https://github.com/MitalAshok created
https://github.com/llvm/llvm-project/pull/102044
Added a new `-Wpre-c++26-compat` warning for when this feature is used in
C++26, and a different warning for when this is used in C++11 through C++20.
>From 65f4c93a54888338ab5fe3e5b9f9f1228651eb3c Mon Sep 17 00:00:00 2001
From: Mital Ashok <mi...@mitalashok.co.uk>
Date: Mon, 5 Aug 2024 20:29:12 +0100
Subject: [PATCH] [Clang][Sema] Backport P2741R3 (static_assert with
user-generated message) to C++11
---
clang/docs/LanguageExtensions.rst | 2 ++
.../clang/Basic/DiagnosticParseKinds.td | 6 ++++
clang/lib/Frontend/InitPreprocessor.cpp | 6 ++--
clang/lib/Parse/ParseDeclCXX.cpp | 10 +++++--
clang/test/Lexer/cxx-features.cpp | 2 +-
clang/test/SemaCXX/static-assert-ext.cpp | 28 +++++++++++++++++++
6 files changed, 46 insertions(+), 8 deletions(-)
create mode 100644 clang/test/SemaCXX/static-assert-ext.cpp
diff --git a/clang/docs/LanguageExtensions.rst
b/clang/docs/LanguageExtensions.rst
index be07f81cc41b0..5953ca5259da2 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -1483,6 +1483,7 @@ Generic lambda expressions
__cpp_generic_lambdas C+
variable templates __cpp_variable_templates
C++14 C++03
Binary literals __cpp_binary_literals
C++14 C++03
Relaxed constexpr __cpp_constexpr
C++14 C++11
+Static assert with no message __cpp_static_assert>=201411L
C++17 C++11
Pack expansion in generalized lambda-capture __cpp_init_captures
C++17 C++03
``if constexpr`` __cpp_if_constexpr
C++17 C++11
fold expressions __cpp_fold_expressions
C++17 C++03
@@ -1503,6 +1504,7 @@ Conditional ``explicit``
__cpp_conditional_explicit C+
``static operator()`` __cpp_static_call_operator
C++23 C++03
Attributes on Lambda-Expressions
C++23 C++11
Attributes on Structured Bindings __cpp_structured_bindings
C++26 C++03
+Static assert with user-generated message __cpp_static_assert>=202306L
C++26 C++11
Pack Indexing __cpp_pack_indexing
C++26 C++03
``= delete ("should have a reason");`` __cpp_deleted_function
C++26 C++03
-------------------------------------------- --------------------------------
------------- -------------
diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td
b/clang/include/clang/Basic/DiagnosticParseKinds.td
index f8d50d12bb935..eaad99451eb7f 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -470,6 +470,12 @@ def warn_c17_compat_static_assert_no_message : Warning<
"'_Static_assert' with no message is incompatible with C standards before "
"C23">,
DefaultIgnore, InGroup<CPre23Compat>;
+def ext_cxx_static_assert_user_generated_message : ExtWarn<
+ "'static_assert' with a user-generated message is a C++26 extension">,
+ InGroup<CXX26>;
+def warn_cxx20_compat_static_assert_user_generated_message : Warning<
+ "'static_assert' with a user-generated message is incompatible with "
+ "C++ standards before C++26">, DefaultIgnore, InGroup<CXXPre26Compat>;
def err_function_definition_not_allowed : Error<
"function definition is not allowed here">;
def err_expected_end_of_enumerator : Error<
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp
b/clang/lib/Frontend/InitPreprocessor.cpp
index 8e62461d8a181..038fad5272be7 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -671,10 +671,8 @@ static void InitializeCPlusPlusFeatureTestMacros(const
LangOptions &LangOpts,
LangOpts.CPlusPlus23 ? "202211L"
: LangOpts.CPlusPlus17 ? "201603L"
: "200907");
- Builder.defineMacro("__cpp_static_assert", LangOpts.CPlusPlus26 ? "202306L"
- : LangOpts.CPlusPlus17
- ? "201411L"
- : "200410");
+ // C++17 / C++26 static_assert backported
+ Builder.defineMacro("__cpp_static_assert", "202306L");
Builder.defineMacro("__cpp_decltype", "200707L");
Builder.defineMacro("__cpp_attributes", "200809L");
Builder.defineMacro("__cpp_rvalue_references", "200610L");
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index aac89d910bbc8..87ba660c35b55 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -1073,7 +1073,7 @@ Decl *Parser::ParseStaticAssertDeclaration(SourceLocation
&DeclEnd) {
}
bool ParseAsExpression = false;
- if (getLangOpts().CPlusPlus26) {
+ if (getLangOpts().CPlusPlus11) {
for (unsigned I = 0;; ++I) {
const Token &T = GetLookAheadToken(I);
if (T.is(tok::r_paren))
@@ -1085,9 +1085,13 @@ Decl
*Parser::ParseStaticAssertDeclaration(SourceLocation &DeclEnd) {
}
}
- if (ParseAsExpression)
+ if (ParseAsExpression) {
+ Diag(Tok,
+ getLangOpts().CPlusPlus26
+ ? diag::warn_cxx20_compat_static_assert_user_generated_message
+ : diag::ext_cxx_static_assert_user_generated_message);
AssertMessage = ParseConstantExpressionInExprEvalContext();
- else if (tokenIsLikeStringLiteral(Tok, getLangOpts()))
+ } else if (tokenIsLikeStringLiteral(Tok, getLangOpts()))
AssertMessage = ParseUnevaluatedStringLiteralExpression();
else {
Diag(Tok, diag::err_expected_string_literal)
diff --git a/clang/test/Lexer/cxx-features.cpp
b/clang/test/Lexer/cxx-features.cpp
index 08b732132228b..47e9ae9f5d2c5 100644
--- a/clang/test/Lexer/cxx-features.cpp
+++ b/clang/test/Lexer/cxx-features.cpp
@@ -321,7 +321,7 @@
#error "wrong value for __cpp_range_based_for"
#endif
-#if check(static_assert, 0, 200410, 200410, 201411, 201411, 201411, 202306)
+#if check(static_assert, 0, 202306, 202306, 202306, 202306, 202306, 202306)
#error "wrong value for __cpp_static_assert"
#endif
diff --git a/clang/test/SemaCXX/static-assert-ext.cpp
b/clang/test/SemaCXX/static-assert-ext.cpp
new file mode 100644
index 0000000000000..05f7a0e96974a
--- /dev/null
+++ b/clang/test/SemaCXX/static-assert-ext.cpp
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -std=c++98 -fsyntax-only -pedantic %s
-verify=precxx11,precxx17,precxx26
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -pedantic %s
-verify=since-cxx11,precxx17,precxx26 -Wc++98-compat
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only -pedantic %s
-verify=since-cxx11,since-cxx17,precxx26 -Wc++98-compat -Wpre-c++17-compat
+// RUN: %clang_cc1 -std=c++26 -fsyntax-only -pedantic %s
-verify=since-cxx11,since-cxx17,since-cxx26 -Wc++98-compat -Wpre-c++17-compat
-Wpre-c++26-compat
+
+static_assert(false, "a");
+// precxx11-error@-1 {{a type specifier is required for all declarations}}
+// since-cxx11-warning@-2 {{'static_assert' declarations are incompatible with
C++98}}
+// since-cxx11-error@-3 {{static assertion failed: a}}
+
+#if __cplusplus >= 201103L
+static_assert(false);
+// since-cxx11-warning@-1 {{'static_assert' declarations are incompatible with
C++98}}
+// precxx17-warning@-2 {{'static_assert' with no message is a C++17 extension}}
+// since-cxx17-warning@-3 {{'static_assert' with no message is incompatible
with C++ standards before C++17}}
+// since-cxx11-error@-4 {{static assertion failed}}
+
+struct X {
+ static constexpr int size() { return 1; } // since-cxx11-warning
{{'constexpr'}}
+ static constexpr const char* data() { return "b"; } // since-cxx11-warning
{{'constexpr'}}
+};
+
+static_assert(false, X());
+// since-cxx11-warning@-1 {{'static_assert' declarations are incompatible with
C++98}}
+// precxx26-warning@-2 {{'static_assert' with a user-generated message is a
C++26 extension}}
+// since-cxx26-warning@-3 {{'static_assert' with a user-generated message is
incompatible with C++ standards before C++26}}
+// since-cxx11-error@-4 {{static assertion failed: b}}
+#endif
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