Re: [boost] Strange libstdc++ versions in travis-ci testers

On Fri, 29 Jun 2018 at 03:56, Rene Rivera via Boost wrote:

On Thu, Jun 28, 2018 at 9:11 PM Peter Dimov via Boost wrote:

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Rene Rivera wrote:

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On Thu, Jun 28, 2018 at 4:40 PM Peter Dimov via Boost wrote:

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To detect the actual libstdc++ version, you should use the Boost.Config macro, as it's generally more reliable.

Why is it more reliable?

__GLIBCXX__ is a date, which is not very useful for determining the version.

Which is what Predef uses. And also uses __GLIBCPP__ as fallback. But, yes they are dates, as that's the only real indicator of *only* libstdc++ I knew of.

There's _GLIBCXX_RELEASE but that's only for 7 and up. Config uses

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Hm, hadn't kept up on that. I'll have to add that if available.

See https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_macros.html which also has a link to https://gcc.gnu.org/onlinedocs/libstdc++/manual/abi.html#abi.versioning.__GL... explaining why the __GLIBCXX__ and __GLIBCPP__ macros are useless for determining the version.

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__has_include to detect the version under Clang,

How would __has_include help?

By checking for the presence of a header that was added in a particular version. If is available, you're using at least GCC 4.9

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__GNUC__ under g++.

But that's the g++ version, not the lib version.

When you're using g++ the lib version *is* the g++ version. Using older or newer versions of libstdc++ with g++ is not supported, you have to use the bundled one. So when compiling with g++ the compiler version and the library version are the same.