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[vox-tech] another glibc bug?
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[vox-tech] another glibc bug?

before i post this to glibc-bug, i'd like to post this just in case
somebody has more information about this:

#include <malloc.h>
#include <stdio.h>
#include <stdlib.h>
#include <mcheck.h>
// On my system, size_t is an unsigned int.

int main(void)
   char *p = (char *) malloc(sizeof(char));

   if (p == NULL)

   printf("I requested %u bytes.\n", sizeof(char));
   printf("p was allocated %u bytes.\n", malloc_usable_size(p));

   return 0;

the problem is that linking with libmcheck.a seems to completely confuse
calls to malloc_usable_size():

   $ gcc -W -Wall try.c 
   $ ./a.out 
   I requested 1 bytes.
   p was allocated 12 bytes.

   $ gcc -W -Wall try.c -lmcheck
   $ ./a.out 
   I requested 1 bytes.
   p was allocated 4141754496 bytes.

of course, i don't have this amount of memory on my system.


ps- the patch for the last bug in glibc that i found, malloc_stats()
segfaulting before memory was allocated, was just accepted and will be
in the next release.

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