From: Andy Gibbs <andyg1001@hotmail.co.uk>
Date: Sat, 17 Nov 2012 19:18:27 +0000 (+0000)
Subject: Prevent premature macro expansion in __has_builtin, __has_feature,
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=3f03b586351779be6947466f530f22c491b1b70f;p=clang

Prevent premature macro expansion in __has_builtin, __has_feature,
__has_attribute, __has_extension, making them behave more akin to
conventional macros.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@168268 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index 6baa593e78..1e77317d3e 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/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/test/Preprocessor/feature_tests.c b/test/Preprocessor/feature_tests.c
index b78a2517b1..19d80468ab 100644
--- a/test/Preprocessor/feature_tests.c
+++ b/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