Warning for parentheses around comparison in operand of ‘==’

[barsan-md]

I know this was reported many times and maybe fixed (at least for gcc 4.7) but I'm gaving this issue with GCC 6.3 on Linux Mint 18.

Anyway a temporary solution that works for me is to add
#pragma GCC diagnostic ignored "-Wparentheses"
in the source code

[horenmar]

We are currently attempting to suppress the warning by using _Pragma for GCC versions 4.8 and newer.

This would let us suppress it only for the assertion macros, but as it turns out, GCC likely has a long-standing bug in handling _Pragmas in C++ mode, as can be seen in this example

#include <stdio.h>

#define TEST(expr) \
    int a = 1; \
    _Pragma( "GCC diagnostic push" ) \
    _Pragma( "GCC diagnostic ignored \"-Wparentheses\"" ) \
    if (a <= expr) { \
        printf("filler\n"); \
    } \
    _Pragma( "GCC diagnostic pop" )

int main(){
    int b = 2, c = 3;
    TEST(b == c);
}

If you compile this using current GCC as C, it will not trigger the warning. If you compile this as C++, it will warn about bad parentheses.

We will likely end-up using plain pragma to suppress the warning globally in the next release.

[onqtam]

I have the same experience in doctest with _Pragma() not working for the g++ frontend - related reports:

• https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55578
• https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69543

It's weird that I don't get the -Wparentheses warning though - but my expression decomposition uses operator<< (like lest does) instead of operator<= so it might be related to operator precedence - << is before the comparison ones

[aldanor]

Same for me (GCC 5.2).

In my case, enabling CATCH_CONFIG_FAST_COMPILE upgrading to Catch v1.8.2 triggers a bajillion of -Wparentheses warnings that weren't there in the normal mode, and the build is in fact slower.

(there were also a few of these spurious warnings with 1.7.2 version that I had to wrap in parens manually -- I couldn't figure out the logic behind those)

[aldanor]

Related: #565

[horenmar]

@aldanor Basically, at some point in the past (can't tell you version on top of my head, but a recent one), we switched to using _Pragmas for GCC that support them and only using #pragma for older ones. As it turns out, the _Pragma support in GCC is very spotty: I can compile a small Catch example file using g++-4.8 on my machine without warnings, but on different machine, with newer g++, the warnings come back. Also it has trouble with templates...

We will probably end up just using #pragma for all gcc versions and let it leak into the test files.

[horenmar]

I am going to close this, as I moved Catch back to force disabling Wparentheses everywhere using #pragma in 8f85d08.

This means that we disable the warning for GCC users even outside our assertions, but the spotty _Pragma support meant that the status quo was untenable.