[Bug c/18128] New: REGRESSION: Wrong precedence

[adamm at zombino dot com]

Produces wrong code on both 3.3.4 and 3.4.2 (in Debian Sid). It works perfectly
with gcc 2.95.

The problem is that,
-A+B == B-A
-A()+B == B-A()
-A+B() == B()-A
but,
-A()+B() ?= B()-A()

if A or B depend on each other, the last condition is !=. Otherwise, it is ==.
This breaks any code that relies on things like stack to execute operations, for
example,

stack<int> A;
A.push(5);
A.push(2);

// do a subtraction of 5-2 and push resuls onto stack
A.push( -A.pop() + A.pop());

What it does, it actually A.pop() - A.pop() which is very wrong.



>>>>>>>>>>>>>  TEST CASE >>>>>>>>>>>>>>>>>>>>>>>>>
#include <stdio.h>

double A(){
        static int div;
        double r = 10.0/++div+div;
        printf( "A() returns: %f iteration %d\n", r, div );
        return r;
}

int main()
{
        /* EXECUTES A()-A() INSTEAD OF -A()+A() */
        printf( "-4.0 is %f\n", -A() + A());
}
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

reported in Debian BTS: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=278081

-- 
           Summary: REGRESSION: Wrong precedence
           Product: gcc
           Version: 3.3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: adamm at zombino dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-linux
  GCC host triplet: i386-linux
GCC target triplet: i386-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18128