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Date: Tue, 02 Feb 2010 10:10:00 -0000
Subject: [Bug c/42935]  New: Warning "u64 = u32 * u32;" - i.e. not casting one u32 to u64
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From: "etienne_lorrain at yahoo dot fr" <gcc-bugzilla@gcc.gnu.org>
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It is a beginer bug, but it would be nice to get a warning in:

#include <stdio.h>
unsigned val1 = 0x10000000, val2 = 0x100;
int main(int argc, char **argv)
{
    unsigned long long val3 = val1 * val2;
    printf ("val1 = 0x%X, val2 = 0x%X, val3 = 0x%llX, val1*val2 = 0x%llX\n",
        val1, val2, val3, (unsigned long long)(val1*val2));
}

Obviously the line printed is:
val1 = 0x10000000, val2 = 0x100, val3 = 0x0, val1*val2 = 0x0
(compiled with "gcc -w -Wall -O2 tmp.c" you get no warning)
Got bitten yesterday by gcc-4.4.3, reproduced today on gcc version 4.1.2.


-- 
           Summary: Warning "u64 = u32 * u32;" - i.e. not casting one u32 to
                    u64
           Product: gcc
           Version: 4.4.3
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: etienne_lorrain at yahoo dot fr
 GCC build triplet: i686-pc-cygwin
  GCC host triplet: i686-pc-cygwin
GCC target triplet: i686-pc-cygwin


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42935