[Bug 993193] Re: Error with Valgrind on variadic functions

[bnuytten]

va_list list = {{0}}; /*
	quick&dirty, avoids valgrind messages:
	- Conditional jump or move depends on uninitialised value(s)
	- Use of uninitialised value of size 8
	compiler warning: extended initializer lists only available with -std=c++0x or -std=gnu++0x
	*/

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https://bugs.launchpad.net/bugs/993193

Title:
  Error with Valgrind on variadic functions

Status in “gcc-defaults” package in Ubuntu:
  Confirmed

Bug description:
  I'm using Ubuntu 12.10 dev with gcc 4:4.7.0-5ubuntu1 and valgrind
  1:3.7.0-0ubuntu3. Here is the code example:

  #include <stdarg.h>
  #include <stdio.h>

  void test(char *var1, char *var2, char *var3, char *var4, char *var5, char *var6, int argc, ...)
  {
   va_list list;

   va_start(list, argc);
   if(va_arg(list, long int) == 1)
    printf("Test\n");
   va_end(list);
  }

  int main()
  {
   test(NULL, NULL, NULL, NULL, NULL, NULL, 1, 1);
   return 0;
  }

  
  I have compiled it with "gcc -O3 -Wall -Wextra -o test -pedantic test.c" and tested with "valgrind ./test". The output is:

  ==11060== Memcheck, a memory error detector
  ==11060== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
  ==11060== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
  ==11060== Command: ./test
  ==11060==
  ==11060== Conditional jump or move depends on uninitialised value(s)
  ==11060==    at 0x400575: test (in /home/sworddragon/data/test)
  ==11060==    by 0x400437: main (in /home/sworddragon/data/test)
  ==11060==
  Test
  ==11060==
  ==11060== HEAP SUMMARY:
  ==11060==     in use at exit: 0 bytes in 0 blocks
  ==11060==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
  ==11060==
  ==11060== All heap blocks were freed -- no leaks are possible
  ==11060==
  ==11060== For counts of detected and suppressed errors, rerun with: -v
  ==11060== Use --track-origins=yes to see where uninitialised values come from
  ==11060== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 2 from 2)

  
  Interestingly with 5 instead of 6 char * arguments before I'm getting the same error but without the output "Test". WIth less than 5 char * arguments before all is working fine.

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