Catch2 not fully compliant with c++17

[tdegeus]

I'm trying to upgrade the conda-forge feedstock to the latest release (https://github.com/conda-forge/catch2-feedstock/pull/33 ). However, I'm getting a build error:

../include/internal/catch_uncaught_exceptions.cpp: In function 'bool Catch::uncaught_exceptions()':
1023../include/internal/catch_uncaught_exceptions.cpp:20:21: error: 'bool std::uncaught_exception()' is deprecated [-Werror=deprecated-declarations]
1024         return std::uncaught_exception();
1025                     ^~~~~~~~~~~~~~~~~~
1026In file included from ../include/internal/catch_uncaught_exceptions.cpp:11:
1027$BUILD_PREFIX/powerpc64le-conda-linux-gnu/include/c++/8.4.0/exception:102:8: note: declared here
1028   bool uncaught_exception() _GLIBCXX_USE_NOEXCEPT __attribute__ ((__pure__));
1029        ^~~~~~~~~~~~~~~~~~
1030../include/internal/catch_uncaught_exceptions.cpp:20:40: error: 'bool std::uncaught_exception()' is deprecated [-Werror=deprecated-declarations]
1031         return std::uncaught_exception();
1032                                        ^
1033In file included from ../include/internal/catch_uncaught_exceptions.cpp:11:
1034$BUILD_PREFIX/powerpc64le-conda-linux-gnu/include/c++/8.4.0/exception:102:8: note: declared here
1035   bool uncaught_exception() _GLIBCXX_USE_NOEXCEPT __attribute__ ((__pure__));
1036        ^~~~~~~~~~~~~~~~~~
1037../include/internal/catch_uncaught_exceptions.cpp:20:40: error: 'bool std::uncaught_exception()' is deprecated [-Werror=deprecated-declarations]
1038         return std::uncaught_exception();
1039                                        ^
1040In file included from ../include/internal/catch_uncaught_exceptions.cpp:11:
1041$BUILD_PREFIX/powerpc64le-conda-linux-gnu/include/c++/8.4.0/exception:102:8: note: declared here
1042   bool uncaught_exception() _GLIBCXX_USE_NOEXCEPT __attribute__ ((__pure__));
1043        ^~~~~~~~~~~~~~~~~~
1044cc1plus: all warnings being treated as errors

[mjscosta]

Adding full build log:
https://travis-ci.org/github/conda-forge/catch2-feedstock/builds/725973219

Check here, Catch2 seems not be completely compliant with c++17:
https://travis-ci.org/github/conda-forge/catch2-feedstock/builds/725973219#L1018

resulting on the error posted by tdgeus.

Please advise, is Catch2 intended to be strict compliant with c++17?

[mjscosta]

Hi @tdegeus, could you change the issue name to something like: "Catch2 not fully compliant with c++17 causing tests to fail", I cannot since I'm not the author of the issue.

Thanks, Best.

[mjscosta]

Adding reference to conda-forge issue:
https://github.com/conda-forge/catch2-feedstock/issues/32

[mjscosta]

The error seems to be related to the gcc version,

In the ppc environment the gcc version is 8.4
https://api.travis-ci.org/v3/job/726135670/log.txt

In the linux version the gcc version is 7.5
https://dev.azure.com/conda-forge/84710dde-1620-425b-80d0-4cf5baca359d/_apis/build/builds/207695/logs/17

According to https://en.cppreference.com/w/cpp/error/uncaught_exception, is deprecated in c++17, and gcc 8.4 already implemented the deprecation warning.

Since testes are running with option
// Enable all warnings as errors
CATCH_ENABLE_WERROR:BOOL=ON
This results in failed tests when using gcc 8.4

[horenmar]

Right, so the problem is that the detection of stdlib's support for std::uncaught_exceptions is not firing, even though the stdlib has deprecated std::uncaught_exception, and thus we can surmise that std::uncaught_exceptions is indeed supported.

I _think_ I know why it misfires, and how to fix it, but it will have to wait until I have the time.

[giellamo]

@mjscosta Am I wrong or using deprecated things is allowed by the standard?? So even if you use a deprecated thing you are compliant.

[mjscosta]

I'm not sure it is an issue regarding the standard or not, the issue I've got was on running the tests for Catch2, and the tests started to fail when using updated compiler (gcc 8.4), where the combination CATCH_ENABLE_WERROR:BOOL=ON (default as ON on the cmake), resulted on the tests failing.

I've fixed the issue by setting the option to OFF for packaging purposes. So the issue maybe should be addressed regarding the tests, as they will start to fail when you update the compiler to one fully supporting c++17, at least for gcc 8.4 >= .

[mjscosta]

Checking the builds, it seems that when executing the tests for COMPILER='g++-8' (https://travis-ci.org/github/catchorg/Catch2/jobs/726786262)
, the compiler version displayed on the job is 5.04:
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.12) 5.4.0 20160609

[horenmar]

@mjscosta https://travis-ci.org/github/catchorg/Catch2/jobs/726786262#L387

@giellamo It is indeed allowed, just not recommended. Ironically we (wg21) still haven't figured out whether deprecated means "will be removed at some point", or just "you really shouldn't use this".

[mjscosta]

https://en.cppreference.com/w/cpp/language/attributes/deprecated and according to https://en.cppreference.com/w/cpp/error/uncaught_exception, it will be removed in c++20.

@horenmar any idea why the error its occurring in the conda-forge packaging ?

[horenmar]

Should be fixed in master.