Assertion `!Unexpanded.empty() && "Unable to find unexpanded parameter packs"' failed.

[TheLartians]

I've been using the emsdk v1.39.20 for a while in some projects based on my ModernWasmStarter template, however, it seems when upgrading to any newer version, I'm getting an Assertion '!Unexpanded.empty() && "Unable to find unexpanded parameter packs"' failed. error.

I haven't had time yet to create a minimal reproducer, however I can easily get the error through building the subproject EmGlue. The error is reproducible on my local system and on GitHub Workflows.

Reproducer:

git clone https://github.com/TheLartians/EmGlue
emcmake cmake -HEmGlue -BEmGlue/build
cmake --build EmGlue/build

Full output

Cloning into 'EmGlue'...
remote: Enumerating objects: 195, done.
remote: Counting objects: 100% (195/195), done.
remote: Compressing objects: 100% (108/108), done.
remote: Total 195 (delta 78), reused 124 (delta 45), pack-reused 0
Receiving objects: 100% (195/195), 47.87 KiB | 11.97 MiB/s, done.
Resolving deltas: 100% (78/78), done.
configure: cmake -HEmGlue -BEmGlue/build -DCMAKE_TOOLCHAIN_FILE=/Users/lars/Documents/Development/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -DCMAKE_CROSSCOMPILING_EMULATOR="/Users/lars/Documents/Development/emsdk/node/12.18.1_64bit/bin/node"
-- CPM: adding package Glue@1.3.4 (/Users/lars/.cache/CPM/glue/9889420029a83e7f018adb91aa03c01fc95176f5)
-- CPM: Glue: adding package PackageProject.cmake@1.2 (/Users/lars/.cache/CPM/packageproject.cmake/647b2ccf5c064ff26832b4ada87e20395cd0ff2c)
-- CPM: Glue: adding package EasyIterator@1.4 (/Users/lars/.cache/CPM/easyiterator/034d91a47fb6cf2163274c9d60443f6cff409feb)
-- CPM: Glue: adding package Revisited@2.3 (/Users/lars/.cache/CPM/revisited/44808ea53e3e544d4b439e1b9088e66c24559b0e)
-- CPM: Glue: Revisited: adding package StaticTypeInfo@1.2 (/Users/lars/.cache/CPM/statictypeinfo/f50f96f1027af5f5ab4e5fe360882a633bf147bf)
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/lars/Documents/Development/test/EmGlue/build
Scanning dependencies of target Glue
[ 14%] Building CXX object _deps/glue-build/CMakeFiles/Glue.dir/source/anymap.cpp.o
Assertion failed: (!Unexpanded.empty() && "Unable to find unexpanded parameter packs"), function DiagnoseUnexpandedParameterPack, file /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/clang/lib/Sema/SemaTemplateVariadic.cpp, line 407.
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: /Users/lars/Documents/Development/emsdk/upstream/bin/clang++ -target wasm32-unknown-emscripten -D__EMSCRIPTEN_major__=1 -D__EMSCRIPTEN_minor__=40 -D__EMSCRIPTEN_tiny__=0 -D_LIBCPP_ABI_VERSION=2 -Dunix -D__unix -D__unix__ -Werror=implicit-function-declaration -Xclang -nostdsysteminc -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/include/libcxx -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/lib/libcxxabi/include -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/include/compat -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/include -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/include/libc -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/lib/libc/musl/arch/emscripten -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/local/include -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/include/SSE -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/lib/compiler-rt/include -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/lib/libunwind/include -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/cache/wasm/include -DEMSCRIPTEN -fignore-exceptions -I/Users/lars/.cache/CPM/glue/9889420029a83e7f018adb91aa03c01fc95176f5/include -I/Users/lars/.cache/CPM/easyiterator/034d91a47fb6cf2163274c9d60443f6cff409feb/include -I/Users/lars/.cache/CPM/revisited/44808ea53e3e544d4b439e1b9088e66c24559b0e/include -I/Users/lars/.cache/CPM/statictypeinfo/f50f96f1027af5f5ab4e5fe360882a633bf147bf/include -std=gnu++17 -c /Users/lars/.cache/CPM/glue/9889420029a83e7f018adb91aa03c01fc95176f5/source/anymap.cpp -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/include/SDL -c -o CMakeFiles/Glue.dir/source/anymap.cpp.o -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr 
1.	/Users/lars/.cache/CPM/revisited/44808ea53e3e544d4b439e1b9088e66c24559b0e/include/revisited/any_function.h:160:59: current parser token ')'
2.	/Users/lars/.cache/CPM/revisited/44808ea53e3e544d4b439e1b9088e66c24559b0e/include/revisited/any_function.h:12:1: parsing namespace 'revisited'
3.	/Users/lars/.cache/CPM/revisited/44808ea53e3e544d4b439e1b9088e66c24559b0e/include/revisited/any_function.h:117:3: parsing struct/union/class body 'revisited::AnyFunction'
4.	/Users/lars/.cache/CPM/revisited/44808ea53e3e544d4b439e1b9088e66c24559b0e/include/revisited/any_function.h:157:71: parsing function body 'revisited::AnyFunction::operator()'
5.	/Users/lars/.cache/CPM/revisited/44808ea53e3e544d4b439e1b9088e66c24559b0e/include/revisited/any_function.h:157:71: in compound statement ('{}')
6.	/Users/lars/.cache/CPM/revisited/44808ea53e3e544d4b439e1b9088e66c24559b0e/include/revisited/any_function.h:158:31: lambda expression parsing
7.	/Users/lars/.cache/CPM/revisited/44808ea53e3e544d4b439e1b9088e66c24559b0e/include/revisited/any_function.h:158:37: in compound statement ('{}')
0  libLLVM.dylib            0x000000010e4cacb5 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 37
1  libLLVM.dylib            0x000000010e4c9b38 llvm::sys::RunSignalHandlers() + 248
2  libLLVM.dylib            0x000000010e4ca170 llvm::sys::CleanupOnSignal(unsigned long) + 208
3  libLLVM.dylib            0x000000010e3e68ca (anonymous namespace)::CrashRecoveryContextImpl::HandleCrash(int, unsigned long) + 106
4  libLLVM.dylib            0x000000010e3e6a5d CrashRecoverySignalHandler(int) + 109
5  libsystem_platform.dylib 0x00007fff6b34f5fd _sigtramp + 29
6  libclang-cpp.dylib       0x0000000113de4cab UnoptArrays + 273531
7  libsystem_c.dylib        0x00007fff6b225808 abort + 120
8  libsystem_c.dylib        0x00007fff6b224ac6 err + 0
9  libclang-cpp.dylib       0x0000000112753c9e clang::Sema::DiagnoseUnexpandedParameterPack(clang::Expr*, clang::Sema::UnexpandedParameterPackContext) + 206
10 libclang-cpp.dylib       0x0000000112395e07 clang::Sema::ActOnFinishFullExpr(clang::Expr*, clang::SourceLocation, bool, bool) + 71
11 libclang-cpp.dylib       0x00000001122dfb1a clang::Sema::ActOnCondition(clang::Scope*, clang::SourceLocation, clang::Expr*, clang::Sema::ConditionKind) + 346
12 libclang-cpp.dylib       0x000000011188dc02 clang::Parser::ParseCXXCondition(clang::ActionResult<clang::Stmt*, true>*, clang::SourceLocation, clang::Sema::ConditionKind, clang::Parser::ForRangeInfo*) + 3042
13 libclang-cpp.dylib       0x00000001118d938b clang::Parser::ParseParenExprOrCondition(clang::ActionResult<clang::Stmt*, true>*, clang::Sema::ConditionResult&, clang::SourceLocation, clang::Sema::ConditionKind, clang::SourceLocation*, clang::SourceLocation*) + 283
14 libclang-cpp.dylib       0x00000001118d3714 clang::Parser::ParseIfStatement(clang::SourceLocation*) + 612
15 libclang-cpp.dylib       0x00000001118d058b clang::Parser::ParseStatementOrDeclarationAfterAttributes(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*, clang::Parser::ParsedAttributesWithRange&) + 2251
16 libclang-cpp.dylib       0x00000001118cfaac clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) + 204
17 libclang-cpp.dylib       0x00000001118d8be0 clang::Parser::ParseCompoundStatementBody(bool) + 1920
18 libclang-cpp.dylib       0x000000011188a30b clang::Parser::ParseLambdaExpressionAfterIntroducer(clang::LambdaIntroducer&) + 6139
19 libclang-cpp.dylib       0x00000001118876c0 clang::Parser::ParseLambdaExpression() + 208
20 libclang-cpp.dylib       0x000000011187468d clang::Parser::ParseCastExpression(clang::Parser::CastParseKind, bool, bool&, clang::Parser::TypeCastState, bool, bool*) + 8045
21 libclang-cpp.dylib       0x000000011186e56e clang::Parser::ParseAssignmentExpression(clang::Parser::TypeCastState) + 174
22 libclang-cpp.dylib       0x0000000111895f87 clang::Parser::ParseBraceInitializer() + 711
23 libclang-cpp.dylib       0x0000000111895f70 clang::Parser::ParseBraceInitializer() + 688
24 libclang-cpp.dylib       0x000000011184137e clang::Parser::ParseDeclarationAfterDeclaratorAndAttributes(clang::Declarator&, clang::Parser::ParsedTemplateInfo const&, clang::Parser::ForRangeInit*) + 4446
25 libclang-cpp.dylib       0x000000011183e050 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::SourceLocation*, clang::Parser::ForRangeInit*) + 2400
26 libclang-cpp.dylib       0x0000000111838942 clang::Parser::ParseSimpleDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&, bool, clang::Parser::ForRangeInit*, clang::SourceLocation*) + 546
27 libclang-cpp.dylib       0x0000000111838258 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&, clang::SourceLocation*) + 440
28 libclang-cpp.dylib       0x00000001118d00ce clang::Parser::ParseStatementOrDeclarationAfterAttributes(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*, clang::Parser::ParsedAttributesWithRange&) + 1038
29 libclang-cpp.dylib       0x00000001118cfaac clang::Parser::ParseStatementOrDeclaration(llvm::SmallVector<clang::Stmt*, 32u>&, clang::Parser::ParsedStmtContext, clang::SourceLocation*) + 204
30 libclang-cpp.dylib       0x00000001118d8be0 clang::Parser::ParseCompoundStatementBody(bool) + 1920
31 libclang-cpp.dylib       0x00000001118d9b4c clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&) + 172
32 libclang-cpp.dylib       0x000000011182b8fe clang::Parser::ParseLexedMethodDef(clang::Parser::LexedMethod&) + 734
33 libclang-cpp.dylib       0x000000011182a4ca clang::Parser::ParseLexedMethodDefs(clang::Parser::ParsingClass&) + 186
34 libclang-cpp.dylib       0x00000001118601d6 clang::Parser::ParseCXXMemberSpecification(clang::SourceLocation, clang::SourceLocation, clang::Parser::ParsedAttributesWithRange&, unsigned int, clang::Decl*) + 2598
35 libclang-cpp.dylib       0x000000011185da85 clang::Parser::ParseClassSpecifier(clang::tok::TokenKind, clang::SourceLocation, clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, bool, clang::Parser::DeclSpecContext, clang::Parser::ParsedAttributesWithRange&) + 6197
36 libclang-cpp.dylib       0x0000000111838f12 clang::Parser::ParseDeclarationSpecifiers(clang::DeclSpec&, clang::Parser::ParsedTemplateInfo const&, clang::AccessSpecifier, clang::Parser::DeclSpecContext, clang::Parser::LateParsedAttrList*) + 1074
37 libclang-cpp.dylib       0x00000001118f6017 clang::Parser::ParseDeclOrFunctionDefInternal(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec&, clang::AccessSpecifier) + 135
38 libclang-cpp.dylib       0x00000001118f5d12 clang::Parser::ParseDeclarationOrFunctionDefinition(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*, clang::AccessSpecifier) + 642
39 libclang-cpp.dylib       0x00000001118f4382 clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*) + 2450
40 libclang-cpp.dylib       0x0000000111856559 clang::Parser::ParseInnerNamespace(llvm::SmallVector<clang::Parser::InnerNamespaceInfo, 4u> const&, unsigned int, clang::SourceLocation&, clang::ParsedAttributes&, clang::BalancedDelimiterTracker&) + 281
41 libclang-cpp.dylib       0x0000000111855df4 clang::Parser::ParseNamespace(clang::DeclaratorContext, clang::SourceLocation&, clang::SourceLocation) + 6036
42 libclang-cpp.dylib       0x0000000111838402 clang::Parser::ParseDeclaration(clang::DeclaratorContext, clang::SourceLocation&, clang::Parser::ParsedAttributesWithRange&, clang::SourceLocation*) + 866
43 libclang-cpp.dylib       0x00000001118f3aae clang::Parser::ParseExternalDeclaration(clang::Parser::ParsedAttributesWithRange&, clang::ParsingDeclSpec*) + 190
44 libclang-cpp.dylib       0x00000001118f22a6 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<clang::DeclGroupRef>&, bool) + 1766
45 libclang-cpp.dylib       0x0000000111826a1d clang::ParseAST(clang::Sema&, bool, bool) + 509
46 libclang-cpp.dylib       0x000000011329d663 clang::FrontendAction::Execute() + 99
47 libclang-cpp.dylib       0x00000001132347b4 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) + 2324
48 libclang-cpp.dylib       0x0000000113310b15 clang::ExecuteCompilerInvocation(clang::CompilerInstance*) + 1509
49 clang++                  0x000000010e3379d1 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) + 1985
50 clang++                  0x000000010e335938 ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&) + 344
51 libclang-cpp.dylib       0x0000000112edb227 void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<llvm::Optional<llvm::StringRef> >, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >*, bool*) const::$_1>(long) + 23
52 libLLVM.dylib            0x000000010e3e67dc llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) + 236
53 libclang-cpp.dylib       0x0000000112eda587 clang::driver::CC1Command::Execute(llvm::ArrayRef<llvm::Optional<llvm::StringRef> >, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >*, bool*) const + 375
54 libclang-cpp.dylib       0x0000000112ea83ad clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&) const + 397
55 libclang-cpp.dylib       0x0000000112ea880d clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::__1::pair<int, clang::driver::Command const*> >&) const + 125
56 libclang-cpp.dylib       0x0000000112ec18dc clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::__1::pair<int, clang::driver::Command const*> >&) + 396
57 clang++                  0x000000010e33524f main + 10575
58 libdyld.dylib            0x00007fff6b156cc9 start + 1
clang-12: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 12.0.0 (/b/s/w/ir/cache/git/chromium.googlesource.com-external-github.tiyicn.workers.dev-llvm-llvm--project 13a3d88666e2162a91dfcae3824198c9ba74cc7b)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /Users/lars/Documents/Development/emsdk/upstream/bin
clang-12: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang-12: note: diagnostic msg: /var/folders/_d/fdgm1zz15533c569yh24jlsh0000gn/T/anymap-26f670.cpp
clang-12: note: diagnostic msg: /var/folders/_d/fdgm1zz15533c569yh24jlsh0000gn/T/anymap-26f670.sh
clang-12: note: diagnostic msg: Crash backtrace is located in
clang-12: note: diagnostic msg: /Users/lars/Library/Logs/DiagnosticReports/clang-12_<YYYY-MM-DD-HHMMSS>_<hostname>.crash
clang-12: note: diagnostic msg: (choose the .crash file that corresponds to your crash)
clang-12: note: diagnostic msg: 

********************
em++: error: '/Users/lars/Documents/Development/emsdk/upstream/bin/clang++ -target wasm32-unknown-emscripten -D__EMSCRIPTEN_major__=1 -D__EMSCRIPTEN_minor__=40 -D__EMSCRIPTEN_tiny__=0 -D_LIBCPP_ABI_VERSION=2 -Dunix -D__unix -D__unix__ -Werror=implicit-function-declaration -Xclang -nostdsysteminc -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/include/libcxx -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/lib/libcxxabi/include -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/include/compat -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/include -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/include/libc -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/lib/libc/musl/arch/emscripten -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/local/include -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/include/SSE -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/lib/compiler-rt/include -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/lib/libunwind/include -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/cache/wasm/include -DEMSCRIPTEN -fignore-exceptions -I/Users/lars/.cache/CPM/glue/9889420029a83e7f018adb91aa03c01fc95176f5/include -I/Users/lars/.cache/CPM/easyiterator/034d91a47fb6cf2163274c9d60443f6cff409feb/include -I/Users/lars/.cache/CPM/revisited/44808ea53e3e544d4b439e1b9088e66c24559b0e/include -I/Users/lars/.cache/CPM/statictypeinfo/f50f96f1027af5f5ab4e5fe360882a633bf147bf/include -std=gnu++17 -c /Users/lars/.cache/CPM/glue/9889420029a83e7f018adb91aa03c01fc95176f5/source/anymap.cpp -Xclang -isystem/Users/lars/Documents/Development/emsdk/upstream/emscripten/system/include/SDL -c -o CMakeFiles/Glue.dir/source/anymap.cpp.o -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr' failed (254)
make[2]: *** [_deps/glue-build/CMakeFiles/Glue.dir/source/anymap.cpp.o] Error 1
make[1]: *** [_deps/glue-build/CMakeFiles/Glue.dir/all] Error 2
make: *** [all] Error 2

My current workaround is to continue working with a lower version, however it would be nice to be able to upgrade eventually. Let me know if I can provide further info.

[sbc100]

It looks like a crash in the C++ front end compiler, perhaps unrelated to emscripten.

Can you follow the instructions under PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT and attache thong files?

[TheLartians]

Good point, I've added the preprocessed source and associated run script files to the zip below. Unfortunately, I could not find the crash backtrace as described in the location, though I hope the log above contains enough information. The crash happened with version 1.40.0 (though it seems to be identical to the one when using latest).

report.zip

I agree that it looks like it's related to the version of clang bundled with Emscripten. Is this just a normal clang build? Is it possible to override the version of clang that Emscripten uses?

[sbc100]

Yes you can modify LLVM_ROOT in your .emscripten or set EM_LLVM_ROOT in your environment to override the LLVM/clang used. However emscripten generally requires the latest version of llvm/clang.

[TheLartians]

Yeah, so I've tried to use emscripten with the latest official release of LLVM (10.0.1), and as you said it couldn't build the project as emscripten seems to require version 12.0.0. I think I'll stick with Emscripten v1.39.20 for now and see if I can test with LLVM 12 eventually.

[kripken]

If this happens on latest emscripten then it's also still a bug on LLVM trunk (as of a few days ago), so it would be good to file an upstream LLVM issue with that report.zip, unless I'm missing something @sbc100 ?

[sbc100]

yeah it sounds like an llvm bug..I was thinking it might be good to confirm its not specific with --target=emscripten.. but its an llvm bug either way so yeah upstream bug makes sense.

[stale]

This issue has been automatically marked as stale because there has been no activity in the past year. It will be closed automatically if no further activity occurs in the next 30 days. Feel free to re-open at any time if this issue is still relevant.

[TheLartians]

The issue seems to be fixed in emsdk version 2.0.31, and the code now builds without errors! 🎉