From 46a92fd8a436d59e85d8a7fad508c3ca6c60e204 Mon Sep 17 00:00:00 2001
From: Krystian Stasiowski <sdkrystian@gmail.com>
Date: Sun, 2 Feb 2020 11:53:21 -0500
Subject: [PATCH] Guard __has_builtin

---
 include/boost/static_string/config.hpp        | 16 +++++++++++++---
 include/boost/static_string/static_string.hpp |  2 +-
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/boost/static_string/config.hpp b/include/boost/static_string/config.hpp
index 3d12242..7d681ba 100644
--- a/include/boost/static_string/config.hpp
+++ b/include/boost/static_string/config.hpp
@@ -32,11 +32,18 @@
 #endif
 #endif
 
+// Can we use __has_builtin?
+#ifdef __has_builtin
+#define BOOST_STATIC_STRING_HAS_BUILTIN(arg) __has_builtin(arg)
+#else
+#define BOOST_STATIC_STRING_HAS_BUILTIN(arg) 0
+#endif
+
 // Can we use is_constant_evaluated?
 // Standard version
 #if __cpp_lib_is_constant_evaluated >= 201811L
 #define BOOST_STATIC_STRING_IS_CONST_EVAL std::is_constant_evaluated()
-#elif defined(__clang__) && __has_builtin(__builtin_is_constant_evaluated)
+#elif defined(__clang__) && BOOST_STATIC_STRING_HAS_BUILTIN(__builtin_is_constant_evaluated)
 // If we have clang version 9+, we can use the intrinsic
 // While gcc also has this, we don't need it
 #define BOOST_STATIC_STRING_IS_CONST_EVAL __builtin_is_constant_evaluated()
@@ -53,6 +60,7 @@
 #define BOOST_STATIC_STRING_NODISCARD
 #endif
 
+
 // MSVC doesn't define __cplusplus by default
 #ifdef _MSVC_LANG
 #define BOOST_STATIC_STRING_STANDARD_VERSION _MSVC_LANG
@@ -160,11 +168,13 @@ defined(__clang__) && \
 // that cannot use the library comparison function
 // objects at all in constant expresssions. In these
 // cases, we use whatever will make more constexpr work.
-#if defined(__clang__) && defined(__GLIBCXX__) && ((__GLIBCXX__ > 20181206 && __GLIBCXX__ <= 20190812))
+#if defined(__clang__) 
+#if defined(__GLIBCXX__) && ((__GLIBCXX__ > 20181206 && __GLIBCXX__ <= 20190812))
 #define BOOST_STATIC_STRING_NO_PTR_COMP_FUNCTIONS
-#elif __has_builtin(__builtin_constant_p) || defined(BOOST_STATIC_STRING_IS_CONST_EVAL)
+#elif BOOST_STATIC_STRING_HAS_BUILTIN(__builtin_constant_p) || defined(BOOST_STATIC_STRING_IS_CONST_EVAL)
 #define BOOST_STATIC_STRING_NO_PTR_COMP_FUNCTIONS
 #endif
+#endif
 
 namespace boost {
 namespace static_string {
diff --git a/include/boost/static_string/static_string.hpp b/include/boost/static_string/static_string.hpp
index ad152a6..6711049 100644
--- a/include/boost/static_string/static_string.hpp
+++ b/include/boost/static_string/static_string.hpp
@@ -627,7 +627,7 @@ is_inside(
         return true;
     return false;
   }
-#elif defined(__clang__) && __has_builtin(__builtin_constant_p)
+#elif defined(__clang__) && BOOST_STATIC_STRING_HAS_BUILTIN(__builtin_constant_p)
   // We can also try using __builtin_constant_p
   if (__builtin_constant_p((ptr, src_first, src_last)))
   {