Support alternate attribute spelling __enable_if__

Attribute names usually support an alternate spelling that uses double
underscores before and after the attribute name, like e.g. attribute
((__aligned__)) for attribute ((aligned)). This is necessary to allow
use of attributes in system headers without polluting the name space.

However, for attribute ((enable_if)) that alternate spelling does not
work correctly. This is because of code in Parser::ParseGNUAttributeArgs
(ParseDecl.cpp) that specifically checks for the "enable_if" spelling
without allowing the alternate spelling.

Similar code in ParseDecl.cpp uses the normalizeAttrName helper to allow
both spellings. This patch adds use of that helper for the "enable_if"
check as well, which fixes attribute ((__enable_if__)).

Differential Revision: http://reviews.llvm.org/D11142

llvm-svn: 242029

1 files changed, 15 insertions, 0 deletions

diff --git a/clang/test/Sema/enable_if.c b/clang/test/Sema/enable_if.c
index 4644858593d..7faae43b577 100644
--- a/clang/test/Sema/enable_if.c
+++ b/clang/test/Sema/enable_if.c
@@ -77,6 +77,21 @@ void test3(int c) {
 #endif
 }
 
+// Verify that the alternate spelling __enable_if__ works as well.
+int isdigit2(int c) __attribute__((overloadable));  // expected-note{{candidate function}}
+int isdigit2(int c) __attribute__((overloadable))  // expected-note{{candidate function has been explicitly made unavailable}}
+  __attribute__((__enable_if__(c <= -1 || c > 255, "'c' must have the value of an unsigned char or EOF")))
+  __attribute__((unavailable("'c' must have the value of an unsigned char or EOF")));
+
+void test4(int c) {
+  isdigit2(c);
+  isdigit2(10);
+#ifndef CODEGEN
+  isdigit2(-10);  // expected-error{{call to unavailable function 'isdigit2': 'c' must have the value of an unsigned char or EOF}}
+#endif
+}
+
+
 #ifndef CODEGEN
 __attribute__((enable_if(n == 0, "chosen when 'n' is zero"))) void f1(int n); // expected-error{{use of undeclared identifier 'n'}}