[Bug c/43219] New: O2, O3 and Os produce wrong code

[vierhaus at physik dot hu-berlin dot de]

LC_ALL=C gcc -v
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.3.2-1.1'
--with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.3
--program-suffix=-4.3 --enable-clocale=gnu --enable-libstdcxx-debug
--enable-objc-gc --enable-mpfr --enable-cld --enable-checking=release
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.3.2 (Debian 4.3.2-1.1)


The following code
#include <stdlib.h>
#include <stdio.h>

int main() {

  int i;
  double R4 = 0;
  int *activedirections;
  int nactive=0;
  int holder;
  activedirections = malloc(sizeof(int));
  activedirections[0] = 0;
  nactive = 0;

  for (i=1; i<=1; i=i+1) {
      activedirections[nactive] = i;
      nactive = nactive + 1;
  }

  holder = activedirections[0];
  printf("activedirections[0] = %i\n",activedirections[0]);
  printf("activedirections[0] = %i\n",activedirections[0]);
  printf("holder              = %i\n",holder);
  free(activedirections);
}

produces the output:

activedirections[0] = 0
activedirections[0] = 1
holder              = 0

when compiling with (gcc version 4.3.2)
gcc -O3 prog.c
gcc -O2 prog.c
gcc -Os prog.c

and the output

activedirections[0] = 1
activedirections[0] = 1
holder              = 1

when compiled with -O1 or -O0 or when compiled with gcc-4.2.4 or gcc-4.1.3 on
any optimization level. The latter is latter case is what I would expect.
There is no compiler output in all cases.

I will not paste the 1600 lines of prog.i in here and can not see how to attach
the file to the report... ?


-- 
           Summary: O2, O3 and Os produce wrong code
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: vierhaus at physik dot hu-berlin dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43219