Clean up macros to detect underling C library functionality

[ldionne]

Summary

During the review of D50719, I said:

The presence/absence of C11 features in the underlying C library does not depend on what version of the C++ language we're compiling with.
The tests that use TEXT_HAS_C11_XXX should be updated to check TEST_STD_VER instead.

This does that.
The detection of C11 features happens no matter what the language level is.
The enabling/disabling of the C++ features is done based on the language level.

[mclow.lists]

include/__config

433

Should we be using __ISO_C_VISIBLE here, or __STDC_VERSION__?
I didn't change this, but ...

[ldionne]

include/__config

433

The weird part is that neither is defined when compiling C++ code..

[ldionne]

include/__config

433

This means that TEST_HAS_C11_FEATURES and _LIBCPP_HAS_C11_FEATURES will both be disabled all the time.

[ldionne]

Marking as "request changes" to get off my review queue until the problem I pointed w.r.t. TEST_HAS_C11_FEATURES and _LIBCPP_HAS_C11_FEATURES always being undefined is resolved.

[ldionne]

Is this still relevant? We don't have _LIBCPP_HAS_C11_FEATURES anymore. If not relevant, let's close this to clear up the queue.

[ldionne]

Commandeering to close as I don't think this applies anymore.

include/__config

 #define _LIBCPP_HAS_NO_VARIABLE_TEMPLATES
 #endif
 
-#if __ISO_C_VISIBLE >= 2011 || __cplusplus >= 201103L
+#if __ISO_C_VISIBLE >= 2011
 #  if defined(__FreeBSD__)
 #    define _LIBCPP_HAS_QUICK_EXIT
 #    define _LIBCPP_HAS_C11_FEATURES

include/cstdlib

 using ::wctomb;
 using ::mbstowcs;
 using ::wcstombs;
-#ifdef _LIBCPP_HAS_QUICK_EXIT
+#if !defined(_LIBCPP_CXX03_LANG) && defined(_LIBCPP_HAS_QUICK_EXIT)
 using ::at_quick_exit;
 using ::quick_exit;
 #endif
-#ifdef _LIBCPP_HAS_C11_FEATURES
+#if _LIBCPP_STD_VER > 14 && defined(_LIBCPP_HAS_C11_FEATURES)
 using ::aligned_alloc;
 #endif
 

test/std/language.support/support.start.term/quick_exit.pass.cpp

 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
-//
+// UNSUPPORTED: c++98, c++03
 
 // test quick_exit and at_quick_exit
 

test/std/language.support/support.start.term/quick_exit_check1.fail.cpp

 //
 //===----------------------------------------------------------------------===//
 //
+// UNSUPPORTED: c++98, c++03
 
 // test that referencing at_quick_exit when _LIBCPP_HAS_QUICK_EXIT is not defined
 // results in a compile error.

test/std/language.support/support.start.term/quick_exit_check2.fail.cpp

 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
-//
+// UNSUPPORTED: c++98, c++03
 
 // test that referencing quick_exit when _LIBCPP_HAS_QUICK_EXIT is not defined
 // results in a compile error.

test/support/test_macros.h

 
 // Sniff out to see if the underling C library has C11 features
 // Note that at this time (July 2018), MacOS X and iOS do NOT.
-#if __ISO_C_VISIBLE >= 2011 || TEST_STD_VER >= 11
+#if __ISO_C_VISIBLE >= 2011
 #  if defined(__FreeBSD__)
 #    define TEST_HAS_C11_FEATURES
 #  elif defined(__Fuchsia__)