[Bug c++/61867] New: gcc can't detect obviously false test

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61867

            Bug ID: 61867
           Summary: gcc can't detect obviously false test
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com

I just tried the following code on trunk 20140720

extern int g(int);

void f( int n)
{
    int i;

    i = g( n) & 0x02;

    if (i == 1)
        g( 2);
}

$ ~/gcc/results/bin/gcc -c -g -O2 -Wall -Wextra -pedantic -ansi jul21a.cc
$ 

so gcc has nothing to say about it. Here is cppcheck, a static analyser,
finding the problem

$ ~/cppcheck/trunk/cppcheck --enable=all jul21a.cc
Checking jul21a.cc...
[jul21a.cc:8] -> [jul21a.cc:10]: (style) Mismatching assignment and comparison, 
comparison 'i==1' is always false.
$

I note that about six bugs in the linux kernel and about 40 bugs in
Fedora Linux would be detected by implementing this fix.