a strange segment fault about ltp-posix test

yanglei_fage · #1 (**permalink**) 06-24-2009

Hi all

In the ltp-posix test,there is a case in open_posix_testsuite\conformance\interfaces\timer_gettime\speculative/6-1.c

Quote:

#include <time.h>
#include <stdio.h>
#include <errno.h>
//#include "posixtest.h"
#define BOGUSTID 9999
int main(int argc, char *argv[])
{
timer_t tid;
struct itimerspec its;
tid = (timer_t) BOGUSTID;

if (timer_gettime(tid, &its) == -1) {
if (EINVAL == errno) {
printf("fcn returned -1 and errno==EINVAL\n");
//return PTS_PASS;
} else {
printf("fcn returned -1 but errno!=EINVAL\n");
printf("Test FAILED\n");
//return PTS_FAIL;
}
}
printf("fcn did not return -1\n");
//return PTS_PASS;
}

I run the above code,it will has a segment fault, if I modify it to below,it works well

Quote:

#include <time.h>
#include <stdio.h>
#include <errno.h>
//#include "posixtest.h"
#define BOGUSTID 9999
int main(int argc, char *argv[])
{
timer_t tid;
struct itimerspec its;
int tval=BOGUSTID;
printf("%d\n",tval);
tid = (timer_t) &tval;
printf("%d\n",tid);
if (timer_gettime(tid, &its) == -1) {
if (EINVAL == errno) {
printf("fcn returned -1 and errno==EINVAL\n");
//return PTS_PASS;
} else {
printf("fcn returned -1 but errno!=EINVAL\n");
printf("Test FAILED\n");
//return PTS_FAIL;
}
}
printf("fcn did not return -1\n");
// return PTS_PASS;
}

Anybody can tell me why?

fpmurphy · #2 (**permalink**) 06-24-2009

Reducing the problem to its essence makes it easier to understand

Code:

#include <time.h>
#define BOGUSTID 9999

timer_t tid;
  
#if WANT_SEG_FAULT
   tid = (timer_t) BOGUSTID
#else
   int tval=BOGUSTID;
   tid = (timer_t) &tval;
#endif

The correct header is being included but an assumption is being made that tid is capable of storing a value as shown above. Generally this assumption is wrong as timer_t is specified to be an opaque type in POSIX.1. On most versions of GNU/Linux, timer_t is actually defined by

Code:

#define timer_t   void *

In your example you are trying to stuff 9999 into a void * - which is not on.

BTW, your workaround is defective also. tid is not being set to 9999 but to the address of tval.

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