data); printf("Pitch from sine wave: %f\n",detectPitchCalculation(buffer, 50.0, 1000.0, 1, 1)); printf("Pitch from mic: %f\n",detectPitchCalculation(data, 50.0, 1000.0, 1, 1)); return 0; }

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  • Why is javac 1.5 running so slowly compared with the Eclipse compiler?

    - by Simon Nickerson
    I have a Java Maven project with about 800 source files (some generated by javacc/JTB) which is taking a good 25 minutes to compile with javac. When I changed my pom.xml over to use the Eclipse compiler, it takes about 30 seconds to compile. Any suggestions as to why javac (1.5) is running so slowly? (I don't want to switch over to the Eclipse compiler permanently, as the plugin for Maven seems more than a little buggy.) I have a test case which easily reproduces the problem. The following code generates a number of source files in the default package. If you try to compile ImplementingClass.java with javac, it will seem to pause for an inordinately long time. import java.io.File; import java.io.FileNotFoundException; import java.io.PrintStream; public class CodeGenerator { private final static String PATH = System.getProperty("java.io.tmpdir"); private final static int NUM_TYPES = 1000; public static void main(String[] args) throws FileNotFoundException { PrintStream interfacePs = new PrintStream(PATH + File.separator + "Interface.java"); PrintStream abstractClassPs = new PrintStream(PATH + File.separator + "AbstractClass.java"); PrintStream implementingClassPs = new PrintStream(PATH + File.separator + "ImplementingClass.java"); interfacePs.println("public interface Interface<T> {"); abstractClassPs.println("public abstract class AbstractClass<T> implements Interface<T> {"); implementingClassPs.println("public class ImplementingClass extends AbstractClass<Object> {"); for (int i=0; i<NUM_TYPES; i++) { String nodeName = "Node" + i; PrintStream nodePs = new PrintStream(PATH + File.separator + nodeName + ".java"); nodePs.printf("public class %s { }\n", nodeName); nodePs.close(); interfacePs.printf("void visit(%s node, T obj);%n", nodeName); abstractClassPs.printf("public void visit(%s node, T obj) { System.out.println(obj.toString()); }%n", nodeName); } interfacePs.println("}"); abstractClassPs.println("}"); implementingClassPs.println("}"); interfacePs.close(); abstractClassPs.close(); implementingClassPs.close(); } }

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  • c windows connect() fails. error 10049

    - by Joshua Moore
    The following two pieces of code compile, but I get a connect() failed error on the client side. (compiled with MinGW). Client Code: // thanks to cs.baylor.edu/~donahoo/practical/CSockets/code/TCPEchoClientWS.c #include <stdio.h> #include <winsock.h> #include <stdlib.h> #define RCVBUFSIZE 32 // size of receive buffer void DieWithError(char *errorMessage); int main(int argc, char* argv[]) { int sock; struct sockaddr_in echoServAddr; unsigned short echoServPort; char *servIP; char *echoString; char echoBuffer[RCVBUFSIZE]; int echoStringLen; int bytesRcvd, totalBytesRcvd; WSAData wsaData; if((argc < 3) || (argc > 4)){ fprintf(stderr, "Usage: %s <Sever IP> <Echo Word> [<Echo Port>]\n", argv[0]); exit(1); } if (argc==4) echoServPort = atoi(argv[3]); // use given port if any else echoServPort = 7; // echo is well-known port for echo service if(WSAStartup(MAKEWORD(2, 0), &wsaData) != 0){ // load winsock 2.0 dll fprintf(stderr, "WSAStartup() failed"); exit(1); } // create reliable, stream socket using tcp if((sock=socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) DieWithError("socket() failed"); // construct the server address structure memset(&echoServAddr, 0, sizeof(echoServAddr)); echoServAddr.sin_family = AF_INET; echoServAddr.sin_addr.s_addr = inet_addr(servIP); // server IP address echoServAddr.sin_port = htons(echoServPort); // establish connection to the echo server if(connect(sock, (struct sockaddr*)&echoServAddr, sizeof(echoServAddr)) < 0) DieWithError("connect() failed"); echoStringLen = strlen(echoString); // determine input length // send the string, includeing the null terminator to the server if(send(sock, echoString, echoStringLen, 0)!= echoStringLen) DieWithError("send() sent a different number of bytes than expected"); totalBytesRcvd = 0; printf("Received: "); // setup to print the echoed string while(totalBytesRcvd < echoStringLen){ // receive up to the buffer size (minus 1 to leave space for a null terminator) bytes from the sender if(bytesRcvd = recv(sock, echoBuffer, RCVBUFSIZE-1, 0) <= 0) DieWithError("recv() failed or connection closed prematurely"); totalBytesRcvd += bytesRcvd; // keep tally of total bytes echoBuffer[bytesRcvd] = '\0'; printf("%s", echoBuffer); // print the echo buffer } printf("\n"); closesocket(sock); WSACleanup(); exit(0); } void DieWithError(char *errorMessage) { fprintf(stderr, "%s: %d\n", errorMessage, WSAGetLastError()); exit(1); } Server Code: // thanks cs.baylor.edu/~donahoo/practical/CSockets/code/TCPEchoServerWS.c #include <stdio.h> #include <winsock.h> #include <stdlib.h> #define MAXPENDING 5 // maximum outstanding connection requests #define RCVBUFSIZE 1000 void DieWithError(char *errorMessage); void HandleTCPClient(int clntSocket); // tcp client handling function int main(int argc, char **argv) { int serverSock; int clientSock; struct sockaddr_in echoServerAddr; struct sockaddr_in echoClientAddr; unsigned short echoServerPort; int clientLen; // length of client address data structure WSAData wsaData; if (argc!=2){ fprintf(stderr, "Usage: %s <Server Port>\n", argv[0]); exit(1); } echoServerPort = atoi(argv[1]); if(WSAStartup(MAKEWORD(2, 0), &wsaData)!=0){ fprintf(stderr, "WSAStartup() failed"); exit(1); } // create socket for incoming connections if((serverSock=socket(PF_INET, SOCK_STREAM, IPPROTO_TCP))<0) DieWithError("socket() failed"); // construct local address structure memset(&echoServerAddr, 0, sizeof(echoServerAddr)); echoServerAddr.sin_family = AF_INET; echoServerAddr.sin_addr.s_addr = htonl(INADDR_ANY); // any incoming interface echoServerAddr.sin_port = htons(echoServerPort); // local port // bind to the local address if(bind(serverSock, (struct sockaddr*)&echoServerAddr, sizeof(echoServerAddr) )<0) DieWithError("bind() failed"); // mark the socket so it will listen for incoming connections if(listen(serverSock, MAXPENDING)<0) DieWithError("listen() failed"); for (;;){ // run forever // set the size of the in-out parameter clientLen = sizeof(echoClientAddr); // wait for a client to connect if((clientSock = accept(serverSock, (struct sockaddr*)&echoClientAddr, &clientLen)) < 0) DieWithError("accept() failed"); // clientSock is connected to a client printf("Handling client %s\n", inet_ntoa(echoClientAddr.sin_addr)); HandleTCPClient(clientSock); } // NOT REACHED } void DieWithError(char *errorMessage) { fprintf(stderr, "%s: %d\n", errorMessage, WSAGetLastError()); exit(1); } void HandleTCPClient(int clientSocket) { char echoBuffer[RCVBUFSIZE]; // buffer for echostring int recvMsgSize; // size of received message // receive message from client if((recvMsgSize = recv(clientSocket, echoBuffer, RCVBUFSIZE, 0) <0)) DieWithError("recv() failed"); // send received string and receive again until end of transmission while(recvMsgSize > 0){ // echo message back to client if(send(clientSocket, echoBuffer, recvMsgSize, 0)!=recvMsgSize) DieWithError("send() failed"); // see if there's more data to receive if((recvMsgSize = recv(clientSocket, echoBuffer, RCVBUFSIZE, 0)) <0) DieWithError("recv() failed"); } closesocket(clientSocket); // close client socket } How can I fix this?

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  • Which header files are necessary to run this code snippet?

    - by httpinterpret
    It's from here,but fails when compiling: int main(int argc, char **argv) { struct hostent { char *h_name; // main name char **h_aliases; // alternative names (aliases) int h_addrtype; // address type (usually AF_INET) int h_length; // length of address (in octets) char **h_addr_list; // alternate addresses (in Network Byte Order) }; #define h_addr h_addr_list[0] // First address of h_addr_list. struct hostent *info_stackoverflow; int i = 0; info_stackoverflow = gethostbyname( "www.stackoverflow.com" ); printf("The IP address of %s is %s", info_stackoverflow->h_name, inet_ntoa( * ((struct in_addr *)info_stackoverflow->h_addr ))); /* aliases */ while( *(pc_ip->h_aliases + i) != NULL ) { printf("\n\tAlias: %s", *(pc_ip->h_aliases + i) ); i++; } }

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  • How to take input for a character pointer without using fget?

    - by ashish yadav
    consider the code #include<stdio.h> int main() { char* a; scanf("%s",a);//&a and &a[0] give same results-crashes printf("%s",); return 0; } why does this code results in crashing?whereas this code using character array works fine? #include<stdio.h> int main() { char a[100]; scanf("%s",&a[0]);//works fine printf("%s",a); return 0; } the difference being character array and pointer?but i knew that pointer just points to the first element that is &a[0] should work fine but upper code crashes for all three that is a,&a and &a[0]? the main thing i would to gather is how can i take input of a character pointer if i insist on using scanf only? i apologize if i am not clear. thanks in advance:)

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  • How do I define an implicit typecast from my class to a scalar?

    - by Delan Azabani
    I have the following code, which uses a Unicode string class from a library that I'm writing: #include <cstdio> #include "ucpp" main() { ustring a = "test"; ustring b = "ing"; ustring c = "- -"; ustring d; d = "cafe\xcc\x81"; printf("%s\n", (a + b + c[1] + d).encode()); } The encode method of the ustring class instances converts the internal Unicode into a UTF-8 char *. However, because I don't have access to the char class definition, I am unsure on how I can define an implicit typecast (so that I don't have to manually call encode when using with printf, etc).

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  • Argc/Argv C Problems

    - by Salman
    Hey all, If I have the following code: main(int argc, char *argv[]){ char serveradd[20]; strcpy(serveradd, argv[1]); int port = atoi(argv[2]); printf("%s %d \n", serveradd, port); The first two arguments to the command line are printed. However, if I do this: char serveradd[20]; strcpy(serveradd, argv[1]); int port = atoi(argv[2]); char versionnum[1]; strcpy(versionnum, argv[3]); printf("%s %d %s \n", serveradd, port, versionnum);` The first argument (serveradd) does not print out to the screen and is not being stored... Why is this happening and how can I fix it? Thanks!

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  • Problem passing a reference as a named parameter to a variadic function

    - by Michael Mrozek
    I'm having problems in Visual Studio 2003 with the following: void foo(const char*& str, ...) { va_list args; va_start(args, str); const char* foo; while((foo = va_arg(args, const char*)) != NULL) { printf("%s\n", foo); } } When I call it: const char* one = "one"; foo(one, "two", "three", NULL); I get: Access violation reading location 0xcccccccc on the printf() line -- va_arg() returned 0xcccccccc. I finally discovered it's the first parameter being a reference that breaks it -- if I make it a normal char* everything is fine. It doesn't seem to matter what the type is; being a reference causes it to fail at runtime. Is this a known problem with VS2003, or is there some way in which that's legal behavior? It doesn't happen in GCC; I haven't tested with newer Visual Studios to see if the behavior goes away

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  • Data loss between conversion

    - by Alex Brooks
    Why is it that I loose data between the conversions below even though both types take up the same amount of space? If the conversion was done bitwise, it should be true that x = z unless data is being stripped during the conversion, right? Is there a way to do the two conversions without losing data (i.e. so that x = z)? main.cpp: #include <stdio.h> #include <stdint.h> int main() { double x = 5.5; uint64_t y = static_cast<uint64_t>(x); double z = static_cast<double>(y) // Desire : z = 5.5; printf("Size of double: %lu\nSize of uint64_t: %lu\n", sizeof(double), sizeof(uint64_t)); printf("%f\n%lu\n%f\n", x, y, z); } Results: Size of double: 8 Size of uint64_t: 8 5.500000 5 5.000000

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  • print address of virtual member function

    - by hidayat
    I am trying to print the address of a virtual member function. If I only wants to print the address of the function I can write: print("address: %p", &A::func); But I want to do something like this: A *b = new B(); printf("address: %p", &b->func); printf("address: %p", &b->A::func); however this does not compile, is it possible to do something like this even do looking up the address in the vtable is done in runtime?

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  • use callback function to report stack backtrace

    - by user353394
    Assume I have the following: typedef struct { char *name; char binding; int address; } Fn_Symbol //definition of function symbol static Fn_Symbol *fnSymbols; //array of function symbols in a file statc int total; //number of symbol functions in the array and file static void PrintBacktrace(int sigum, siginfo_t * siginfo, void *context) { printf("\nSignal received %d (%s)\n", signum, strsignal(signum)); const int eip_index = 14; void *eip = (void *)((struct ucontext *)context)->uc_mcontext.gregs[eip_index]; printf("Error at [%p] %s (+0x%x), eip, fnName, offset from start); //????? exit(0); } I have this so far, but what is the best way using the fnSymbols static global pointer to identify the function where the error occured and then back trace through the stack to identify each calling function by address, name, and offset?

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  • Pointer to local variable

    - by Radek Šimko
    May I have any acces to local variable in different function? If may, how? void replaceNumberAndPrint(int array[3]) { printf("%i\n", array[1]); printf("%i\n", array[1]); } int * getArray() { int myArray[3] = {4, 65, 23}; return myArray; } int main() { replaceNumberAndPrint(getArray()); } The output of the piece of code above: 65 4202656 What am i doing wrong? What the "4202656" means?? Do I have to copy the whole array in the replaceNumberAndPrint() function to be able to access to it more than first times?

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