Segmentation fault generated by mkfifo() in C

Question

I've been trying to debug this for a few hours now and I'm still stuck...

I get a segmentation fault with a "mkfifo" call in this code (it is only a part of my entire code, since I figured the rest was not relevant here) :

#include "marketfunc.h"
#include "error.h"
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>

#define PIPE_PATH "./pipe.fifo"

struct myStruct
{
    int x;      
    int y;
    int z;  
};


struct myStruct *s;

int main(int argc, char **argv)
{

    s = malloc(sizeof(struct myStruct));

    // 'int marketfunc_init(int x)' is defined in a perfectly working extern library
    if(marketfunc_init(1) == -1) error("failed to initialize marketfunc library", 5);

    printf("test1\n");

    // Segmentation fault
    if(mkfifo(PIPE_PATH, 0666) == -1) error("failed to create pipe", 1);

    printf("test2\n");

    //...

}

Which produces this output (executableFile beeing the name of my file):

test1
bin/executableFile: Segmentation fault (core dumped)

The gdb backtrace produces this:

#0  strchrnul () at ../sysdeps/x86_64/strchr.S:32
#1  0x00007ffff7a5ed82 in __find_specmb (format=0xffffffffffffff60 <error: Cannot access memory at address 0xffffffffffffff60>)
    at printf-parse.h:108
#2  _IO_vfprintf_internal (s=0x7fffffffb5a0, format=0xffffffffffffff60 <error: Cannot access memory at address 0xffffffffffffff60>, 
    ap=0x7fffffffdd58) at vfprintf.c:1332
#3  0x00007ffff7a63f31 in buffered_vfprintf (s=s@entry=0x7ffff7dd41c0 <_IO_2_1_stderr_>, 
    format=format@entry=0xffffffffffffff60 <error: Cannot access memory at address 0xffffffffffffff60>, args=args@entry=0x7fffffffdd58)
    at vfprintf.c:2356
#4  0x00007ffff7a5eeae in _IO_vfprintf_internal (s=0x7ffff7dd41c0 <_IO_2_1_stderr_>, 
    format=format@entry=0xffffffffffffff60 <error: Cannot access memory at address 0xffffffffffffff60>, ap=ap@entry=0x7fffffffdd58)
    at vfprintf.c:1313
#5  0x00007ffff7b0c595 in error_tail (status=status@entry=4199947, errnum=errnum@entry=1, 
    message=message@entry=0xffffffffffffff60 <error: Cannot access memory at address 0xffffffffffffff60>, args=args@entry=0x7fffffffdd58)
    at error.c:201
#6  0x00007ffff7b0c6ed in __error (status=4199947, errnum=1, 
    message=0xffffffffffffff60 <error: Cannot access memory at address 0xffffffffffffff60>) at error.c:251
#7  0x0000000000400b78 in main (argc=1, argv=0x7fffffffdf38) at src/executableFile.c:75

Though the "pipe.fifo" file is created... Thanks in advance for your help !

EDIT:

error is simply defined as such in error.c and it's signature in error.h:

#include "error.h"
#include <stdlib.h>
#include <stdio.h>

void error(char *msg, int ret)
{
    perror(msg);
    exit(ret);
}

It looks like `error` is the culprit, but we don't know how it is defined — Basile Starynkevitch, Dec 26 '15 at 17:47
`REQUESTS_PIPE_PATH` or `PIPE_PATH`? Is `s` a pointer to a structure, or an actual structure instance? Things like these will distract from the actual problem you have, please learn how to create a [Minimal, Complete, and Verifiable Example](http://stackoverflow.com/help/mcve). — Some programmer dude, Dec 26 '15 at 17:48
The purposes of MCVE are several: the problem can be easily replicated by commenters (or not); you don't assume "the rest of the code does not cause the bug" (since you don't *know* where the bug is); and quite often, preparing the MCVE will reveal to you what the problem is, as you do it. — Weather Vane, Dec 26 '15 at 17:51
I've edited the post to clarify a bit. Thanks for your quick answers. — Guillaume Hartenstein, Dec 26 '15 at 17:54
In `s = malloc(sizeof(struct myStruct));`the struct variable `s` is not a pointer. Do you have warnings enabled? — Weather Vane, Dec 26 '15 at 17:56
And in any case you have at least one typo `struct myStruc s;`. Please don't tinker with this on-the-fly: post the MCVE requested. — Weather Vane, Dec 26 '15 at 18:00
It is a good idea to always include your own include files **after** the system include files. `error` might be defined in one of the system include files. — chqrlie, Dec 26 '15 at 18:14
Oh yes, my bad thanks for the reminder :) I just modified this in my code, but it didn't solve the problem :/ — Guillaume Hartenstein, Dec 26 '15 at 18:28

score 0 · Accepted Answer · answered Dec 26 '15 at 19:01

If you look at the stack trace, you will see that the call to error() shows up as:

0x00007ffff7b0c6ed in __error (status=4199947, errnum=1, message=0xffffffffffffff60 <error: Cannot access memory at address 0xffffffffffffff60>) at error.c:251

This is NOT the error() function that you defined. But rather, it is the error() function defined in error.h with the following signature:

void error(int status, int errnum, const char *format, ...);

See error.h.

As you can see, this function expects a char* format as the last argument, which is getting some junk off the stack 0xffffffffffffff60, because you don't pass in the third argument at all. It would seem that the linker is resolving the call to error() to the wrong function.

As a quick fix, I would rename things as follows:

rename your file `error.h` to `error_my.h`

your definition of `error()` to, say, `error_my()`

replace the calls to `error()` with `error_my()`.

Your code would look like:

#include "marketfunc.h"
#include "error_my.h" // <=======================
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>

#define PIPE_PATH "./pipe.fifo"

struct myStruct
{
    int x;      
    int y;
    int z;  
};


struct myStruct *s;

int main(int argc, char **argv)
{

    s = malloc(sizeof(struct myStruct));

    // 'int marketfunc_init(int x)' is defined in a perfectly working extern library
    if(marketfunc_init(1) == -1) error_my("failed to initialize marketfunc library", 5); // <=======================

    printf("test1\n");

    // Segmentation fault
    if(mkfifo(PIPE_PATH, 0666) == -1) error_my("failed to create pipe", 1); // <=======================

    printf("test2\n");

    //...

}

Print out errno when mkfifo() fails to figure out why it is failing in the first place.

Thanks very much, that fixed the issue ! I was so focused on the mkfifo call that I didn't even think about checking this... — Guillaume Hartenstein, Dec 26 '15 at 20:36

Segmentation fault generated by mkfifo() in C

1 Answers1