[Bug middle-end/35188] Missing a warning: inherently false expressions

[tuttle at sandbox dot cz]

------- Comment #5 from tuttle at sandbox dot cz  2008-02-16 14:12 -------
I think we could generalize a bit: This in fact is not bound to if-statement or
code reachability.

Tried the following with snapshot gcc-4.3-20080215 -Wextra -Wall
-Wunreachable-code.

#include <stdio.h>

int main()
{
  int var1 = (1 && 0);   /* does not warn */

  printf("var1 = %d\n", var1);  /* outputs: var1 = 0 */

  if ( 0 && 1 )
    printf("FIRST\n");   /* warns ok: printf unreachable */

  if ( 0 && (var1 == 10) )
    printf("SECOND\n");  /* warns ok: printf unreachable */

  if ( (var1 == 10) && (var1 == 20) )
    printf("THIRD\n");   /* does not warn */

  return 0;
}

Please do not expect a compilable testcase from me. 1) I don't know whether
this is a bug, 2) have no experience in gcc testcases.

I just tried to provide an idea.

With deep respect,

Vlada Macek


-- 

tuttle at sandbox dot cz changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Missing a warning: if-      |Missing a warning:
                   |condition is inherently     |inherently false expressions
                   |blocking the if-body        |
            Version|4.1.3                       |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35188