Building on OS X 10.8

[martin....@gmx.net]

Hi!

I've got some trouble trying to get emsdk installed on Mac OS X 10.8.5. At first the clang build it complains about

Host Clang must be able to find libstdc++4.7 or newer!

I've found a Japanese article which apparently suggests adding -DLLVM_ENABLE_LIBCXX=ON to the CMake argument list.
With that, clang got compiled but emscripten itself now fails:

…/emscripten/master/tools/optimizer/simple_ast.h:15:10: fatal error: 
      'unordered_set' file not found
#include <unordered_set>
         ^

This sounds like issue #2997 so perhaps the changes made there can be extended somewhat.
In particular, you could provide some way in which the user can supply a compiler command name in the environment, so that I could try out alternatives, e.g. the `clang++-mp-3.7` I can install using MacPorts.

Should I file bug reports for any of this?

[Jukka Jylänki]

If you use the default system Clang that you have there, and write a small test application that includes unordered_set, does that work, or does it fail in the same manner? (Remember to compiled with -std=c++11)

emsdk uses CMake to configure the builds of the compiler and the native optimizer, and it does not use anything special to pick the compiler on non-Windows, so you should be able to use CMake-specific means to specify the compiler to be used. See e.g. here: http://www.cmake.org/Wiki/CMake_FAQ#Method_1:_use_environment_variables . Haven't tested, but I expect that should work on non-Windows systems.

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[martin....@gmx.net]

On Wednesday, June 10, 2015 at 5:13:29 PM UTC+2, jj wrote:

If you use the default system Clang that you have there, and write a small test application that includes unordered_set, does that work, or does it fail in the same manner? (Remember to compiled with -std=c++11)

It fails in the same way. It even fails if I use clang++-mp-3.7 from MacPorts, see http://stackoverflow.com/q/30757580/1468366 for details.

On the other hand, it succeeds if I also pass -stdlib=libc++ on the command line. And indeed, a plain vanilla emsdk can build both clang and emscripten if I have CXXFLAGS=-stdlib=libc++ in the environment. Apparently without any need for MacPorts at all (except perhaps for git). Perhaps you should always include that setting for OS X? Or at least document it somewhere?

[chronotext]

The problem described here sounds like a known XCode issue to me:

If you want to build C++11 code with a "recent" SDK (e.g. MacOSX10.10.sdk) while keeping an older deployment-target:

It is not enough to pass "-mmacosx-version-min" in the CXX_FLAGS

The solution is to pass "-stdlib" as well, e.g.

"-mmacosx-version-min=10.8 -stdlib=libc++"

HTH,

Ariel

[Jukka Jylänki]

Thanks, I authored this commit to assist in this issue: https://github.com/juj/emsdk/commit/bc56d6eee02b637c96a18127e4f58e5476b2a885 . Tested building on my OS X 10.10.2, and there it looked safe to keep that flag in the build at all times, so I think that should be good to do unconditionally.

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