libc++ assumed to be required for C++11 support when using Clang

[doraskayo]

libstdc++ is the default STL implementation in Linux (at least in most distributions), and provides full support for C++11 (and C++14). However, GLM assumes that it doesn't have C++11 support when compiled using Clang with anything but libc++. This is a wrong assumption to make, and breaks the build for no actual reason on Linux.

[Groovounet]

GLM is just being conservative. Are you aware of a way to detect the C++ version of the STL implementation? I have been looking for one for exactly this purpose...

[doraskayo]

I guess it may be possible to check for it, but as far as I know, there is no single universally-supported be-all end-all solution. If you really need to check for it, the only way would probably be to do the exact same thing you're already doing; just keep iterating on it until nobody complains.

As for Clang, the solution linked above seems to be reliable since this commit (May 2012) for both -std=c++11 and -std=gnu++11 (it only worked for -std=c++11 before that commit.) So at the very least it can be relied upon to check for C++11 support in Clang compilers from the last 4 years.

In general, the best way to deal with such an issue is to first check the most "promising" heuristic, and keep falling back to lesser heuristics until you end up deciding that it does not fit the bill. That way you can minimize the chance of failure to such a low rate that nobody notices it.

[Groovounet]

Erm, I think GLM does a good job at C++11 checking https://github.com/g-truc/glm/blob/0.9.8.3/glm/detail/setup.hpp#L170 but yes the STL implementation version is independent from compiler version.
I found the approached you pointed out https://github.com/g-truc/glm/blob/0.9.8.3/glm/detail/setup.hpp#L301-L302 for libc++ but nothing for libstdc++

You can use GLM_LANG_STL11_FORCED to force GLM to consider that the STL implementation is a C++11 one.

Thanks,
Christophe

[doraskayo]

@Groovounet, as far as I can tell, defining GLM_LANG_STL11_FORCED will not help in this case. It only affects the Android case.

[Groovounet]

I had a second look and turns out I was wrong. \o/
GLM_FORCE_CXX11 should be used and now it's going to be taken into account for Clang outside Android as well.

Thanks for contributing,
Christophe