nvcc compiler warning; doctest.h(4138): warning : expression has no effect

[mojca]

Description

I've seen some claims that doctest shouldn't be throwing any warnings ;)

It does it for me, on the following two lines, when building from CMake in Release configuration under Visual Studio 2019 using the latest nvcc from CUDA 11.2:

_CrtSetReportMode(_CRT_ASSERT, prev_report_mode);
_CrtSetReportFile(_CRT_ASSERT, prev_report_file);

Full invocation (generated by CMake):

"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v11.2\bin\nvcc.exe" -gencode=arch=compute_52,code=\"compute_52,compute_52\" -gencode=arch=compute_52,code=\"sm_52,compute_52\" -gencode=arch=compute_60,code=\"compute_60,compute_60\" -gencode=arch=compute_60,code=\"sm_60,compute_60\" -gencode=arch=compute_61,code=\"compute_61,compute_61\" -gencode=arch=compute_61,code=\"sm_61,compute_61\" -gencode=arch=compute_75,code=\"compute_75,compute_75\" -gencode=arch=compute_75,code=\"sm_75,compute_75\" --use-local-env -ccbin "C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.28.29617\bin\HostX64\x64" -x cu   -I"D:\path\to\project" -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v11.2\include"     --keep-dir x64\Release  -maxrregcount=0  --machine 64 --compile -cudart static -std=c++14 -Xcompiler="/EHsc -Ob2"   -D_WINDOWS -DNDEBUG -DSOURCE_PATH_SIZE=38 -D"CMAKE_INTDIR=\"Release\"" -D"CMAKE_INTDIR=\"Release\"" -D_MBCS -Xcompiler "/EHsc /W1 /nologo /O2 /Fdtest_kernels.dir\Release\vc142.pdb /FS   /MD /GR" -o test_kernels.dir\Release\test_kernels.obj "D:\path\to\project\tests\test_kernels.cu"

Steps to reproduce

Add a simple cuda file (*.cu) to a CUDA-enabled CMake-based project and compile it. Inclusion of the header is sufficient to trigger the warning.

Extra information

• doctest version: v2.4.4
• Operating System: Windows 10
• Compiler+version: nvcc (Cuda compilation tools, release 11.2, V11.2.67)

PS: feel free to close this as invalid.

[onqtam]

Hello, and thanks for reporting this issue!

Can you paste the exact warning, as I don't have a CUDA compiler setup at hand? Does it happen only in Release?

And can you try putting a (void) cast in front of those 2 statements and let me know if that solves it for you? Thanks!

[mojca]

This is literally the complete warning (repeated a bunch of times):

C:\path\to\doctest.h(4138): warning : expression has no effect

Yes, this only happens with the release build. Some flags used with the release (incomplete list)

-Xcompiler="/EHsc -Ob2" -DNDEBUG -D_MBCS -Xcompiler "/EHsc /W1 /nologo /O2 /FS   /MD /GR"

some flags used with the debug configuration:

-Xcompiler="/EHsc -Zi -Ob0" -g -D_MBCS -Xcompiler "/EHsc /W1 /nologo /Od /FS /Zi /RTC1 /MDd /GR"

Yes, using (void) as in

(void)_CrtSetReportMode(_CRT_ASSERT, prev_report_mode);
(void)_CrtSetReportFile(_CRT_ASSERT, prev_report_file);

helps.

[onqtam]

I pushed a fix for this in the dev branch - will release a new version in the next couple of weeks!