From d41d09424487d386b780986a030d9915af4fdee1 Mon Sep 17 00:00:00 2001
From: Andy Gibbs <andyg1001@hotmail.co.uk>
Date: Sat, 17 Nov 2012 19:18:27 +0000
Subject: [PATCH] Prevent premature macro expansion in __has_builtin,
 __has_feature, __has_attribute, __has_extension, making them behave more akin
 to conventional macros.

llvm-svn: 168268
---
 clang/lib/Lex/PPMacroExpansion.cpp      |  6 +++---
 clang/test/Preprocessor/feature_tests.c | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 6baa593e788e..1e77317d3e0f 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1228,15 +1228,15 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
     IdentifierInfo *FeatureII = 0;
 
     // Read the '('.
-    Lex(Tok);
+    LexUnexpandedToken(Tok);
     if (Tok.is(tok::l_paren)) {
       // Read the identifier
-      Lex(Tok);
+      LexUnexpandedToken(Tok);
       if (Tok.is(tok::identifier) || Tok.is(tok::kw_const)) {
         FeatureII = Tok.getIdentifierInfo();
 
         // Read the ')'.
-        Lex(Tok);
+        LexUnexpandedToken(Tok);
         if (Tok.is(tok::r_paren))
           IsValid = true;
       }
diff --git a/clang/test/Preprocessor/feature_tests.c b/clang/test/Preprocessor/feature_tests.c
index b78a2517b18d..19d80468ab3f 100644
--- a/clang/test/Preprocessor/feature_tests.c
+++ b/clang/test/Preprocessor/feature_tests.c
@@ -32,3 +32,23 @@
     __has_builtin(__builtin_altivec_abs_v4sf)
 #error Broken handling of target-specific builtins
 #endif
+
+// Macro expansion does not occur in the parameter to __has_builtin,
+// __has_feature, etc. (as is also expected behaviour for ordinary
+// macros), so the following should not expand:
+
+#define MY_ALIAS_BUILTIN __c11_atomic_init
+#define MY_ALIAS_FEATURE attribute_overloadable
+
+#if __has_builtin(MY_ALIAS_BUILTIN) || __has_feature(MY_ALIAS_FEATURE)
+#error Alias expansion not allowed
+#endif
+
+// But deferring should expand:
+
+#define HAS_BUILTIN(X) __has_builtin(X)
+#define HAS_FEATURE(X) __has_feature(X)
+
+#if !HAS_BUILTIN(MY_ALIAS_BUILTIN) || !HAS_FEATURE(MY_ALIAS_FEATURE)
+#error Expansion should have occurred
+#endif