[Bug c/21749] New: gcc generates wrong code

[Bug c/21749] New: gcc generates wrong code

[sunmoon1997 at gmail dot com]

the source code:
#include <stdio.h>
#include <stdlib.h>

typedef struct test_st {
        char *name;
        int  num;
} test_t;

static char * str[] = {
        "one",
        "two",
        "three",
        "four",
        "five",
        "six",
        "seven"
};

char * get_rand_str () {
        char *s = str[rand () % (sizeof(str) / sizeof(str[0]))];
        return s;
}

int main () {
        char * s [10] = {NULL};
        int  i = 0;
        test_t test_struct[]= {
                {
                        .name = s[i] = get_rand_str(),
                        .num = i++,
                },
                {
                        .name = s[i] = get_rand_str(),
                        .num = i++,
                },
                {
                        .name = s[i] = get_rand_str(),
                        .num = i++,
                },
                {
                        .name = s[i] = get_rand_str(),
                        .num = i++,
                },
                {
                        .name = s[i] = get_rand_str(),
                        .num = i++,
                },
        };

        printf ("i = %d\n", i);
        for (i = 0; i < sizeof (test_struct) / sizeof(test_struct[0]); i ++) {
                printf ("name `%s\' num \'%d\' s[%d] = `%s\'\n",
test_struct[i].name, test_struct[i].num, i, s[i]);
        }

        return 0;
}
compiling with gcc4
smspc tmp # LANG=C LC_ALL=C gcc -Wall  test_struct_array.c  -g
then run it i got unexpected result:
smspc tmp # ./a.out
i = 5
name `two' num '0' s[0] = `two'
name `five' num '0' s[1] = `(null)'
name `three' num '0' s[2] = `(null)'
name `six' num '0' s[3] = `(null)'
name `two' num '0' s[4] = `(null)'
gcc -v
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: /usr/tmpdir/portage/gcc-4.0.0.20050522/work/gcc-4.0.0/configure
--enable-version-specific-runtime-libs --prefix=/usr
--bindir=/usr/i686-pc-linux-gnu/gcc-bin/4.0.0-20050522
--includedir=/usr/lib/gcc/i686-pc-linux-gnu/4.0.0-20050522/include
--datadir=/usr/share/gcc-data/i686-pc-linux-gnu/4.0.0-20050522
--mandir=/usr/share/gcc-data/i686-pc-linux-gnu/4.0.0-20050522/man
--infodir=/usr/share/gcc-data/i686-pc-linux-gnu/4.0.0-20050522/info
--with-gxx-include-dir=/usr/lib/gcc/i686-pc-linux-gnu/4.0.0-20050522/include/g++-v4
--host=i686-pc-linux-gnu --build=i686-pc-linux-gnu --disable-altivec
--enable-nls --without-included-gettext --with-system-zlib --disable-checking
--disable-werror --disable-libunwind-exceptions --disable-multilib
--enable-java-awt=gtk --enable-languages=c,c++,objc,java,f95 --enable-shared
--enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
Thread model: posix
gcc version 4.0.0-20050522 (Gentoo 4.0.0.20050522)
compiling with gcc34 got following result as expect:
smspc tmp # LANG=C LC_ALL=C gcc -Wall  test_struct_array.c  -g
smspc tmp # ./a.out
i = 5
name `two' num '0' s[0] = `two'
name `five' num '1' s[1] = `five'
name `three' num '2' s[2] = `three'
name `six' num '3' s[3] = `six'
name `two' num '4' s[4] = `two'

-- 
           Summary: gcc generates wrong code
           Product: gcc
           Version: 4.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sunmoon1997 at gmail dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21749

[Bug c/21749] gcc generates wrong code

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-05-25 12:05 -------
This is undefined code:
        test_t test_struct[]= {
                {
                        .name = s[i] = get_rand_str(),
                        .num = i++,
                },
                {
                        .name = s[i] = get_rand_str(),
                        .num = i++,
                },
                {
                        .name = s[i] = get_rand_str(),
                        .num = i++,
                },
                {
                        .name = s[i] = get_rand_str(),
                        .num = i++,
                },
                {
                        .name = s[i] = get_rand_str(),
                        .num = i++,
                },
        };

the order which i++ and get_rand_str() is called is undefined.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21749

[Bug c/21749] gcc generates wrong code

[sunmoon1997 at gmail dot com]

------- Additional Comments From sunmoon1997 at gmail dot com  2005-05-25 12:51 -------
thanks for replay

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21749