[crash] fatal error: too many errors emitted, stopping now

```
[2/3] Building CXX object src/test/CMakeFiles/test_bitcoin.dir/metaindex_btc_tests.cpp.o
FAILED: src/test/CMakeFiles/test_bitcoin.dir/metaindex_btc_tests.cpp.o
ccache /usr/bin/ccache /usr/bin/clang++-21 -DBOOST_ALL_NO_LIB -DBOOST_MULTI_INDEX_DISABLE_SERIALIZATION -DBOOST_NO_CXX98_FUNCTION_BASE -I/home/oleg/Projects/indexer/build/src -I/home/oleg/Projects/indexer/src -I/home/oleg/Projects/indexer/src/univalue/include -I/home/oleg/Projects/indexer/src/minisketch/include -I/home/oleg/Projects/indexer/src/secp256k1/include -O2 -g -std=c++23 -fPIE -fdebug-prefix-map=/home/oleg/Projects/indexer/src=. -fmacro-prefix-map=/home/oleg/Projects/indexer/src=. -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=3 -Wstack-protector -fstack-protector-all -fcf-protection=full -fstack-clash-protection -Wall -Wextra -Wgnu -Wformat -Wformat-security -Wvla -Wshadow-field -Wthread-safety -Wthread-safety-pointer -Wloop-analysis -Wredundant-decls -Wunused-member-function -Wdate-time -Wconditional-uninitialized -Woverloaded-virtual -Wsuggest-override -Wimplicit-fallthrough -Wunreachable-code -Wdocumentation -Wself-assign -Wundef -Wno-unused-parameter -MD -MT src/test/CMakeFiles/test_bitcoin.dir/metaindex_btc_tests.cpp.o -MF src/test/CMakeFiles/test_bitcoin.dir/metaindex_btc_tests.cpp.o.d -o src/test/CMakeFiles/test_bitcoin.dir/metaindex_btc_tests.cpp.o -c /home/oleg/Projects/indexer/src/test/metaindex_btc_tests.cpp
:1:2: warning: null character ignored [-Wnull-character]
1 | # 1 "" 3
| ^
:67:18: error: source file is not valid UTF-8
67 | #define __cpp_digit_separators 201309L
| ^
:67:19: error: source file is not valid UTF-8
67 | #define __cpp_digit_separators 201309L
| ^
:67:17: error: unknown type name 'P'
67 | #define __cpp_digit_separators 201309L
| ^
:67:20: error: expected unqualified-id
67 | #define __cpp_digit_separators 201309L
| ^
:67:27: error: source file is not valid UTF-8
67 | #define __cpp_digit_separators 201309L
| ^
:68:3: error: source file is not valid UTF-8
68 | #define __cpp_init_captures 201803L
| ^
:68:4: error: source file is not valid UTF-8
68 | #define __cpp_init_captures 201803L
| ^
:69:22: error: source file is not valid UTF-8
69 | #define __cpp_generic_lambdas 201707L
| ^
:69:23: error: source file is not valid UTF-8
69 | #define __cpp_generic_lambdas 201707L
| ^
:69:24: error: source file is not valid UTF-8
69 | #define __cpp_generic_lambdas 201707L
| ^
:69:32: error: source file is not valid UTF-8
69 | #define __cpp_generic_lambdas 201707L
| ^
:70:9: error: source file is not valid UTF-8
70 | #define __cpp_decltype_auto 201304L
| ^
:70:10: error: source file is not valid UTF-8
70 | #define __cpp_decltype_auto 201304L
| ^
:71:28: error: source file is not valid UTF-8
71 | #define __cpp_return_type_deduction 201304L
| ^
:71:29: error: source file is not valid UTF-8
71 | #define __cpp_return_type_deduction 201304L
| ^
:71:30: error: source file is not valid UTF-8
71 | #define __cpp_return_type_deduction 201304L
| ^
:71:38: error: source file is not valid UTF-8
71 | #define __cpp_return_type_deduction 201304L
| ^
:72:9: error: source file is not valid UTF-8
72 | #define __cpp_aggregate_nsdmi 201304L
| ^
:72:10: error: source file is not valid UTF-8
72 | #define __cpp_aggregate_nsdmi 201304L
| ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0. Program arguments: /usr/bin/clang++-21 -O2 -g -std=c++23 -fPIE -fdebug-prefix-map=/home/oleg/Projects/indexer/src=. -fmacro-prefix-map=/home/oleg/Projects/indexer/src=. -Wstack-protector -fstack-protector-all -fcf-protection=full -fstack-clash-protection -Wall -Wextra -Wgnu -Wformat -Wformat-security -Wvla -Wshadow-field -Wthread-safety -Wthread-safety-pointer -Wloop-analysis -Wredundant-decls -Wunused-member-function -Wdate-time -Wconditional-uninitialized -Woverloaded-virtual -Wsuggest-override -Wimplicit-fallthrough -Wunreachable-code -Wdocumentation -Wself-assign -Wundef -Wno-unused-parameter -DBOOST_ALL_NO_LIB -DBOOST_MULTI_INDEX_DISABLE_SERIALIZATION -DBOOST_NO_CXX98_FUNCTION_BASE -I/home/oleg/Projects/indexer/build/src -I/home/oleg/Projects/indexer/src -I/home/oleg/Projects/indexer/src/univalue/include -I/home/oleg/Projects/indexer/src/minisketch/include -I/home/oleg/Projects/indexer/src/secp256k1/include -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=3 -c -MD -MT src/test/CMakeFiles/test_bitcoin.dir/metaindex_btc_tests.cpp.o -MF src/test/CMakeFiles/test_bitcoin.dir/metaindex_btc_tests.cpp.o.d -fcolor-diagnostics -o src/test/CMakeFiles/test_bitcoin.dir/metaindex_btc_tests.cpp.o /home/oleg/Projects/indexer/src/test/metaindex_btc_tests.cpp
1. parser at unknown location
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0 libLLVM.so.21.0 0x000071592a3b88f6 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 54
1 libLLVM.so.21.0 0x000071592a3b61a3 llvm::sys::RunSignalHandlers() + 131
2 libLLVM.so.21.0 0x000071592a2f6680
3 libc.so.6 0x0000715929042520
4 libclang-cpp.so.21.0 0x000071593290ad05 clang::Lexer::SkipWhitespace(clang::Token&, char const*, bool&) + 37
5 libclang-cpp.so.21.0 0x000071593290e46c clang::Lexer::LexTokenInternal(clang::Token&, bool) + 1692
6 libclang-cpp.so.21.0 0x0000715932974ddd clang::Preprocessor::Lex(clang::Token&) + 61
7 libclang-cpp.so.21.0 0x0000715932982c39
8 libclang-cpp.so.21.0 0x0000715932a3a6d1 clang::Parser::SkipUntil(llvm::ArrayRef, clang::Parser::SkipUntilFlags) + 1041
9 libclang-cpp.so.21.0 0x0000715932a3a5be clang::Parser::SkipUntil(llvm::ArrayRef, clang::Parser::SkipUntilFlags) + 766
10 libclang-cpp.so.21.0 0x0000715932a3a5be clang::Parser::SkipUntil(llvm::ArrayRef, clang::Parser::SkipUntilFlags) + 766
11 libclang-cpp.so.21.0 0x0000715932992206 clang::Parser::SkipMalformedDecl() + 310
12 libclang-cpp.so.21.0 0x00007159329910a6 clang::Parser::ParseDeclGroup(clang::ParsingDeclSpec&, clang::DeclaratorContext, clang::ParsedAttributes&, clang::Parser::ParsedTemplateInfo&, clang::SourceLocation*, clang::Parser::ForRangeInit*) + 2502
13 libclang-cpp.so.21.0 0x0000715932a3e88f clang::Parser::ParseDeclOrFunctionDefInternal(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec&, clang::AccessSpecifier) + 1055
14 libclang-cpp.so.21.0 0x0000715932a3e28e clang::Parser::ParseDeclarationOrFunctionDefinition(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*, clang::AccessSpecifier) + 590
15 libclang-cpp.so.21.0 0x0000715932a3d591 clang::Parser::ParseExternalDeclaration(clang::ParsedAttributes&, clang::ParsedAttributes&, clang::ParsingDeclSpec*) + 2081
16 libclang-cpp.so.21.0 0x0000715932a3bdc7 clang::Parser::ParseTopLevelDecl(clang::OpaquePtr&, clang::Sema::ModuleImportState&) + 1287
17 libclang-cpp.so.21.0 0x000071593297cb4e clang::ParseAST(clang::Sema&, bool, bool) + 798
18 libclang-cpp.so.21.0 0x000071593459539b clang::FrontendAction::Execute() + 43
19 libclang-cpp.so.21.0 0x0000715934508cc4 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) + 948
20 libclang-cpp.so.21.0 0x000071593461b49e clang::ExecuteCompilerInvocation(clang::CompilerInstance*) + 702
21 clang++-21 0x00005b8c72b569ab cc1_main(llvm::ArrayRef, char const*, void*) + 6459
22 clang++-21 0x00005b8c72b53595
23 libclang-cpp.so.21.0 0x00007159341d3079
24 libLLVM.so.21.0 0x000071592a2f6348 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref) + 136
25 libclang-cpp.so.21.0 0x00007159341d29fd clang::driver::CC1Command::Execute(llvm::ArrayRef>, std::__cxx11::basic_string, std::allocator>*, bool*) const + 365
26 libclang-cpp.so.21.0 0x0000715934195dae clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const + 494
27 libclang-cpp.so.21.0 0x0000715934195f6e clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl>&, bool) const + 142
28 libclang-cpp.so.21.0 0x00007159341b4bed clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl>&) + 365
29 clang++-21 0x00005b8c72b5307a clang_main(int, char**, llvm::ToolContext const&) + 6410
30 clang++-21 0x00005b8c72b60b26 main + 102
31 libc.so.6 0x0000715929029d90
32 libc.so.6 0x0000715929029e40 __libc_start_main + 128
33 clang++-21 0x00005b8c72b512e5 _start + 37
clang++-21: error: clang frontend command failed with exit code 135 (use -v to see invocation)
Ubuntu clang version 21.0.0 (++20250708042308+dcf485609c5c-1~exp1~20250708162410.2527)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm-21/bin
clang++-21: note: diagnostic msg:
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang++-21: note: diagnostic msg: /tmp/metaindex_btc_tests-d2f4de.cpp
clang++-21: note: diagnostic msg: /tmp/metaindex_btc_tests-d2f4de.sh
clang++-21: note: diagnostic msg:
```

[metaindex_btc_tests-d2f4de.sh](https://github.com/user-attachments/files/22974383/metaindex_btc_tests-d2f4de.sh)
[metaindex_btc_tests-d2f4de.cpp](https://github.com/user-attachments/files/22974382/metaindex_btc_tests-d2f4de.cpp)

Start by running metaindex_btc_tests-d2f4de.sh against the attached metaindex_btc_tests-d2f4de.cpp with clang++-21, then compare the failure and stack trace with the reported crash. Read the compiler lexer and parser locations shown in the trace. Done means the attached reproduction no longer causes the fatal frontend crash and the behavior is covered appropriately.

Written by the indexing model from the issue text.