[PATCH] D11142: Support alternate attribute spelling __enable_if__

[Aaron Ballman]

On Mon, Jul 13, 2015 at 9:42 AM, Ulrich Weigand
<ulrich.weigand at de.ibm.com> wrote:
> uweigand created this revision.
> uweigand added reviewers: aaron.ballman, rsmith.
> uweigand added a subscriber: cfe-commits.
>
> 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__)).
>
>
> http://reviews.llvm.org/D11142
>
> Files:
>   lib/Parse/ParseDecl.cpp
>   test/Sema/enable_if.c
>
> Index: test/Sema/enable_if.c
> ===================================================================
> --- test/Sema/enable_if.c
> +++ test/Sema/enable_if.c
> @@ -77,6 +77,21 @@
>  #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'}}
>
> Index: lib/Parse/ParseDecl.cpp
> ===================================================================
> --- lib/Parse/ParseDecl.cpp
> +++ lib/Parse/ParseDecl.cpp
> @@ -365,7 +365,8 @@
>    // These may refer to the function arguments, but need to be parsed early to
>    // participate in determining whether it's a redeclaration.
>    std::unique_ptr<ParseScope> PrototypeScope;
> -  if (AttrName->isStr("enable_if") && D && D->isFunctionDeclarator()) {
> +  if (normalizeAttrName(AttrName->getName()) == "enable_if" &&
> +      D && D->isFunctionDeclarator()) {
>      DeclaratorChunk::FunctionTypeInfo FTI = D->getFunctionTypeInfo();
>      PrototypeScope.reset(new ParseScope(this, Scope::FunctionPrototypeScope |
>                                          Scope::FunctionDeclarationScope |


LGTM!

~Aaron