[PATCH] D19344: [libc++] fix constexpr error when build with MUSL and macro redef warning when no exception

[Weiming Zhao via cfe-commits]

weimingz added inline comments.

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Comment at: include/__config:300
@@ -299,3 +299,3 @@
 
-#if !(__has_feature(cxx_exceptions))
+#if !(__has_feature(cxx_exceptions)) && !defined(_LIBCPP_NO_EXCEPTIONS)
 #define _LIBCPP_NO_EXCEPTIONS
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Is this change OK?

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Comment at: include/__mutex_base:43
@@ -42,3 +42,3 @@
     _LIBCPP_INLINE_VISIBILITY
-#ifndef _LIBCPP_HAS_NO_CONSTEXPR
+#ifndef _LIBCPP_HAS_NO_CXX14_CONSTEXPR
      constexpr mutex() _NOEXCEPT : __m_(PTHREAD_MUTEX_INITIALIZER) {}
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EricWF wrote:
> This is not OK. It's critical that mutex have a constexpr constructor that it runs during the "Constant initialization" phase of static initialization.
> Heres an example of the difference this makes: https://godbolt.org/g/3cvlMJ
> 
> Also the constructor is specified as being constexpr in C++11. We can't turn that off. 
> 
> If one particular pthread implementation is broken then we need a fix targeted to only that implementation.  However this seems like a pthread bug and not a libc++ bug.
The macro has an "#else" part.  I'm not familiar with this, but it seems the constexpr an "optional feature".





http://reviews.llvm.org/D19344