[PATCH] D97362: [clang][parser] Allow attributes in explicit template instantiations

[Timm Bäder via Phabricator via cfe-commits]

tbaeder updated this revision to Diff 333510.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D97362/new/

https://reviews.llvm.org/D97362

Files:
  clang/include/clang/Parse/Parser.h
  clang/lib/Parse/ParseDecl.cpp
  clang/lib/Parse/ParseDeclCXX.cpp
  clang/test/Parser/cxx0x-attributes.cpp


Index: clang/test/Parser/cxx0x-attributes.cpp
===================================================================
--- clang/test/Parser/cxx0x-attributes.cpp
+++ clang/test/Parser/cxx0x-attributes.cpp
@@ -179,6 +179,7 @@
 struct [[]] Template<int> t; // expected-error {{an attribute list cannot appear here}}
 struct [[]] ::template Template<int> u; // expected-error {{an attribute list cannot appear here}}
 template struct [[]] Template<char>; // expected-error {{an attribute list cannot appear here}}
+template struct __attribute__((pure)) Template<std::size_t>; // We still allow GNU-style attributes here
 template <> struct [[]] Template<void>;
 
 enum [[]] E1 {};
Index: clang/lib/Parse/ParseDeclCXX.cpp
===================================================================
--- clang/lib/Parse/ParseDeclCXX.cpp
+++ clang/lib/Parse/ParseDeclCXX.cpp
@@ -1836,7 +1836,8 @@
     } else if (TemplateInfo.Kind == ParsedTemplateInfo::ExplicitInstantiation &&
         TUK == Sema::TUK_Declaration) {
       // This is an explicit instantiation of a class template.
-      ProhibitAttributes(attrs);
+      ProhibitCXX11Attributes(attrs, diag::err_attributes_not_allowed,
+                              /*DiagnoseEmptyAttrs=*/true);
 
       TagOrTempResult = Actions.ActOnExplicitInstantiation(
           getCurScope(), TemplateInfo.ExternLoc, TemplateInfo.TemplateLoc,
Index: clang/lib/Parse/ParseDecl.cpp
===================================================================
--- clang/lib/Parse/ParseDecl.cpp
+++ clang/lib/Parse/ParseDecl.cpp
@@ -1607,7 +1607,30 @@
 }
 
 void Parser::ProhibitCXX11Attributes(ParsedAttributesWithRange &Attrs,
-                                     unsigned DiagID) {
+                                     unsigned DiagID, bool DiagnoseEmptyAttrs) {
+
+  if (DiagnoseEmptyAttrs && Attrs.empty() && Attrs.Range.isValid()) {
+    // An attribute list has been parsed, but it was empty.
+    // This is the case for [[]].
+    const auto &LangOpts = getLangOpts();
+    auto &SM = PP.getSourceManager();
+    Token FirstLSquare;
+    Lexer::getRawToken(Attrs.Range.getBegin(), FirstLSquare, SM, LangOpts);
+
+    if (FirstLSquare.is(tok::l_square)) {
+      llvm::Optional<Token> SecondLSquare =
+          Lexer::findNextToken(FirstLSquare.getLocation(), SM, LangOpts);
+
+      if (SecondLSquare && SecondLSquare->is(tok::l_square)) {
+        // The attribute range starts with [[, but is empty. So this must
+        // be [[]], which we are supposed to diagnose because
+        // DiagnoseEmptyAttrs is true.
+        Diag(Attrs.Range.getBegin(), DiagID) << Attrs.Range;
+        return;
+      }
+    }
+  }
+
   for (const ParsedAttr &AL : Attrs) {
     if (!AL.isCXX11Attribute() && !AL.isC2xAttribute())
       continue;
Index: clang/include/clang/Parse/Parser.h
===================================================================
--- clang/include/clang/Parse/Parser.h
+++ clang/include/clang/Parse/Parser.h
@@ -2639,7 +2639,8 @@
   // which standard permits but we don't supported yet, for example, attributes
   // appertain to decl specifiers.
   void ProhibitCXX11Attributes(ParsedAttributesWithRange &Attrs,
-                               unsigned DiagID);
+                               unsigned DiagID,
+                               bool DiagnoseEmptyAttrs = false);
 
   /// Skip C++11 and C2x attributes and return the end location of the
   /// last one.


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