aaron.ballman created this revision.
aaron.ballman added reviewers: erichkeane, jyknight, rsmith.
aaron.ballman requested review of this revision.
Herald added a project: clang.
This adds support for
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2764.pdf, which was adopted at
the Feb 2022 WG14 meeting. That paper adds `[[noreturn]]` and `[[_Noreturn]]`
to the list of supported attributes in C2x. These attributes have the same
semantics as the `[[noreturn]]` attribute in C++.
The `[[_Noreturn]]` attribute was added as a deprecated feature so that
translation units which include `<stdnoreturn.h>` do not get an error on use of
`[[noreturn]]` because the macro expands to `_Noreturn`. Users can use
`-Wno-deprecated-attributes` to silence the diagnostic.
Use of `<stdnotreturn.h>` or the `noreturn` macro were both deprecated. Users
can define the `_CLANG_DISABLE_CRT_DEPRECATION_WARNINGS` macro to suppress the
deprecation diagnostics coming from the header file.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D119707
Files:
clang/docs/ReleaseNotes.rst
clang/include/clang/Basic/Attr.td
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/Headers/stdnoreturn.h
clang/lib/Sema/SemaDeclAttr.cpp
clang/test/AST/ast-dump-lambda.cpp
clang/test/Sema/c2x-noreturn.c
Index: clang/test/Sema/c2x-noreturn.c
===================================================================
--- /dev/null
+++ clang/test/Sema/c2x-noreturn.c
@@ -0,0 +1,64 @@
+// RUN: %clang_cc1 -verify=all,c2x -std=c2x -fsyntax-only %s
+// RUN: %clang_cc1 -verify=all -std=c17 -fdouble-square-bracket-attributes -fsyntax-only %s
+// RUN: %clang_cc1 -verify=none -Wno-deprecated-attributes -D_CLANG_DISABLE_CRT_DEPRECATION_WARNINGS -std=c2x -fsyntax-only %s
+// RUN: %clang_cc1 -verify=none -Wno-deprecated-attributes -D_CLANG_DISABLE_CRT_DEPRECATION_WARNINGS -std=c17 -fdouble-square-bracket-attributes -fsyntax-only %s
+// none-no-diagnostics
+
+// Test preprocessor functionality.
+#if !__has_c_attribute(noreturn)
+#error "No noreturn attribute support?"
+#endif
+
+#if !__has_c_attribute(_Noreturn)
+#error "No _Noreturn attribute support?"
+#endif
+
+#if __has_c_attribute(noreturn) != __has_c_attribute(_Noreturn) || \
+ __has_c_attribute(noreturn) != 202202L
+#error "Wrong value for __has_c_attribute(noreturn)"
+#endif
+
+// If we're testings with deprecations disabled, we don't care about testing
+// the scenarios that trigger errors because we're only interested in the
+// deprecation warning behaviors.
+#ifndef _CLANG_DISABLE_CRT_DEPRECATION_WARNINGS
+// Test that the attribute accepts no args, applies to the correct subject, etc.
+[[noreturn(12)]] void func4(void); // all-error {{attribute 'noreturn' cannot have an argument list}}
+[[noreturn]] int not_a_func; // all-error {{'noreturn' attribute only applies to functions}}
+void func5(void) [[noreturn]]; // all-error {{'noreturn' attribute cannot be applied to types}}
+#endif
+
+_Noreturn void func1(void); // ok, using the function specifier
+[[noreturn]] void func2(void);
+
+// This is deprecated because it's only for compatibility with inclusion of the
+// <stdnoreturn.h> header where the noreturn macro expands to _Noreturn.
+[[_Noreturn]] void func3(void); // all-warning {{the '[[_Noreturn]]' attribute spelling is deprecated in C2x; use '[[noreturn]]' instead}}
+
+// Test the behavior of including <stdnoreturn.h>
+#include <stdnoreturn.h> // c2x-warning@stdnoreturn.h:* {{the '<stdnoreturn.h>' header is deprecated in C2x}}
+
+[[noreturn]] void func6(void); // all-warning {{the '[[_Noreturn]]' attribute spelling is deprecated in C2x; use '[[noreturn]]' instead}} \
+ // c2x-warning {{macro 'noreturn' has been marked as deprecated}} \
+ // c2x-note@stdnoreturn.h:* {{macro marked 'deprecated' here}}
+
+void func7 [[noreturn]] (void); // all-warning {{the '[[_Noreturn]]' attribute spelling is deprecated in C2x; use '[[noreturn]]' instead}} \
+ // c2x-warning {{macro 'noreturn' has been marked as deprecated}} \
+ // c2x-note@stdnoreturn.h:* {{macro marked 'deprecated' here}}
+
+noreturn void func8(void); // c2x-warning {{macro 'noreturn' has been marked as deprecated}} \
+ // c2x-note@stdnoreturn.h:* {{macro marked 'deprecated' here}}
+
+// Ensure the function specifier form still works
+void noreturn func9(void); // c2x-warning {{macro 'noreturn' has been marked as deprecated}} \
+ // c2x-note@stdnoreturn.h:* {{macro marked 'deprecated' here}}
+
+// Test preprocessor functionality after including <stdnoreturn.h>.
+#if !__has_c_attribute(noreturn) // c2x-warning {{macro 'noreturn' has been marked as deprecated}} \
+ // c2x-note@stdnoreturn.h:* {{macro marked 'deprecated' here}}
+#error "No noreturn attribute support?"
+#endif
+
+#if !__has_c_attribute(_Noreturn)
+#error "No _Noreturn attribute support?"
+#endif
Index: clang/test/AST/ast-dump-lambda.cpp
===================================================================
--- clang/test/AST/ast-dump-lambda.cpp
+++ clang/test/AST/ast-dump-lambda.cpp
@@ -305,7 +305,7 @@
// CHECK-NEXT: | | `-Destructor simple irrelevant trivial needs_implicit
// CHECK-NEXT: | |-CXXMethodDecl {{.*}} <col:20, col:23> col:3{{( imported)?}} operator() 'auto () const' inline
// CHECK-NEXT: | | |-CompoundStmt {{.*}} <col:22, col:23>
-// CHECK-NEXT: | | `-CXX11NoReturnAttr {{.*}} <col:8>
+// CHECK-NEXT: | | `-CXX11NoReturnAttr {{.*}} <col:8> noreturn
// CHECK-NEXT: | |-CXXConversionDecl {{.*}} <col:3, col:23> col:3{{( imported)?}} implicit constexpr operator auto (*)() 'auto (*() const noexcept)()' inline
// CHECK-NEXT: | `-CXXMethodDecl {{.*}} <col:3, col:23> col:3{{( imported)?}} implicit __invoke 'auto ()' static inline
// CHECK-NEXT: `-CompoundStmt {{.*}} <col:22, col:23>
Index: clang/lib/Sema/SemaDeclAttr.cpp
===================================================================
--- clang/lib/Sema/SemaDeclAttr.cpp
+++ clang/lib/Sema/SemaDeclAttr.cpp
@@ -2175,6 +2175,16 @@
D->addAttr(::new (S.Context) NoReturnAttr(S.Context, Attrs));
}
+static void handleStandardNoReturnAttr(Sema &S, Decl *D, const ParsedAttr &A) {
+ // The [[_Noreturn]] spelling is deprecated in C2x, so if that was used,
+ // issue an appropriate diagnostic.
+ if (!S.getLangOpts().CPlusPlus &&
+ A.getSemanticSpelling() == CXX11NoReturnAttr::C2x_Noreturn)
+ S.Diag(A.getLoc(), diag::warn_deprecated_noreturn_spelling) << A.getRange();
+
+ D->addAttr(::new (S.Context) CXX11NoReturnAttr(S.Context, A));
+}
+
static void handleNoCfCheckAttr(Sema &S, Decl *D, const ParsedAttr &Attrs) {
if (!S.getLangOpts().CFProtectionBranch)
S.Diag(Attrs.getLoc(), diag::warn_nocf_check_attribute_ignored);
@@ -8432,6 +8442,9 @@
case ParsedAttr::AT_NoReturn:
handleNoReturnAttr(S, D, AL);
break;
+ case ParsedAttr::AT_CXX11NoReturn:
+ handleStandardNoReturnAttr(S, D, AL);
+ break;
case ParsedAttr::AT_AnyX86NoCfCheck:
handleNoCfCheckAttr(S, D, AL);
break;
Index: clang/lib/Headers/stdnoreturn.h
===================================================================
--- clang/lib/Headers/stdnoreturn.h
+++ clang/lib/Headers/stdnoreturn.h
@@ -13,4 +13,13 @@
#define noreturn _Noreturn
#define __noreturn_is_defined 1
+#if __STDC_VERSION__ > 201710L && \
+ !defined(_CLANG_DISABLE_CRT_DEPRECATION_WARNINGS)
+/* The noreturn macro is deprecated in C2x. */
+#pragma clang deprecated(noreturn)
+
+/* Including the header file in C2x is also deprecated. */
+#warning "the '<stdnoreturn.h>' header is deprecated in C2x"
+#endif
+
#endif /* __STDNORETURN_H */
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -4027,6 +4027,9 @@
"specifying vector types with the 'mode' attribute is deprecated; "
"use the 'vector_size' attribute instead">,
InGroup<DeprecatedAttributes>;
+def warn_deprecated_noreturn_spelling : Warning<
+ "the '[[_Noreturn]]' attribute spelling is deprecated in C2x; use "
+ "'[[noreturn]]' instead">, InGroup<DeprecatedAttributes>;
def err_complex_mode_vector_type : Error<
"type of machine mode does not support base vector types">;
def err_enum_mode_vector_type : Error<
Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -1209,10 +1209,10 @@
}
def CXX11NoReturn : InheritableAttr {
- let Spellings = [CXX11<"", "noreturn", 200809>];
+ let Spellings = [CXX11<"", "noreturn", 200809>,
+ C2x<"", "noreturn", 202202>, C2x<"", "_Noreturn", 202202>];
let Subjects = SubjectList<[Function], ErrorDiag>;
let Documentation = [CXX11NoReturnDocs];
- let SimpleHandler = 1;
}
// Similar to CUDA, OpenCL attributes do not receive a [[]] spelling because
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -89,6 +89,11 @@
C Language Changes in Clang
---------------------------
+C2x Feature Support
+-------------------
+
+- Implemented `WG14 N2674 The noreturn attribute <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2764.pdf>`_.
+
C++ Language Changes in Clang
-----------------------------
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