"Declaration may not be in a Comdat" when using D3DX12 headers and PCH files

[llvmbot]

Bugzilla Link	44953
Resolution	FIXED
Resolved on	Feb 27, 2020 05:44
Version	trunk
OS	Windows NT
Blocks	#43900
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor,@zmodem,@llunak,@zygoloid,@rnk

Extended Description

When including D3DX12 [1] headers in .PCH headers (/Yc), and using them in TUs (/Yu), clang-cl fails with the following error:

Declaration may not be in a Comdat!
%struct.CD3DX12_DEFAULT* @"?D3D12_DEFAULT@@3UCD3DX12_DEFAULT@@B"
fatal error: error in backend: Broken module found, compilation aborted!
Stack dump:
0.      Program arguments: F:\llvm-project\build\bin\clang-cl.exe /Yuprecomp.h a.cpp /c
1.      <eof> parser at end of file
2.      Per-function optimization
 #&#8203;0 0x00007ffa8b5ba839 (C:\WINDOWS\System32\KERNELBASE.dll+0x3a839)
 #&#8203;1 0x00007ff7690e5dda llvm::CrashRecoveryContext::HandleExit(int) F:\llvm-project\llvm\lib\Support\CrashRecoveryContext.cpp:436:0
 #&#8203;2 0x00007ff769129484 llvm::sys::Process::Exit(int) F:\llvm-project\llvm\lib\Support\Process.cpp:95:0
 #&#8203;3 0x00007ff7688982c9 LLVMErrorHandler F:\llvm-project\clang\tools\driver\cc1_main.cpp:73:0
 #&#8203;4 0x00007ff7690e60ea llvm::report_fatal_error(class llvm::Twine const &, bool) F:\llvm-project\llvm\lib\Support\ErrorHandling.cpp:108:0
 #&#8203;5 0x00007ff7690e6001 llvm::report_fatal_error(char const *, bool) F:\llvm-project\llvm\lib\Support\ErrorHandling.cpp:83:0
 #&#8203;6 0x00007ff769f2ff38 `anonymous namespace'::VerifierLegacyPass::doFinalization F:\llvm-project\llvm\lib\IR\Verifier.cpp:5189:0
 #&#8203;7 0x00007ff768cda3af llvm::FPPassManager::doFinalization(class llvm::Module &) F:\llvm-project\llvm\lib\IR\LegacyPassManager.cpp:1536:0
 #&#8203;8 0x00007ff768cd96e0 llvm::legacy::FunctionPassManagerImpl::doFinalization(class llvm::Module &) F:\llvm-project\llvm\lib\IR\LegacyPassManager.cpp:1382:0
 #&#8203;9 0x00007ff76a3d11e1 clang::EmitBackendOutput(class clang::DiagnosticsEngine &, class clang::HeaderSearchOptions const &, class clang::CodeGenOptions const &, class clang::TargetOptions const &, class clang::LangOptions const &, class llvm::DataLayout const &, class llvm::Module *, enum clang::BackendAction, class std::unique_ptr<class llvm::raw_pwrite_stream, struct std::default_delete<class llvm::raw_pwrite_stream>>) F:\llvm-project\clang\lib\CodeGen\BackendUtil.cpp:1582:0
llvm/llvm-project#382 0x00007ff76a75a4c6 clang::BackendConsumer::HandleTranslationUnit(class clang::ASTContext &) F:\llvm-project\clang\lib\CodeGen\CodeGenAction.cpp:339:0
llvm/llvm-project#383 0x00007ff76c175c43 clang::ParseAST(class clang::Sema &, bool, bool) F:\llvm-project\clang\lib\Parse\ParseAST.cpp:178:0
llvm/llvm-project#384 0x00007ff76a6b2edd clang::FrontendAction::Execute(void) F:\llvm-project\clang\lib\Frontend\FrontendAction.cpp:944:0
llvm/llvm-project#385 0x00007ff76924e70b clang::CompilerInstance::ExecuteAction(class clang::FrontendAction &) F:\llvm-project\clang\lib\Frontend\CompilerInstance.cpp:969:0
llvm/llvm-project#386 0x00007ff7692b405d clang::ExecuteCompilerInvocation(class clang::CompilerInstance *) F:\llvm-project\clang\lib\FrontendTool\ExecuteCompilerInvocation.cpp:292:0
llvm/llvm-project#387 0x00007ff768897eda cc1_main(class llvm::ArrayRef<char const *>, char const *, void *) F:\llvm-project\clang\tools\driver\cc1_main.cpp:240:0
llvm/llvm-project#388 0x00007ff768894f03 ExecuteCC1Tool F:\llvm-project\clang\tools\driver\driver.cpp:328:0
llvm/llvm-project#389 0x00007ff76a4bb536 llvm::function_ref<void ()>::callback_fn<`lambda at F:\llvm-project\clang\lib\Driver\Job.cpp:417:22'> F:\llvm-project\llvm\include\llvm\ADT\STLExtras.h:108:0
llvm/llvm-project#390 0x00007ff7690e5c02 llvm::CrashRecoveryContext::RunSafely(class llvm::function_ref<(void)>) F:\llvm-project\llvm\lib\Support\CrashRecoveryContext.cpp:228:0
llvm/llvm-project#391 0x00007ff76a4bae04 clang::driver::CC1Command::Execute(class llvm::ArrayRef<class llvm::Optional<class llvm::StringRef>>, class std::basic_string<char, struct std::char_traits<char>, class std::allocator<char>> *, bool *) const F:\llvm-project\clang\lib\Driver\Job.cpp:417:0
llvm/llvm-project#392 0x00007ff76921411f clang::driver::Compilation::ExecuteCommand(class clang::driver::Command const &, class clang::driver::Command const *&) const F:\llvm-project\clang\lib\Driver\Compilation.cpp:182:0
llvm/llvm-project#393 0x00007ff769214489 clang::driver::Compilation::ExecuteJobs(class clang::driver::JobList const &, class llvm::SmallVectorImpl<struct std::pair<int, class clang::driver::Command const *>> &) const F:\llvm-project\clang\lib\Driver\Compilation.cpp:233:0
llvm/llvm-project#394 0x00007ff769228ed7 clang::driver::Driver::ExecuteCompilation(class clang::driver::Compilation &, class llvm::SmallVectorImpl<struct std::pair<int, class clang::driver::Command const *>> &) F:\llvm-project\clang\lib\Driver\Driver.cpp:1479:0
llvm/llvm-project#395 0x00007ff76889447e main F:\llvm-project\clang\tools\driver\driver.cpp:496:0
llvm/llvm-project#396 0x00007ff76d477bd0 __scrt_common_main_seh d:\agent\_work\5\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288:0
llvm/llvm-project#397 0x00007ffa8c407bd4 (C:\WINDOWS\System32\KERNEL32.DLL+0x17bd4)
llvm/llvm-project#398 0x00007ffa8db2ced1 (C:\WINDOWS\SYSTEM32\ntdll.dll+0x6ced1)
clang-cl: error: clang frontend command failed with exit code 70 (use -v to see invocation)

Reduced repro:

// ---- precomp.h
struct CD3DX12_DEFAULT {};
extern const __declspec(selectany) CD3DX12_DEFAULT D3D12_DEFAULT;

struct CD3DX12_CPU_DESCRIPTOR_HANDLE
{
  CD3DX12_CPU_DESCRIPTOR_HANDLE(CD3DX12_DEFAULT) { ptr = 0; }
  size_t ptr;
};

// ---- precomp.cpp
#include "precomp.h"

// ---- a.cpp
#include "precomp.h"

int main() {
  CD3DX12_CPU_DESCRIPTOR_HANDLE desc = CD3DX12_CPU_DESCRIPTOR_HANDLE(D3D12_DEFAULT);
  return desc.ptr;
}

Compile with:

$ clang-cl /Ycprecomp.h precomp.cpp /c
$ clang-cl /Yuprecomp.h a.cpp /c
(yields assert above)

I'm synced at 8b60ba7.
Clang was built with -DLLVM_ENABLE_ASSERTIONS=ON.

[1] https://github.com/microsoft/DirectX-Graphics-Samples/tree/master/Libraries/D3DX12

[llvmbot]

The bug does not occur with 9.0.0 RC5 which has assertions enabled.
Marking as a blocker for 10.0.0, feel free to judge of the priority of this issue.

[llvmbot]

Just to clarify: this occurs in the 10.0 release branch as well.

[zmodem]

Thanks for the reproducer!

Bisection points to this commit:

---

commit cbc9d22
Author: Luboš Luňák l.lunak@centrum.cz
Date: Sun Nov 3 21:15:03 2019 +0100

make -fmodules-codegen and -fmodules-debuginfo work also with PCHs

Allow to build PCH's (with -building-pch-with-obj and the extra .o file)
with -fmodules-codegen -fmodules-debuginfo to allow emitting shared code
into the extra .o file, similarly to how it works with modules. A bit of
a misnomer, but the underlying functionality is the same. This saves up
to 20% of build time here.

Differential Revision: https://reviews.llvm.org/D69778

---

Luboš, can you take a look?

[llunak]

https://reviews.llvm.org/D74846

And it's simple and straightforward enough so that there shouldn't be any problem backporting it to 10.0 if it's serious enough (I can't judge, I'm on Linux).

[zmodem]

https://reviews.llvm.org/D74846

And it's simple and straightforward enough so that there shouldn't be any
problem backporting it to 10.0 if it's serious enough (I can't judge, I'm on
Linux).

From the discussion on D74846 it sounds like not everything going on here is well understood.

I've reverted cbc9d22 on master in 7ea9a6e until it can be resolved properly.

The revert was also pushed to 10.x as a8684e9.