aaron.ballman created this revision.
aaron.ballman added reviewers: rsmith, dblaikie, echristo.
Herald added a subscriber: krytarowski.
GCC is currently considering a patch to accept `__gnu__` as a scoped attribute
namespace that aliases to `gnu`. This is useful for libstdc++ so that they
don't have to worry about stepping on the user's namespace. The GCC bug can be
found at: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86288
This patch supports parsing `__gnu__`, but it does support `__clang__`
similarly because `__clang__` is a predefined macro that expands to an empty
expansion. In order to support `[[__clang__::foobar]]` as an attribute
spelling, I think we'd need to introduce some frontend hacks. Rather than get
bogged down in that support, I am proposing to support only `__gnu__` for the
moment, to ensure we remain compatible with libstdc++ when it makes the switch
to the new attribute namespace.
Btw, an alternative implementation strategy here would be to make the `GCC`
spelling introduce both the `gnu` and `__gnu__` variants of the attribute in
addition to the GNU-style spelling. We have no CXX11 spellings that manually
specify `gnu` as the vendor namespace, so this would suffice, but it feels a
bit more fragile than baking this into the attribute system directly.
https://reviews.llvm.org/D53591
Files:
include/clang/Sema/ParsedAttr.h
lib/Basic/Attributes.cpp
lib/Parse/ParseDeclCXX.cpp
lib/Sema/ParsedAttr.cpp
lib/Sema/SemaDeclAttr.cpp
lib/Sema/SemaType.cpp
test/Preprocessor/has_attribute.cpp
test/SemaCXX/attr-gnu.cpp
utils/TableGen/ClangAttrEmitter.cpp
Index: utils/TableGen/ClangAttrEmitter.cpp
===================================================================
--- utils/TableGen/ClangAttrEmitter.cpp
+++ utils/TableGen/ClangAttrEmitter.cpp
@@ -2935,9 +2935,9 @@
if (I != List.cbegin())
OS << " else ";
if (I->first.empty())
- OS << "if (!Scope || Scope->getName() == \"\") {\n";
+ OS << "if (ScopeName == \"\") {\n";
else
- OS << "if (Scope->getName() == \"" << I->first << "\") {\n";
+ OS << "if (ScopeName == \"" << I->first << "\") {\n";
OS << " return llvm::StringSwitch<int>(Name)\n";
GenerateHasAttrSpellingStringSwitch(I->second, OS, Spelling, I->first);
OS << "}";
Index: test/SemaCXX/attr-gnu.cpp
===================================================================
--- test/SemaCXX/attr-gnu.cpp
+++ test/SemaCXX/attr-gnu.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -std=gnu++11 -fsyntax-only -fms-compatibility -verify %s
+// RUN: %clang_cc1 -std=gnu++17 -fsyntax-only -fms-compatibility -verify %s
void f() {
// GNU-style attributes are prohibited in this position.
@@ -43,3 +43,10 @@
tuTest1(x); // expected-error {{no matching function for call to 'tuTest1'}}
tuTest2(x); // expected-error {{no matching function for call to 'tuTest2'}}
}
+
+[[gnu::__const__]] int f2() { return 12; }
+[[__gnu__::__const__]] int f3() { return 12; }
+[[using __gnu__ : __const__]] int f4() { return 12; }
+
+static_assert(__has_cpp_attribute(gnu::__const__));
+static_assert(__has_cpp_attribute(__gnu__::__const__));
Index: test/Preprocessor/has_attribute.cpp
===================================================================
--- test/Preprocessor/has_attribute.cpp
+++ test/Preprocessor/has_attribute.cpp
@@ -21,11 +21,15 @@
int has_clang_fallthrough_2();
#endif
-// The scope cannot be bracketed with double underscores.
+// The scope cannot be bracketed with double underscores unless it is for gnu.
// CHECK: does_not_have___clang___fallthrough
#if !__has_cpp_attribute(__clang__::fallthrough)
int does_not_have___clang___fallthrough();
#endif
+// CHECK: has_gnu_const
+#if __has_cpp_attribute(__gnu__::__const__)
+ int has_gnu_const();
+#endif
// Test that C++11, target-specific attributes behave properly.
Index: lib/Sema/SemaType.cpp
===================================================================
--- lib/Sema/SemaType.cpp
+++ lib/Sema/SemaType.cpp
@@ -7273,7 +7273,7 @@
// not appertain to a DeclaratorChunk. If we handle them as type
// attributes, accept them in that position and diagnose the GCC
// incompatibility.
- if (attr.getScopeName() && attr.getScopeName()->isStr("gnu")) {
+ if (attr.isGNUScope()) {
bool IsTypeAttr = attr.isTypeAttr();
if (TAL == TAL_DeclChunk) {
state.getSema().Diag(attr.getLoc(),
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -5834,10 +5834,8 @@
!S.checkStringLiteralArgumentAttr(AL, 1, Replacement))
return;
- if (!S.getLangOpts().CPlusPlus14)
- if (AL.isCXX11Attribute() &&
- !(AL.hasScope() && AL.getScopeName()->isStr("gnu")))
- S.Diag(AL.getLoc(), diag::ext_cxx14_attr) << AL;
+ if (!S.getLangOpts().CPlusPlus14 && AL.isCXX11Attribute() && !AL.isGNUScope())
+ S.Diag(AL.getLoc(), diag::ext_cxx14_attr) << AL;
D->addAttr(::new (S.Context)
DeprecatedAttr(AL.getRange(), S.Context, Str, Replacement,
Index: lib/Sema/ParsedAttr.cpp
===================================================================
--- lib/Sema/ParsedAttr.cpp
+++ lib/Sema/ParsedAttr.cpp
@@ -103,14 +103,25 @@
#include "clang/Sema/AttrParsedAttrKinds.inc"
-static StringRef normalizeAttrName(StringRef AttrName, StringRef ScopeName,
+static StringRef normalizeAttrScopeName(StringRef ScopeName,
+ ParsedAttr::Syntax SyntaxUsed) {
+ // We currently only normalize the "__gnu__" scope name to be "gnu".
+ if ((SyntaxUsed == ParsedAttr::AS_CXX11 ||
+ SyntaxUsed == ParsedAttr::AS_C2x) &&
+ ScopeName == "__gnu__")
+ ScopeName = ScopeName.slice(2, ScopeName.size() - 2);
+ return ScopeName;
+}
+
+static StringRef normalizeAttrName(StringRef AttrName,
+ StringRef NormalizedScopeName,
ParsedAttr::Syntax SyntaxUsed) {
// Normalize the attribute name, __foo__ becomes foo. This is only allowable
- // for GNU attributes.
+ // for GNU attributes, and attributes using the double square bracket syntax.
bool IsGNU = SyntaxUsed == ParsedAttr::AS_GNU ||
((SyntaxUsed == ParsedAttr::AS_CXX11 ||
SyntaxUsed == ParsedAttr::AS_C2x) &&
- ScopeName == "gnu");
+ NormalizedScopeName == "gnu");
if (IsGNU && AttrName.size() >= 4 && AttrName.startswith("__") &&
AttrName.endswith("__"))
AttrName = AttrName.slice(2, AttrName.size() - 2);
@@ -125,7 +136,7 @@
SmallString<64> FullName;
if (ScopeName)
- FullName += ScopeName->getName();
+ FullName += normalizeAttrScopeName(ScopeName->getName(), SyntaxUsed);
AttrName = normalizeAttrName(AttrName, FullName, SyntaxUsed);
@@ -141,9 +152,10 @@
unsigned ParsedAttr::getAttributeSpellingListIndex() const {
// Both variables will be used in tablegen generated
// attribute spell list index matching code.
- StringRef Scope = ScopeName ? ScopeName->getName() : "";
- StringRef Name = normalizeAttrName(AttrName->getName(), Scope,
- (ParsedAttr::Syntax)SyntaxUsed);
+ auto Syntax = static_cast<ParsedAttr::Syntax>(SyntaxUsed);
+ StringRef Scope =
+ ScopeName ? normalizeAttrScopeName(ScopeName->getName(), Syntax) : "";
+ StringRef Name = normalizeAttrName(AttrName->getName(), Scope, Syntax);
#include "clang/Sema/AttrSpellingListIndex.inc"
Index: lib/Parse/ParseDeclCXX.cpp
===================================================================
--- lib/Parse/ParseDeclCXX.cpp
+++ lib/Parse/ParseDeclCXX.cpp
@@ -3868,7 +3868,8 @@
return false;
}
- if (ScopeName && ScopeName->getName() == "gnu") {
+ if (ScopeName &&
+ (ScopeName->getName() == "gnu" || ScopeName->getName() == "__gnu__")) {
// GNU-scoped attributes have some special cases to handle GNU-specific
// behaviors.
ParseGNUAttributeArgs(AttrName, AttrNameLoc, Attrs, EndLoc, ScopeName,
Index: lib/Basic/Attributes.cpp
===================================================================
--- lib/Basic/Attributes.cpp
+++ lib/Basic/Attributes.cpp
@@ -12,6 +12,11 @@
if (Name.size() >= 4 && Name.startswith("__") && Name.endswith("__"))
Name = Name.substr(2, Name.size() - 4);
+ // Normalize the scope name, but only for gnu attributes.
+ StringRef ScopeName = Scope ? Scope->getName() : "";
+ if (ScopeName == "__gnu__")
+ ScopeName = ScopeName.slice(2, ScopeName.size() - 2);
+
#include "clang/Basic/AttrHasAttributeImpl.inc"
return 0;
Index: include/clang/Sema/ParsedAttr.h
===================================================================
--- include/clang/Sema/ParsedAttr.h
+++ include/clang/Sema/ParsedAttr.h
@@ -383,6 +383,11 @@
IdentifierInfo *getScopeName() const { return ScopeName; }
SourceLocation getScopeLoc() const { return ScopeLoc; }
+ bool isGNUScope() const {
+ return ScopeName &&
+ (ScopeName->isStr("gnu") || ScopeName->isStr("__gnu__"));
+ }
+
bool hasParsedType() const { return HasParsedType; }
/// Is this the Microsoft __declspec(property) attribute?
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