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boostorg / variant

Boost.org variant module
https://boost.org/libs/variant
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Ten tests from boost libraries failed to run after boost submodule variant updated from 7ecf72 to 0e122c #72

Closed spacelg closed 5 years ago

spacelg commented 5 years ago

Environment: VS 2017 + Windows Server 2016

Issue description: Ten tests from boost libraries failed to run after boost submodule variant updated from 7ecf72 to 0e122c boost/variant@1446f16. Could you please take a look?

Reproduce steps:

  1. git clone -c core.autocrlf=true --recursive ​https://github.com/boostorg/boost.git D:\Boost\src
  2. open a VS 2017 x64 command prompt and browse to D:\Boost\src
  3. .\bootstrap
  4. .\b2 headers variant=release --build-dir=..\out\x64rel address-model=64
  5. .\b2 variant=release --build-dir=..\out\x64rel address-model=64
  6. .\b2 -j4 variant=release --build-dir=..\out\x64rel libs\variant\test

log_x64_test_119.log

ErrorMessage: D:\Boost\src\boost\variant\detail\forced_return.hpp(43) : error C4716: <func:#1252 "??$forced_return@ABVtype_info@@@variant@detail@boost@@YAABVtype_info@@XZ"> 'boost::detail::variant::forced_return<type_info const &>': must return a value D:\Boost\src\boost\variant\detail\forced_return.hpp(43) : error C4716: <func:#1277 "??$forced_return@H@variant@detail@boost@@YAHXZ"> 'boost::detail::variant::forced_return': must return a value

apolukhin commented 5 years ago

Boost.Config needs develop to master merge to resolve the issue. In particular commit https://github.com/boostorg/config/commit/6231009e97daf0c501aa6d3a67688dcdfced2be5 should be merged to master.

apolukhin commented 5 years ago

@jzmaddock , could you please merge the https://github.com/boostorg/config/commit/6231009e97daf0c501aa6d3a67688dcdfced2be5 into the master of Boost.Config?

jzmaddock commented 5 years ago

Done.

However, shouldn't use of BOOST_UNREACHABLE_RETURN be a compiler-hint / warning suppression mechanism and not be dependent upon compiler magic which may or may not be present?

apolukhin commented 5 years ago

In boost::variant it is used as a warning suppression mechanism: https://github.com/boostorg/variant/blob/15a846fba0d52e8cb6b8e0459048df5b73c86706/include/boost/variant/detail/forced_return.hpp#L33-L43

Why it was causing hard failures without https://github.com/boostorg/config/commit/6231009e97daf0c501aa6d3a67688dcdfced2be5 is a good question. @jzmaddock probably we're misusing the macro, but there are usage limitations in the docs.