[Bug c/19354] New: -O3 -Wunreachable-code failing

[alex at ergens dot op dot het dot net]

When combining "-Wunreachable-code" with any optimizing above zero, "warning:
will never be executed" under certain circumstances.

I've managed to create a small program that does show this bug, unless "nobug"
is defined when compiling.

$ gcc -v
Reading specs from /usr/lib/gcc/i386-redhat-linux/3.4.2/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--disable-checking --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-java-awt=gtk --host=i386-redhat-linux
Thread model: posix
gcc version 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)

$ make
cc -O3 -Wunreachable-code -save-temps    test.c   -o test
test.c: In function `x':
test.c:5: warning: will never be executed

$ cat test.i
# 1 "test.c"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "test.c"
int x(int i,int *j) {
 *j = i;

 if (*j > 31) {
  printf("statement is executed\n");
 } else {



  return 1;
 }
 return 0;
}

int main(int argc,char *argv[]) {
 int i,j,k;

 if (argc != 2) {
  printf("Usage: test <integer>\n");
  return 1;
 } else {
  i=atoi(argv[1]);
 }

 k=x(i,&j);
 printf("j is now:  %i\n",j);
}




$ ./test 123
statement is executed
j is now:  123
$ ./test 1
j is now:  1


rm test
mv test.i test.i.old


$ cc -O3 -Wunreachable-code -save-temps    test.c   -o test -Dnobug
$ diff test.i test.i.old
12c12
<   printf("statement is not executed\n");
---
>



In case it isn't clear:  my test.c program contains:

        } else {
#ifdef nobug
                printf("statement is not executed\n");
#endif
                return 1;
        }

-- 
           Summary: -O3 -Wunreachable-code failing
           Product: gcc
           Version: 3.4.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: alex at ergens dot op dot het dot net
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19354