[PATCH] D56992: Mark lambda-to-function-pointer conversion as noexcept
Ignat Loskutov via Phabricator via cfe-commits
cfe-commits at lists.llvm.org
Sun Jan 20 17:47:03 PST 2019
loskutov created this revision.
loskutov added reviewers: llvm-commits, aaron.ballman, doug.gregor.
Herald added a subscriber: cfe-commits.
Starting from C++17, [expr.prim.lambda.closure]p9 requires that "The [lambda to function pointer] conversion function [...] has a non-throwing exception specification".
This commit adds such a specification to the generated conversion functions.
Pre-C++17 standards don't have this requirement; however, they don't forbid the conversion functions to have this specification either.
For the sake of consistency, the specification is added unconditionally, no matter what standard revision is used.
Issue related: https://bugs.llvm.org/show_bug.cgi?id=40309
Repository:
rC Clang
https://reviews.llvm.org/D56992
Files:
clang/lib/Sema/SemaLambda.cpp
clang/test/AST/ast-dump-expr.cpp
clang/test/CXX/expr/expr.prim/expr.prim.lambda/p9.cpp
Index: clang/test/CXX/expr/expr.prim/expr.prim.lambda/p9.cpp
===================================================================
--- /dev/null
+++ clang/test/CXX/expr/expr.prim/expr.prim.lambda/p9.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++1z %s -verify
+// expected-no-diagnostics
+
+void test_noexcept() {
+ const auto lambda = [](int x) { return x + 1; };
+ static_assert(noexcept((int (*)(int))(lambda)),
+ "Lambda-to-function-pointer conversion is expected to be noexcept");
+}
Index: clang/test/AST/ast-dump-expr.cpp
===================================================================
--- clang/test/AST/ast-dump-expr.cpp
+++ clang/test/AST/ast-dump-expr.cpp
@@ -290,7 +290,7 @@
// CHECK-NEXT: Destructor
// CHECK-NEXT: CXXMethodDecl 0x{{[^ ]*}} <col:6, col:8> col:3 operator() 'auto () const' inline
// CHECK-NEXT: CompoundStmt
- // CHECK-NEXT: CXXConversionDecl 0x{{[^ ]*}} <col:3, col:8> col:3 implicit constexpr operator auto (*)() 'auto (*() const)()' inline
+ // CHECK-NEXT: CXXConversionDecl 0x{{[^ ]*}} <col:3, col:8> col:3 implicit constexpr operator auto (*)() 'auto (*() const noexcept)()' inline
// CHECK-NEXT: CXXMethodDecl 0x{{[^ ]*}} <col:3, col:8> col:3 implicit __invoke 'auto ()' static inline
// CHECK-NEXT: CompoundStmt 0x{{[^ ]*}} <col:7, col:8>
@@ -307,7 +307,7 @@
// CHECK-NEXT: CXXMethodDecl 0x{{[^ ]*}} <col:16, col:18> col:3 operator() 'auto (int, ...) const' inline
// CHECK-NEXT: ParmVarDecl 0x{{[^ ]*}} <col:6, col:10> col:10 a 'int'
// CHECK-NEXT: CompoundStmt
- // CHECK-NEXT: CXXConversionDecl 0x{{[^ ]*}} <col:3, col:18> col:3 implicit constexpr operator auto (*)(int, ...) 'auto (*() const)(int, ...)' inline
+ // CHECK-NEXT: CXXConversionDecl 0x{{[^ ]*}} <col:3, col:18> col:3 implicit constexpr operator auto (*)(int, ...) 'auto (*() const noexcept)(int, ...)' inline
// CHECK-NEXT: CXXMethodDecl 0x{{[^ ]*}} <col:3, col:18> col:3 implicit __invoke 'auto (int, ...)' static inline
// CHECK-NEXT: ParmVarDecl 0x{{[^ ]*}} <col:6, col:10> col:10 a 'int'
// CHECK-NEXT: CompoundStmt 0x{{[^ ]*}} <col:17, col:18>
@@ -455,7 +455,7 @@
// CHECK-NEXT: Destructor
// CHECK-NEXT: CXXMethodDecl 0x{{[^ ]*}} <col:8, col:19> col:3 constexpr operator() 'auto () const' inline
// CHECK-NEXT: CompoundStmt
- // CHECK-NEXT: CXXConversionDecl 0x{{[^ ]*}} <col:3, col:19> col:3 implicit constexpr operator auto (*)() 'auto (*() const)()' inline
+ // CHECK-NEXT: CXXConversionDecl 0x{{[^ ]*}} <col:3, col:19> col:3 implicit constexpr operator auto (*)() 'auto (*() const noexcept)()' inline
// CHECK-NEXT: CXXMethodDecl 0x{{[^ ]*}} <col:3, col:19> col:3 implicit __invoke 'auto ()' static inline
// CHECK-NEXT: CompoundStmt 0x{{[^ ]*}} <col:18, col:19>
@@ -471,7 +471,7 @@
// CHECK-NEXT: Destructor
// CHECK-NEXT: CXXMethodDecl 0x{{[^ ]*}} <col:8, col:17> col:3 operator() 'auto ()' inline
// CHECK-NEXT: CompoundStmt
- // CHECK-NEXT: CXXConversionDecl 0x{{[^ ]*}} <col:3, col:17> col:3 implicit constexpr operator auto (*)() 'auto (*() const)()' inline
+ // CHECK-NEXT: CXXConversionDecl 0x{{[^ ]*}} <col:3, col:17> col:3 implicit constexpr operator auto (*)() 'auto (*() const noexcept)()' inline
// CHECK-NEXT: CXXMethodDecl 0x{{[^ ]*}} <col:3, col:17> col:3 implicit __invoke 'auto ()' static inline
// CHECK-NEXT: CompoundStmt 0x{{[^ ]*}} <col:16, col:17>
@@ -487,7 +487,7 @@
// CHECK-NEXT: Destructor
// CHECK-NEXT: CXXMethodDecl 0x{{[^ ]*}} <col:8, col:18> col:3 operator() 'auto () const noexcept' inline
// CHECK-NEXT: CompoundStmt
- // CHECK-NEXT: CXXConversionDecl 0x{{[^ ]*}} <col:3, col:18> col:3 implicit constexpr operator auto (*)() noexcept 'auto (*() const)() noexcept' inline
+ // CHECK-NEXT: CXXConversionDecl 0x{{[^ ]*}} <col:3, col:18> col:3 implicit constexpr operator auto (*)() noexcept 'auto (*() const noexcept)() noexcept' inline
// CHECK-NEXT: CXXMethodDecl 0x{{[^ ]*}} <col:3, col:18> col:3 implicit __invoke 'auto () noexcept' static inline
// CHECK-NEXT: CompoundStmt 0x{{[^ ]*}} <col:17, col:18>
@@ -505,7 +505,7 @@
// CHECK-NEXT: CompoundStmt
// CHECK-NEXT: ReturnStmt 0x{{[^ ]*}} <col:17, col:24>
// CHECK-NEXT: IntegerLiteral 0x{{[^ ]*}} <col:24> 'int' 0
- // CHECK-NEXT: CXXConversionDecl 0x{{[^ ]*}} <col:3, col:27> col:3 implicit constexpr operator int (*)() 'auto (*() const)() -> int' inline
+ // CHECK-NEXT: CXXConversionDecl 0x{{[^ ]*}} <col:3, col:27> col:3 implicit constexpr operator int (*)() 'auto (*() const noexcept)() -> int' inline
// CHECK-NEXT: CXXMethodDecl 0x{{[^ ]*}} <col:3, col:27> col:3 implicit __invoke 'auto () -> int' static inline
// CHECK-NEXT: CompoundStmt 0x{{[^ ]*}} <col:15, col:27>
// CHECK-NEXT: ReturnStmt 0x{{[^ ]*}} <col:17, col:24>
@@ -568,4 +568,4 @@
// CHECK: CallExpr 0x{{[^ ]*}} <line:[[@LINE+1]]:{{[^>]+}}> 'void'{{$}}
f(x);
}
-} // namespace test_adl_call_three
\ No newline at end of file
+} // namespace test_adl_call_three
Index: clang/lib/Sema/SemaLambda.cpp
===================================================================
--- clang/lib/Sema/SemaLambda.cpp
+++ clang/lib/Sema/SemaLambda.cpp
@@ -1228,8 +1228,11 @@
S.Context.getDefaultCallingConvention(
/*IsVariadic=*/false, /*IsCXXMethod=*/true));
// The conversion function is always const.
+ // C++17 also obliges it to be noexcept (which it in fact is),
+ // and previous standards don't forbid that either.
ConvExtInfo.TypeQuals = Qualifiers();
ConvExtInfo.TypeQuals.addConst();
+ ConvExtInfo.ExceptionSpec.Type = EST_BasicNoexcept;
QualType ConvTy =
S.Context.getFunctionType(PtrToFunctionTy, None, ConvExtInfo);
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