[Bug c/60036] New: Spurious signedness conversion warning with relational operator

[chengniansun at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60036

            Bug ID: 60036
           Summary: Spurious signedness conversion warning with relational
                    operator
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chengniansun at gmail dot com

Gcc-trunk emits a signedness conversion warning for the statement "f ^= fn1() >
a;". However, as the value of "fn1() > a" is either 1 or 0, the warning is not
true. 

Moreover, Gcc-4.8 and 4.7 do not output this warning. And if I change the
statement to "f = f ^ (fn1() > a);", gcc-trunk does not emit this warning,
either.



$: cat conversion-for-boolean.c
extern int fn1();
unsigned fn(int a) {
  unsigned f = 9;
  f ^= fn1() > a;
  return f;
}

$: gcc-trunk -c -Wconversion -std=c11 conversion-for-boolean.c
conversion-for-boolean.c: In function ‘fn’:
conversion-for-boolean.c:4:5: warning: conversion to ‘unsigned int’ from ‘int’
may change the sign of the result [-Wsign-conversion]
   f ^= fn1() > a;
     ^
$: gcc-4.8 -c -Wconversion -std=c11 conversion-for-boolean.c
$: gcc-4.7 -c -Wconversion -std=c11 conversion-for-boolean.c
$: gcc-trunk --version
gcc-trunk (GCC) 4.9.0 20140131 (experimental)
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.