Error compilation

[Golum]

Hello guys!
Well.... it`s my code (c++/linux)

#include <arpa/inet.h>  
#include <string.h>             
#include <stdio.h>              
#include <errno.h>              
#include <unistd.h>             
#include <stdlib.h>    
#include <pthread.h>
#include <ncurses.h>
 
     void *ReadMsg(int fd);
     void *WriteMsg(int fd);    
 
int main(int argc, char* argv[])
{     
    pthread_t thread;
    int sockfd;
    char sendline[1000],recvline[1000]; 
    struct sockaddr_in addr;    
    bzero(sendline,1000);
    bzero(recvline,1000);    
    if((sockfd = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
        perror("socket"); 
        exit( -1);
    }   
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(51000);   
    if(connect(sockfd, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
        perror("connect");
        close(sockfd);
        exit( -1);
    }    
     printf("Connect is done!\n");
    //Создание потоков    
    if (pthread_create(&thread, NULL, ReadMsg, (void*) sockfd) != 0) return EXIT_FAILURE;
    if (pthread_create(&thread, NULL, WriteMsg, (void*) sockfd) != 0) return EXIT_FAILURE;   
    while (1);
    close(sockfd);
}
 void *ReadMsg(int fd) {
    int n;
    char recvline[1000];
    while (1) {
        n = read(fd,recvline, 999);
        printf("<< %s", recvline);
    }
} /* ReadMsg */
 void *WriteMsg(int fd)
{
    char sendline[1000];
    int n;
    while ( 1 ) {
        fgets(sendline, 1000, stdin);
        if( (n = write(fd, sendline, strlen(sendline)+1)) < 0) {
            perror("Can\'t write\n");
            close(fd);
            exit(1);
        }
    }
} /* WriteMsg */
 

my problems:
client1.cpp: In function ‘int main(int, char**)’:
client1.cpp:35: error: invalid conversion from ‘void* (*)(int)’ to ‘void* (*)(void*)’
client1.cpp:35: error: initializing argument 3 of ‘int pthread_create(pthread_t*, const pthread_attr_t*, void* (*)(void*), void*)’
client1.cpp:36: error: invalid conversion from ‘void* (*)(int)’ to ‘void* (*)(void*)’
client1.cpp:36: error: initializing argument 3 of ‘int pthread_create(pthread_t*, const pthread_attr_t*, void* (*)(void*), void*)’


Please help me!

[Golum]

Anybody will answer? It is very necessary!

[Banfa]

Try "man pthread_create" at you command line and you will find that the third parameter should be a pointer to a function with the prototype

void* threadFunction(void* parameter);

not a pointer to a function with the prototype

void* threadFunction(int parameter);

as you have defined them. The 2 different function pointers are incompatible.

You need to change ReadMsg and WriteMsg.

[Banfa]

Anybody will answer? It is very necessary!

Please note that this is an international forum and there is no guarantee that the person that knows the answre to your question is awake at the time you post it. This forums ettiquette didtates that you should wait at least 24 hours before badgering us with extra posts demanding an answer.

[Golum]

I`m so sorry...

#include <arpa/inet.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <pthread.h>
#include <ncurses.h>
 
#include <string>
#include <iostream>
 
void *ReadMsg(void* pfd);
void *WriteMsg(void* pfd);
volatile bool quit = false;
 
int main(int argc, char* argv[])
{
    pthread_t rthread;
    pthread_t wthread;
    int sockfd;
    char sendline[1000],recvline[1000];
    struct sockaddr_in addr;
    bzero(sendline,1000);
    bzero(recvline,1000);
    if((sockfd = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
        perror("socket");
        exit( -1);
    }
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(51000);
    if(connect(sockfd, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
        perror("connect");
        close(sockfd);
        exit( -1);
    }
    printf("Connect is done!\n");
    //Создание потоков
    if (pthread_create(&rthread, NULL, ReadMsg, (void*) sockfd) != 0) return EXIT_FAILURE;
    if (pthread_create(&wthread, NULL, WriteMsg, (void*) sockfd) != 0) return EXIT_FAILURE;
 
    std::string str;
    while ( std::cin >> str ) {
        if ( str == "quit" ) {
            quit = true;
            break;
        }
    }
 
    pthread_join(rthread, NULL);
    pthread_join(wthread, NULL);
 
    close(sockfd);
    return 0;
}
void *ReadMsg(void* pfd) {
    int n;
    int fd = * ((int* ) pfd);
    char recvline[1000];
    while (1) {
        if ( quit ) return NULL;
        n = read(fd,recvline, 999);
        printf("<< %s", recvline);
    }
} /* ReadMsg */
void *WriteMsg(void* pfd)
{
    char sendline[1000];
    int n;
    int fd = * ((int* ) pfd);
    while ( 1 ) {
        if ( quit ) return NULL;
        fgets(sendline, 1000, stdin);
        if( (n = write(fd, sendline, strlen(sendline)+1)) < 0) {
            perror("Can\'t write\n");
            close(fd);
            exit(1);
        }
    }
} /* WriteMsg */
 

It is compiled well, but at start there is a segmentation error! What not so?

[newb16]

It's hard to say what (is) "not so" here - it exits after perror("connect"); Maybe it's just cygwin to blame, I don't know.

[Banfa]

In lines 40 and 41 you pass (void*) sockfd, that is a socket file descriptor (int) cast to a void*.

At lines 59 and 71 you access the parameter as * ((int* ) pfd), that is you treat it as a pointer to an int. But it was never a pointer to an int it was an int so you dereference some low invalid address in memory. That I imagine is causing the segmentation error.

If you are going to cast an int to a void*, which is what I would do, then on the other side you need to do the reverse, cast a void* to an int. Not treat it as if its a valid pointer.