[clangd] Crash inside `clang::ASTDeclWriter::VisitTemplateTypeParmDecl`

[Equidamoid]

I'm getting the following crash when feeding clangd a compile_commands.json file generated for a esp32 cross-compilation build (not sure if it's relevant, the expected behaviour is still not to crash, regardless of the build parameters):

I[15:00:10.610] <-- textDocument/documentHighlight(14)
V[15:00:10.906] <<< {"id":15,"jsonrpc":"2.0","method":"textDocument/codeAction","params":{"context":{"diagnostics":[]},"range":{"end":{"character":0,"line":0},"start":{"character":0,"line":0}},"textDocument":{"uri":"file:///home/build/src/main.cpp"}}}

I[15:00:10.906] <-- textDocument/codeAction(15)
clangd: /var/tmp/portage/sys-devel/clang-19.0.0.9999/work/clang/lib/Serialization/ASTWriterDecl.cpp:1886: void clang::ASTDeclWriter::VisitTemplateTypeParmDecl(clang::TemplateTypeParmDecl*): Assertion `(bool)TC == D->hasTypeConstraint()' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	<eof> parser at end of file
1.	/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/bits/stl_iterator.h:2676:34: serializing '_It2'
 #0 0x00007f0f9e7adb75 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/usr/lib/llvm/19/bin/../lib64/libLLVM.so.19.0git7a935089+0x11c7b75)
 #1 0x00007f0f9e7aaeaf llvm::sys::RunSignalHandlers() (/usr/lib/llvm/19/bin/../lib64/libLLVM.so.19.0git7a935089+0x11c4eaf)
 #2 0x00007f0f9e7ab036 (/usr/lib/llvm/19/bin/../lib64/libLLVM.so.19.0git7a935089+0x11c5036)
 #3 0x00007f0f9d09d960 (/lib64/libc.so.6+0x3c960)
 #4 0x00007f0f9d0ef26c (/lib64/libc.so.6+0x8e26c)
 #5 0x00007f0f9d09d8b6 raise (/lib64/libc.so.6+0x3c8b6)
 #6 0x00007f0f9d0858b7 abort (/lib64/libc.so.6+0x248b7)
 #7 0x00007f0f9d0857db (/lib64/libc.so.6+0x247db)
 #8 0x00007f0f9d095eb6 (/lib64/libc.so.6+0x34eb6)
 #9 0x00007f0faaa2dc44 clang::ASTDeclWriter::VisitTemplateTypeParmDecl(clang::TemplateTypeParmDecl*) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33b3c44)
#10 0x00007f0faaa34453 clang::ASTDeclWriter::Visit(clang::Decl*) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33ba453)
#11 0x00007f0faaa34891 clang::ASTWriter::WriteDecl(clang::ASTContext&, clang::Decl*) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33ba891)
#12 0x00007f0faaa20762 clang::ASTWriter::WriteDeclAndTypes(clang::ASTContext&) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33a6762)
#13 0x00007f0faaa21725 clang::ASTWriter::WriteASTCore(clang::Sema&, llvm::StringRef, clang::Module*) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33a7725)
#14 0x00007f0faaa2276d clang::ASTWriter::WriteAST(clang::Sema&, llvm::StringRef, clang::Module*, llvm::StringRef, bool) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33a876d)
#15 0x00007f0faaa46c96 clang::PCHGenerator::HandleTranslationUnit(clang::ASTContext&) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33ccc96)
#16 0x00007f0faabdf202 (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x3565202)
#17 0x00007f0fa84862b5 clang::ParseAST(clang::Sema&, bool, bool) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0xe0c2b5)
#18 0x00007f0faab98e39 clang::FrontendAction::Execute() (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x351ee39)
#19 0x00007f0faabddd48 clang::PrecompiledPreamble::Build(clang::CompilerInvocation const&, llvm::MemoryBuffer const*, clang::PreambleBounds, clang::DiagnosticsEngine&, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>, std::shared_ptr<clang::PCHContainerOperations>, bool, llvm::StringRef, clang::PreambleCallbacks&) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x3563d48)
#20 0x00005652bbe2662a (/usr/lib/llvm/19/bin/clangd+0x51662a)
#21 0x00005652bbeb4ce9 (/usr/lib/llvm/19/bin/clangd+0x5a4ce9)
#22 0x00005652bbeb56f5 (/usr/lib/llvm/19/bin/clangd+0x5a56f5)
#23 0x00005652bc090d70 (/usr/lib/llvm/19/bin/clangd+0x780d70)
#24 0x00007f0f9d0ed551 (/lib64/libc.so.6+0x8c551)
#25 0x00007f0f9d15b92c (/lib64/libc.so.6+0xfa92c)
Signalled while building preamble
  Filename: /home/build/src/main.cpp
  Directory: /home/build/src/build-esp32-s2
  Command Line: /home/build/.espressif/tools/xtensa-esp32s2-elf/esp-12.2.0_20230208/xtensa-esp32s2-elf/bin/xtensa-esp32s2-elf-g++ --driver-mode=g++ -DGPIO_NUM_22=GPIO_NUM_MAX -DMBEDTLS_CONFIG_FILE="mbedtls/esp_config.h" -DSOC_MMU_PAGE_SIZE=CONFIG_MMU_PAGE_SIZE <include paths truncated> -mlongcalls -g -fdiagnostics-color=always -std=gnu++17 -fcoroutines -fconcepts -std=c++23 -o CMakeFiles/blink.elf.dir/src/main.cpp.obj -c -resource-dir=/usr/lib/llvm/19/bin/../../../../lib/clang/19 -- /home/build/src/main.cpp

clangd version 19.0.0git7a935089
Features: linux+debug
Platform: x86_64-pc-linux-gnu

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (Equidamoid)

I'm getting the following crash when feeding clangd a `compile_commands.json` file generated for a esp32 cross-compilation build (not sure if it's relevant, the expected behaviour is still not to crash, regardless of the build parameters):

I[15:00:10.610] <-- textDocument/documentHighlight(14)
V[15:00:10.906] <<< {"id":15,"jsonrpc":"2.0","method":"textDocument/codeAction","params":{"context":{"diagnostics":[]},"range":{"end":{"character":0,"line":0},"start":{"character":0,"line":0}},"textDocument":{"uri":"file:///home/build/src/main.cpp"}}}

I[15:00:10.906] <-- textDocument/codeAction(15)
clangd: /var/tmp/portage/sys-devel/clang-19.0.0.9999/work/clang/lib/Serialization/ASTWriterDecl.cpp:1886: void clang::ASTDeclWriter::VisitTemplateTypeParmDecl(clang::TemplateTypeParmDecl*): Assertion `(bool)TC == D->hasTypeConstraint()' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	<eof> parser at end of file
1.	/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/bits/stl_iterator.h:2676:34: serializing '_It2'
 #<!-- -->0 0x00007f0f9e7adb75 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/usr/lib/llvm/19/bin/../lib64/libLLVM.so.19.0git7a935089+0x11c7b75)
 #<!-- -->1 0x00007f0f9e7aaeaf llvm::sys::RunSignalHandlers() (/usr/lib/llvm/19/bin/../lib64/libLLVM.so.19.0git7a935089+0x11c4eaf)
 #<!-- -->2 0x00007f0f9e7ab036 (/usr/lib/llvm/19/bin/../lib64/libLLVM.so.19.0git7a935089+0x11c5036)
 #<!-- -->3 0x00007f0f9d09d960 (/lib64/libc.so.6+0x3c960)
 #<!-- -->4 0x00007f0f9d0ef26c (/lib64/libc.so.6+0x8e26c)
 #<!-- -->5 0x00007f0f9d09d8b6 raise (/lib64/libc.so.6+0x3c8b6)
 #<!-- -->6 0x00007f0f9d0858b7 abort (/lib64/libc.so.6+0x248b7)
 #<!-- -->7 0x00007f0f9d0857db (/lib64/libc.so.6+0x247db)
 #<!-- -->8 0x00007f0f9d095eb6 (/lib64/libc.so.6+0x34eb6)
 #<!-- -->9 0x00007f0faaa2dc44 clang::ASTDeclWriter::VisitTemplateTypeParmDecl(clang::TemplateTypeParmDecl*) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33b3c44)
#<!-- -->10 0x00007f0faaa34453 clang::ASTDeclWriter::Visit(clang::Decl*) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33ba453)
#<!-- -->11 0x00007f0faaa34891 clang::ASTWriter::WriteDecl(clang::ASTContext&amp;, clang::Decl*) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33ba891)
#<!-- -->12 0x00007f0faaa20762 clang::ASTWriter::WriteDeclAndTypes(clang::ASTContext&amp;) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33a6762)
#<!-- -->13 0x00007f0faaa21725 clang::ASTWriter::WriteASTCore(clang::Sema&amp;, llvm::StringRef, clang::Module*) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33a7725)
#<!-- -->14 0x00007f0faaa2276d clang::ASTWriter::WriteAST(clang::Sema&amp;, llvm::StringRef, clang::Module*, llvm::StringRef, bool) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33a876d)
#<!-- -->15 0x00007f0faaa46c96 clang::PCHGenerator::HandleTranslationUnit(clang::ASTContext&amp;) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33ccc96)
#<!-- -->16 0x00007f0faabdf202 (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x3565202)
#<!-- -->17 0x00007f0fa84862b5 clang::ParseAST(clang::Sema&amp;, bool, bool) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0xe0c2b5)
#<!-- -->18 0x00007f0faab98e39 clang::FrontendAction::Execute() (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x351ee39)
#<!-- -->19 0x00007f0faabddd48 clang::PrecompiledPreamble::Build(clang::CompilerInvocation const&amp;, llvm::MemoryBuffer const*, clang::PreambleBounds, clang::DiagnosticsEngine&amp;, llvm::IntrusiveRefCntPtr&lt;llvm::vfs::FileSystem&gt;, std::shared_ptr&lt;clang::PCHContainerOperations&gt;, bool, llvm::StringRef, clang::PreambleCallbacks&amp;) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x3563d48)
#<!-- -->20 0x00005652bbe2662a (/usr/lib/llvm/19/bin/clangd+0x51662a)
#<!-- -->21 0x00005652bbeb4ce9 (/usr/lib/llvm/19/bin/clangd+0x5a4ce9)
#<!-- -->22 0x00005652bbeb56f5 (/usr/lib/llvm/19/bin/clangd+0x5a56f5)
#<!-- -->23 0x00005652bc090d70 (/usr/lib/llvm/19/bin/clangd+0x780d70)
#<!-- -->24 0x00007f0f9d0ed551 (/lib64/libc.so.6+0x8c551)
#<!-- -->25 0x00007f0f9d15b92c (/lib64/libc.so.6+0xfa92c)
Signalled while building preamble
  Filename: /home/build/src/main.cpp
  Directory: /home/build/src/build-esp32-s2
  Command Line: /home/build/.espressif/tools/xtensa-esp32s2-elf/esp-12.2.0_20230208/xtensa-esp32s2-elf/bin/xtensa-esp32s2-elf-g++ --driver-mode=g++ -DGPIO_NUM_22=GPIO_NUM_MAX -DMBEDTLS_CONFIG_FILE="mbedtls/esp_config.h" -DSOC_MMU_PAGE_SIZE=CONFIG_MMU_PAGE_SIZE &lt;include paths truncated&gt; -mlongcalls -g -fdiagnostics-color=always -std=gnu++17 -fcoroutines -fconcepts -std=c++23 -o CMakeFiles/blink.elf.dir/src/main.cpp.obj -c -resource-dir=/usr/lib/llvm/19/bin/../../../../lib/clang/19 -- /home/build/src/main.cpp

clangd version 19.0.0git7a935089
Features: linux+debug
Platform: x86_64-pc-linux-gnu

[llvmbot]

@llvm/issue-subscribers-clangd

Author: None (Equidamoid)

I'm getting the following crash when feeding clangd a `compile_commands.json` file generated for a esp32 cross-compilation build (not sure if it's relevant, the expected behaviour is still not to crash, regardless of the build parameters):

I[15:00:10.610] <-- textDocument/documentHighlight(14)
V[15:00:10.906] <<< {"id":15,"jsonrpc":"2.0","method":"textDocument/codeAction","params":{"context":{"diagnostics":[]},"range":{"end":{"character":0,"line":0},"start":{"character":0,"line":0}},"textDocument":{"uri":"file:///home/build/src/main.cpp"}}}

I[15:00:10.906] <-- textDocument/codeAction(15)
clangd: /var/tmp/portage/sys-devel/clang-19.0.0.9999/work/clang/lib/Serialization/ASTWriterDecl.cpp:1886: void clang::ASTDeclWriter::VisitTemplateTypeParmDecl(clang::TemplateTypeParmDecl*): Assertion `(bool)TC == D->hasTypeConstraint()' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	<eof> parser at end of file
1.	/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/bits/stl_iterator.h:2676:34: serializing '_It2'
 #<!-- -->0 0x00007f0f9e7adb75 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/usr/lib/llvm/19/bin/../lib64/libLLVM.so.19.0git7a935089+0x11c7b75)
 #<!-- -->1 0x00007f0f9e7aaeaf llvm::sys::RunSignalHandlers() (/usr/lib/llvm/19/bin/../lib64/libLLVM.so.19.0git7a935089+0x11c4eaf)
 #<!-- -->2 0x00007f0f9e7ab036 (/usr/lib/llvm/19/bin/../lib64/libLLVM.so.19.0git7a935089+0x11c5036)
 #<!-- -->3 0x00007f0f9d09d960 (/lib64/libc.so.6+0x3c960)
 #<!-- -->4 0x00007f0f9d0ef26c (/lib64/libc.so.6+0x8e26c)
 #<!-- -->5 0x00007f0f9d09d8b6 raise (/lib64/libc.so.6+0x3c8b6)
 #<!-- -->6 0x00007f0f9d0858b7 abort (/lib64/libc.so.6+0x248b7)
 #<!-- -->7 0x00007f0f9d0857db (/lib64/libc.so.6+0x247db)
 #<!-- -->8 0x00007f0f9d095eb6 (/lib64/libc.so.6+0x34eb6)
 #<!-- -->9 0x00007f0faaa2dc44 clang::ASTDeclWriter::VisitTemplateTypeParmDecl(clang::TemplateTypeParmDecl*) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33b3c44)
#<!-- -->10 0x00007f0faaa34453 clang::ASTDeclWriter::Visit(clang::Decl*) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33ba453)
#<!-- -->11 0x00007f0faaa34891 clang::ASTWriter::WriteDecl(clang::ASTContext&amp;, clang::Decl*) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33ba891)
#<!-- -->12 0x00007f0faaa20762 clang::ASTWriter::WriteDeclAndTypes(clang::ASTContext&amp;) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33a6762)
#<!-- -->13 0x00007f0faaa21725 clang::ASTWriter::WriteASTCore(clang::Sema&amp;, llvm::StringRef, clang::Module*) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33a7725)
#<!-- -->14 0x00007f0faaa2276d clang::ASTWriter::WriteAST(clang::Sema&amp;, llvm::StringRef, clang::Module*, llvm::StringRef, bool) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33a876d)
#<!-- -->15 0x00007f0faaa46c96 clang::PCHGenerator::HandleTranslationUnit(clang::ASTContext&amp;) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x33ccc96)
#<!-- -->16 0x00007f0faabdf202 (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x3565202)
#<!-- -->17 0x00007f0fa84862b5 clang::ParseAST(clang::Sema&amp;, bool, bool) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0xe0c2b5)
#<!-- -->18 0x00007f0faab98e39 clang::FrontendAction::Execute() (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x351ee39)
#<!-- -->19 0x00007f0faabddd48 clang::PrecompiledPreamble::Build(clang::CompilerInvocation const&amp;, llvm::MemoryBuffer const*, clang::PreambleBounds, clang::DiagnosticsEngine&amp;, llvm::IntrusiveRefCntPtr&lt;llvm::vfs::FileSystem&gt;, std::shared_ptr&lt;clang::PCHContainerOperations&gt;, bool, llvm::StringRef, clang::PreambleCallbacks&amp;) (/usr/lib/llvm/19/bin/../lib64/libclang-cpp.so.19.0git7a935089+0x3563d48)
#<!-- -->20 0x00005652bbe2662a (/usr/lib/llvm/19/bin/clangd+0x51662a)
#<!-- -->21 0x00005652bbeb4ce9 (/usr/lib/llvm/19/bin/clangd+0x5a4ce9)
#<!-- -->22 0x00005652bbeb56f5 (/usr/lib/llvm/19/bin/clangd+0x5a56f5)
#<!-- -->23 0x00005652bc090d70 (/usr/lib/llvm/19/bin/clangd+0x780d70)
#<!-- -->24 0x00007f0f9d0ed551 (/lib64/libc.so.6+0x8c551)
#<!-- -->25 0x00007f0f9d15b92c (/lib64/libc.so.6+0xfa92c)
Signalled while building preamble
  Filename: /home/build/src/main.cpp
  Directory: /home/build/src/build-esp32-s2
  Command Line: /home/build/.espressif/tools/xtensa-esp32s2-elf/esp-12.2.0_20230208/xtensa-esp32s2-elf/bin/xtensa-esp32s2-elf-g++ --driver-mode=g++ -DGPIO_NUM_22=GPIO_NUM_MAX -DMBEDTLS_CONFIG_FILE="mbedtls/esp_config.h" -DSOC_MMU_PAGE_SIZE=CONFIG_MMU_PAGE_SIZE &lt;include paths truncated&gt; -mlongcalls -g -fdiagnostics-color=always -std=gnu++17 -fcoroutines -fconcepts -std=c++23 -o CMakeFiles/blink.elf.dir/src/main.cpp.obj -c -resource-dir=/usr/lib/llvm/19/bin/../../../../lib/clang/19 -- /home/build/src/main.cpp

clangd version 19.0.0git7a935089
Features: linux+debug
Platform: x86_64-pc-linux-gnu

[Endilll]

clangd log and stack trace alone are not nearly enough for us to reproduce this

[zyn0217]

@ChuanqiXu9 The assertion there is probably wrong. hasTypeConstraint() could be different with the value of getTypeConstraint() according to the document of TypeConstraintInitialized:

  /// Whether this template type parameter has a type-constraint construct.
  bool HasTypeConstraint : 1;

  /// Whether the type constraint has been initialized. This can be false if the
  /// constraint was not initialized yet or if there was an error forming the
  /// type constraint.
  bool TypeConstraintInitialized : 1;

[Equidamoid]

@Endilll unfortunately I wasn't able to reduce it to a nice reproduction scenario. I should be able to easily rebuild latest clang with any given patches and try reproducing the problem again though.

[falbrechtskirchinger]

I've been dealing with this crash for the past couple of weeks (19.1.0_rcX to git master today). Based on @zyn0217's hint, I tried a patch that initially worked, but with my limited understanding after reading the code for mere minutes, its correctness is doubtful. Especially, given that days later it crashed again in ASTReader::ReadStmtFromStream with ASTDeclReader::VisitTemplateTypeParmDecl making a suspicious appearance in the stack trace.

Thanks to #109354 I was reminded of C-Reduce et.al. and used C-Vise to create this unhelpful-looking reproducer:

test.hpp

#include <h>
#include <variant>

I tried a preprocessed version but that is evidently not the same as far as clangd is concerned.

compile_commands.json

[
{
  "directory": "/",
  "command": "/usr/bin/g++-14 -std=c++20",
  "file": "test.hpp"
}
]

Command line

/usr/lib/llvm/20/bin/clangd --compile-commands-dir=. --check=test.hpp

Output

I[17:36:59.185] clangd version 20.0.0git816134b3
I[17:36:59.185] Features: linux+debug
I[17:36:59.185] PID: 224952
I[17:36:59.185] Working directory: /volatile
I[17:36:59.185] argv[0]: /usr/lib/llvm/20/bin/clangd
I[17:36:59.185] argv[1]: --compile-commands-dir=.
I[17:36:59.185] argv[2]: --check=test.hpp
I[17:36:59.185] Entering check mode (no LSP server)
I[17:36:59.185] Testing on source file /volatile/test.hpp
I[17:36:59.185] Loading compilation database...
I[17:36:59.185] Loaded compilation database from /volatile/./compile_commands.json
I[17:36:59.186] Compile command inferred from test.hpp is: [/] /usr/x86_64-pc-linux-gnu/gcc-bin/14/g++-14 --driver-mode=g++ -std=c++20 -resource-dir=/usr/lib/llvm/20/bin/../../../../lib/clang/20 -- /volatile/test.hpp
I[17:36:59.186] Parsing command...
I[17:36:59.187] internal (cc1) args are: -cc1 -triple x86_64-pc-linux-gnu -fsyntax-only -disable-free -clear-ast-before-backend -main-file-name test.hpp -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fdebug-compilation-dir=/ -fcoverage-compilation-dir=/ -resource-dir /usr/lib/llvm/20/bin/../../../../lib/clang/20 -include /usr/include/gentoo/fortify.h -include /usr/include/gentoo/maybe-stddefs.h -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14 -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/x86_64-pc-linux-gnu -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/backward -internal-isystem /usr/lib/llvm/20/bin/../../../../lib/clang/20/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-pc-linux-gnu/14/../../../../x86_64-pc-linux-gnu/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -std=c++20 -fdeprecated-macro -ferror-limit 19 -stack-protector 2 -fstack-clash-protection -fcf-protection=full -fgnuc-version=4.2.1 -fno-implicit-modules -fskip-odr-check-in-gmf -fcxx-exceptions -fexceptions -no-round-trip-args -D__GCC_HAVE_DWARF2_CFI_ASM=1 -x c++-header /volatile/test.hpp
I[17:36:59.187] Building preamble...
clangd: /var/tmp/portage/sys-devel/clang-20.0.0.9999/work/clang/lib/Serialization/ASTWriterDecl.cpp:1890: void clang::ASTDeclWriter::VisitTemplateTypeParmDecl(clang::TemplateTypeParmDecl*): Assertion `(bool)TC == D->hasTypeConstraint()' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: /usr/lib/llvm/20/bin/clangd --compile-commands-dir=. --check=test.hpp
1.      <eof> parser at end of file
2.      /usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/iterator_concepts.h:798:32: serializing '_Iter'
 #0 0x00007fd6a5243fe0 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/usr/lib/llvm/20/bin/../lib64/libLLVM.so.20.0git816134b3+0xa43fe0)
 #1 0x00007fd6a5241294 llvm::sys::RunSignalHandlers() (/usr/lib/llvm/20/bin/../lib64/libLLVM.so.20.0git816134b3+0xa41294)
 #2 0x00007fd6a5241426 (/usr/lib/llvm/20/bin/../lib64/libLLVM.so.20.0git816134b3+0xa41426)
 #3 0x00007fd6a4250a50 (/usr/lib64/libc.so.6+0x3ca50)
 #4 0x00007fd6a42a621c (/usr/lib64/libc.so.6+0x9221c)
 #5 0x00007fd6a42509a6 raise (/usr/lib64/libc.so.6+0x3c9a6)
 #6 0x00007fd6a42388fa abort (/usr/lib64/libc.so.6+0x248fa)
 #7 0x00007fd6a423881e (/usr/lib64/libc.so.6+0x2481e)
 #8 0x00007fd6a4248f36 (/usr/lib64/libc.so.6+0x34f36)
 #9 0x00007fd6ad91617c clang::ASTDeclWriter::VisitTemplateTypeParmDecl(clang::TemplateTypeParmDecl*) (/usr/lib/llvm/20/bin/../lib64/libclang-cpp.so.20.0git816134b3+0x311617c)
#10 0x00007fd6ad91c863 clang::ASTDeclWriter::Visit(clang::Decl*) (/usr/lib/llvm/20/bin/../lib64/libclang-cpp.so.20.0git816134b3+0x311c863)
#11 0x00007fd6ad91cc97 clang::ASTWriter::WriteDecl(clang::ASTContext&, clang::Decl*) (/usr/lib/llvm/20/bin/../lib64/libclang-cpp.so.20.0git816134b3+0x311cc97)
#12 0x00007fd6ad9067d2 clang::ASTWriter::WriteDeclAndTypes(clang::ASTContext&) (/usr/lib/llvm/20/bin/../lib64/libclang-cpp.so.20.0git816134b3+0x31067d2)
#13 0x00007fd6ad907c07 clang::ASTWriter::WriteASTCore(clang::Sema&, llvm::StringRef, clang::Module*) (/usr/lib/llvm/20/bin/../lib64/libclang-cpp.so.20.0git816134b3+0x3107c07)
#14 0x00007fd6ad9090ae clang::ASTWriter::WriteAST(clang::Sema&, llvm::StringRef, clang::Module*, llvm::StringRef, bool) (/usr/lib/llvm/20/bin/../lib64/libclang-cpp.so.20.0git816134b3+0x31090ae)
#15 0x00007fd6ad92fcce clang::PCHGenerator::HandleTranslationUnit(clang::ASTContext&) (/usr/lib/llvm/20/bin/../lib64/libclang-cpp.so.20.0git816134b3+0x312fcce)
#16 0x00007fd6adad47c2 (/usr/lib/llvm/20/bin/../lib64/libclang-cpp.so.20.0git816134b3+0x32d47c2)
#17 0x00007fd6ab1c37dc clang::ParseAST(clang::Sema&, bool, bool) (/usr/lib/llvm/20/bin/../lib64/libclang-cpp.so.20.0git816134b3+0x9c37dc)
#18 0x00007fd6ada8a0e9 clang::FrontendAction::Execute() (/usr/lib/llvm/20/bin/../lib64/libclang-cpp.so.20.0git816134b3+0x328a0e9)
#19 0x00007fd6adad30fb clang::PrecompiledPreamble::Build(clang::CompilerInvocation const&, llvm::MemoryBuffer const*, clang::PreambleBounds, clang::DiagnosticsEngine&, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>, std::shared_ptr<clang::PCHContainerOperations>, bool, llvm::StringRef, clang::PreambleCallbacks&) (/usr/lib/llvm/20/bin/../lib64/libclang-cpp.so.20.0git816134b3+0x32d30fb)
#20 0x000055774c1254c8 (/usr/lib/llvm/20/bin/clangd+0x4b34c8)
#21 0x000055774bec2562 (/usr/lib/llvm/20/bin/clangd+0x250562)
#22 0x000055774bec4b5c (/usr/lib/llvm/20/bin/clangd+0x252b5c)
#23 0x000055774beb6c84 (/usr/lib/llvm/20/bin/clangd+0x244c84)
#24 0x00007fd6a423a42e (/usr/lib64/libc.so.6+0x2642e)
#25 0x00007fd6a423a4e9 __libc_start_main (/usr/lib64/libc.so.6+0x264e9)
#26 0x000055774be01a65 (/usr/lib/llvm/20/bin/clangd+0x18fa65)
Aborted

Let me know if there's anything else I can provide.