Assertion failure with invalid code, fatal errors, and unused warning as error "Unaccounted cleanups in function"

[davidstone]

Bugzilla Link	49630
Version	trunk
OS	Linux
CC	@DougGregor,@zygoloid

Extended Description

The following code

template<typename T>
void a(T &&s) {
}

void b() {
	int sum = a(0);
}

when compiled with clang++ -Werror=unused-parameter -Wfatal-errors -o /dev/null -c ~/test/crash.cpp

causes clang to crash with

/home/david/test/crash.cpp:2:12: fatal error: unused parameter 's' [-Wunused-parameter]
void a(T &&s) {
           ^
clang++: /home/david/llvm/clang/lib/Sema/SemaDecl.cpp:14661: clang::Decl* clang::Sema::ActOnFinishFunctionBody(clang::Decl*, clang::Stmt*, bool): Assertion `!Cleanup.exprNeedsCleanups() && "Unaccounted cleanups in function"' failed.
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: clang++ -Werror=unused-parameter -Wfatal-errors -o /dev/null -c /home/david/test/crash.cpp
1.      <eof> parser at end of file
2.      /home/david/test/crash.cpp:5:10: parsing function body 'b'
 #&#8203;0 0x0000564da2880f6d llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/david/llvm/build/bin/clang-13+0x1f46f6d)
 #&#8203;1 0x0000564da287eb84 llvm::sys::RunSignalHandlers() (/home/david/llvm/build/bin/clang-13+0x1f44b84)
 #&#8203;2 0x0000564da27e0228 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
 #&#8203;3 0x00007fc991af6960 __restore_rt sigaction.c:0:0
 #&#8203;4 0x00007fc99153bef5 raise (/usr/lib/libc.so.6+0x3cef5)
 #&#8203;5 0x00007fc991525862 abort (/usr/lib/libc.so.6+0x26862)
 #&#8203;6 0x00007fc991525747 _nl_load_domain.cold loadmsgcat.c:0:0
 #&#8203;7 0x00007fc991534646 (/usr/lib/libc.so.6+0x35646)
 #&#8203;8 0x0000564da4b68e92 clang::Sema::ActOnFinishFunctionBody(clang::Decl*, clang::Stmt*, bool) (/home/david/llvm/build/bin/clang-13+0x422ee92)
 #&#8203;9 0x0000564da498b717 clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) (/home/david/llvm/build/bin/clang-13+0x4051717)
#&#8203;10 0x0000564da48cda02 clang::Parser::ParseFunctionDefinition(clang::ParsingDeclarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::LateParsedAttrList*) (/home/david/llvm/build/bin/clang-13+0x3f93a02)
#&#8203;11 0x0000564da48fa1ab clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::SourceLocation*, clang::Parser::ForRangeInit*) (/home/david/llvm/build/bin/clang-13+0x3fc01ab)
#&#8203;12 0x0000564da48ca582 clang::Parser::ParseDeclarationOrFunctionDefinition(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*, clang::AccessSpecifier) (.part.0) Parser.cpp:0:0
#&#8203;13 0x0000564da48d0ad6 clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*) (/home/david/llvm/build/bin/clang-13+0x3f96ad6)
#&#8203;14 0x0000564da48d17b8 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, bool) (/home/david/llvm/build/bin/clang-13+0x3f977b8)
#&#8203;15 0x0000564da48c3e09 clang::ParseAST(clang::Sema&, bool, bool) (/home/david/llvm/build/bin/clang-13+0x3f89e09)
#&#8203;16 0x0000564da320f6a9 clang::FrontendAction::Execute() (/home/david/llvm/build/bin/clang-13+0x28d56a9)
#&#8203;17 0x0000564da31a0095 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/home/david/llvm/build/bin/clang-13+0x2866095)
#&#8203;18 0x0000564da32d2663 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/home/david/llvm/build/bin/clang-13+0x2998663)
#&#8203;19 0x0000564da14fb641 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (/home/david/llvm/build/bin/clang-13+0xbc1641)
#&#8203;20 0x0000564da14f6df0 ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&) driver.cpp:0:0
#&#8203;21 0x0000564da3034185 void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<llvm::Optional<llvm::StringRef> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, bool*) const::'lambda'()>(long) Job.cpp:0:0
#&#8203;22 0x0000564da27e03b4 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (/home/david/llvm/build/bin/clang-13+0x1ea63b4)
#&#8203;23 0x0000564da303539b clang::driver::CC1Command::Execute(llvm::ArrayRef<llvm::Optional<llvm::StringRef> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, bool*) const (.part.0) Job.cpp:0:0
#&#8203;24 0x0000564da3007ee8 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&) const (/home/david/llvm/build/bin/clang-13+0x26cdee8)
#&#8203;25 0x0000564da3008a19 clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*> >&) const (/home/david/llvm/build/bin/clang-13+0x26cea19)
#&#8203;26 0x0000564da3014ce1 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*> >&) (/home/david/llvm/build/bin/clang-13+0x26dace1)
#&#8203;27 0x0000564da1463748 main (/home/david/llvm/build/bin/clang-13+0xb29748)
#&#8203;28 0x00007fc991526b25 __libc_start_main (/usr/lib/libc.so.6+0x27b25)
#&#8203;29 0x0000564da14f676e _start (/home/david/llvm/build/bin/clang-13+0xbbc76e)
clang-13: fatal error: clang frontend command failed with exit code 134 (use -v to see invocation)
clang version 13.0.0 (https://github.com/llvm/llvm-project.git 420d90d8137e9de7cda7c948f43ea4e50703d75f)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/david/llvm/build/bin
clang-13: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang-13: note: diagnostic msg: /tmp/crash-968831.cpp
clang-13: note: diagnostic msg: /tmp/crash-968831.sh
clang-13: note: diagnostic msg: 

********************

[davidstone]

Still an issue on trunk

https://godbolt.org/z/oG49Wj4zz

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[shafik]

Reduced a bit: https://godbolt.org/z/1sT6nej3d

void a(int &&s) {} // Looks like we need && here and we need a body

void b() {
	int sum = a(0); // Looks like we need to assign it to a variable
}

[shafik]

It looks like in other places where we assert !Cleanup.exprNeedsCleanups() we also do

if (hasAnyUnrecoverableErrorsInThisFunction())
    DiscardCleanupsInEvaluationContext();

In this case in Sema::ActOnFinishFunctionBody(...) we only check hasUncompilableErrorOccurred() which missed that a fatal error has occurred.

I think we need to modify it to also check hasAnyUnrecoverableErrorsInThisFunction()

[Fznamznon]

https://reviews.llvm.org/D158827