[Bug c++/105278] New: no warning for precise literals compared with floats

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105278

            Bug ID: 105278
           Summary: no warning for precise literals compared with floats
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com
  Target Milestone: ---

For this C++ code:

extern void g( int);

void f( float a)
{
        if (a == 0.1234)
                g( 1);
}

recent gcc trunk has nothing to say:

$ /home/dcb/gcc/results/bin/gcc -c -g -O2 -Wall -Wextra -pedantic apr14b.cc
$ 

Here is clang finding the problem:

$ /home/dcb/llvm/results/bin/clang -c -g -O2 -Wall   apr14b.cc
apr14b.cc:6:8: warning: floating-point comparison is always false; constant
cannot be represented exactly in type 'float' [-Wliteral-range]
        if (a == 0.1234)
            ~ ^  ~~~~~~~~~~~
1 warning generated.

Interestingly, if float is replaced by double, the warning goes away.