Suppress NVCC unused variable warnings

[ahans]

Description

This defines CATCH_INTERNAL_START_WARNINGS_SUPPRESSION and CATCH_INTERNAL_STOP_WARNINGS_SUPPRESSION when compiled with nvcc to suppress warnings about unused variables.

GitHub Issues

#2306

[codecov]

Codecov Report

Merging #2427 (524c516) into devel (605a347) will increase coverage by 0.08%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##            devel    #2427      +/-   ##
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+ Coverage   91.43%   91.51%   +0.08%     
==========================================
  Files         159      159              
  Lines        7501     7501              
==========================================
+ Hits         6858     6864       +6     
+ Misses        643      637       -6     

[horenmar]

So, this would work, but wouldn't properly slot into how the macros are used across Catch2. If I am reading the docs correctly, then the correct approach would be something like this

Suggested change

	# define CATCH_INTERNAL_START_WARNINGS_SUPPRESSION _Pragma( "nv_diag_suppress 177" )
	# define CATCH_INTERNAL_STOP_WARNINGS_SUPPRESSION _Pragma( "nv_diag_default 177" )
	# define CATCH_INTERNAL_START_WARNINGS_SUPPRESSION _Pragma( "nv_diagnostic push" )
	# define CATCH_INTERNAL_STOP_WARNINGS_SUPPRESSION _Pragma( "nv_diagnostic pop" )
	# define CATCH_INTERNAL_SUPPRESS_UNUSED_VARIABLE_WARNINGS _Pragma ( "nv_diag_suppress 177" )

[ahans]

Thanks for your comment! Unfortunately, your suggestion makes the warnings come back. The reason is that in the place where the "unused" variables are introduced we do not use CATCH_INTERNAL_SUPPRESS_UNUSED_VARIABLE_WARNINGS, but CATCH_INTERNAL_SUPPRESS_GLOBALS_WARNINGS. Apparently, other compilers than nvcc would emit a different warning here. I see two solutions to this:

1. Define CATCH_INTERNAL_SUPPRESS_GLOBALS_WARNINGS with the suppression of 177 instead of CATCH_INTERNAL_SUPPRESS_UNUSED_VARIABLE_WARNINGS.
2. Leave the #defines as you suggested and add CATCH_INTERNAL_SUPPRESS_UNUSED_VARIABLE_WARNINGS to the macros in catch_test_registry.hpp that introduce the variables nvcc complains about.

I updated my PR to implement option 2), since I think that is the cleaner approach. After all, nvcc's warning is about a variable that is "declared but never referenced" and nothing related to global variables. Let me know what you think!

[horenmar]

2. is the right solution, but it might be worth it to open up a bug upstream that a type with opaque constructor triggers unused variable warning. Usually compilers don't warn on this, because they assume that the opaque constructor contains side-effects that the user cares for.