Fix preprocessor checks for Clang builtins

Clang seems to define built-ins that start with "__builtin_" as
non-keywords, which means that we need to use __has_builtin to detect
them, not __is_identifier. The built-ins that don't start with
"__builtin_" are keywords, and can only be detected using
__is_identifier and not by __has_builtin.

Backport from mainline
2019-07-02  Jonathan Wakely  <jwakely@redhat.com>

	* include/bits/c++config (_GLIBCXX_HAVE_BUILTIN_LAUNDER)
	(_GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED): Use __has_builtin
	instead of __is_identifier to detect Clang support.

From-SVN: r273832

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 1c6e5592bf45fba6d109167590c6599a16d36db5..d60df1790cdc54a1a62f585ae6fa2e448a481a6b 100644 (file)
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,12 @@
+2019-07-26  Jonathan Wakely  <jwakely@redhat.com>
+
+       Backport from mainline
+       2019-07-02  Jonathan Wakely  <jwakely@redhat.com>
+
+       * include/bits/c++config (_GLIBCXX_HAVE_BUILTIN_LAUNDER)
+       (_GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED): Use __has_builtin
+       instead of __is_identifier to detect Clang support.
+
 2019-07-26  Jonathan Wakely  <jwakely@redhat.com>
 
        Backport from mainline