[Bug c++/60342] New: -Wsign-conversion ignores explicit conversion

[woodroof at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60342

            Bug ID: 60342
           Summary: -Wsign-conversion ignores explicit conversion
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: woodroof at gmail dot com

Simple example:
#include <cstddef>
#include <limits>

int main()
{
        int int_value;
        if (std::numeric_limits<size_t>::max() -
static_cast<size_t>(int_value))
        {
        }
}

Result:
1.cpp: In function ‘int main()’:
1.cpp:7:72: warning: conversion to ‘long unsigned int’ from ‘int’ may change
the sign of the result [-Wsign-conversion]
  if (std::numeric_limits<size_t>::max() - static_cast<size_t>(int_value))
                                                                        ^

If I change numeric_limits::max to any size_t variable, warning will not be
generated. There is no warning also if I used usigned instead of size_t.

Possible the same problem as in bug 49626, but there is no conversion to a
wider type.