Closed
Description
namespace ns
{
consteval int foo(int x) { return 1; }
}
template <class A>
struct T {
static constexpr auto xx = ns::foo(A{});
};crash with
Stack dump:
0. Program arguments: /opt/compiler-explorer/clang-trunk/bin/clang++ -gdwarf-4 -g -o /app/output.s -mllvm --x86-asm-syntax=intel -S --gcc-toolchain=/opt/compiler-explorer/gcc-snapshot -fcolor-diagnostics -fno-crash-diagnostics -std=c++20 <source> -isystem/opt/compiler-explorer/libs/catch2/v3.0.1/src
1. <source>:9:44: current parser token ';'
2. <source>:8:1: parsing struct/union/class body 'T'
#0 0x00000000033cba18 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x33cba18)
#1 0x00000000033c9b44 llvm::sys::CleanupOnSignal(unsigned long) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x33c9b44)
#2 0x0000000003318b68 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
#3 0x00007fc4f42c7420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
#4 0x0000000000ad8e28 clang::Sema::MarkExpressionAsImmediateEscalating(clang::Expr*) (.cold) SemaExpr.cpp:0:0
#5 0x0000000005f39f3d clang::Sema::PopExpressionEvaluationContext() (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5f39f3d)
#6 0x0000000005a025e4 clang::Parser::ParseCXXMemberInitializer(clang::Decl*, bool, clang::SourceLocation&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5a025e4)
#7 0x0000000005a15a5f clang::Parser::ParseCXXClassMemberDeclaration(clang::AccessSpecifier, clang::ParsedAttributes&, clang::Parser::ParsedTemplateInfo const&, clang::ParsingDeclRAIIObject*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5a15a5f)
#8 0x0000000005a16d34 clang::Parser::ParseCXXClassMemberDeclarationWithPragmas(clang::AccessSpecifier&, clang::ParsedAttributes&, clang::TypeSpecifierType, clang::Decl*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5a16d34)
#9 0x0000000005a173a6 clang::Parser::ParseCXXMemberSpecification(clang::SourceLocation, clang::SourceLocation, clang::ParsedAttributes&, unsigned int, clang::Decl*) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5a173a6)
#10 0x0000000005a19679 clang::Parser::ParseClassSpecifier(clang::tok::TokenKind, clang::SourceLocation, clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, bool, clang::Parser::DeclSpecContext, clang::ParsedAttributes&) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x5a19679)
#11 0x00000000059e9414 clang::Parser::ParseDeclarationSpecifiers(clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, clang::Parser::DeclSpecContext, clang::Parser::LateParsedAttrList*, clang::ImplicitTypenameContext) (/opt/compiler-explorer/clang-trunk/bin/clang+++0x59e9414)
....
https://godbolt.org/z/5a8hPo5je
On Clang 16, this used to error out with :
<source>:9:32: error: cannot take address of consteval function 'foo' outside of an immediate invocation
static constexpr auto xx = ns::foo(A{});
^
<source>:4:19: note: declared here
consteval int foo(int x) { return 1; }
I think the problem stems from
1/ during the parsing of the initializer, the ExpressionEvaluationContext is not set to ConstantEvaluated, so the reference to ns::foo is added to ReferenceToConsteval
2/ When popping the Sema::PopExpressionEvalContext is called, Context.InImmediateEscalatingFunctionContext is true, most likely because ParseCXXMemberInitializer contains this line :
Actions.ExprEvalContexts.back().InImmediateEscalatingFunctionContext = true;
Which does not makes a lot of sense to me (besides this kind of state mutation would be more suitable on the Sema side? e.g. in Sema::ActOnStartCXXInClassMemberInitializer/Finish).
Finally, the evaluation context should probably be set to ConstantEvaluated when the variable is constexpr to not error on the declaration reference.