<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/96693>96693</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
Crash with assertion failure when compiling c++20 module
</td>
</tr>
<tr>
<th>Labels</th>
<td>
new issue
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
ottojo
</td>
</tr>
</table>
<pre>
I was playing around with C++20 modules and came across this crash when trying to include simdjson. Notably this only appeared when i switched to clang18, compilation under clang17 failed for other reason (without crash).
```
FAILED: Profiler/CMakeFiles/profilerLib.dir/modules/Scope.cppm.o Profiler/CMakeFiles/profilerLib.dir/profiler.scope.pcm
/opt/clang/18.1.8/bin/clang++ -DSIMDJSON_DISABLE_DEPRECATED_API=1 -DSIMDJSON_THREADS_ENABLED=1 -I/home/jonas/Workspace/ModuleTest/cmake-build-debug-clang-18/_deps/simdjson-src/include -g -std=gnu++20 -fcolor-diagnostics -Wall -Wextra -Wpedantic -MD -MT Profiler/CMakeFiles/profilerLib.dir/modules/Scope.cppm.o -MF Profiler/CMakeFiles/profilerLib.dir/modules/Scope.cppm.o.d @Profiler/CMakeFiles/profilerLib.dir/modules/Scope.cppm.o.modmap -o Profiler/CMakeFiles/profilerLib.dir/modules/Scope.cppm.o -c /home/jonas/Workspace/ModuleTest/Profiler/modules/Scope.cppm
clang-18: /home/jonas/.cache/yay/clang-prefixed-release/src/llvm-project-llvmorg-18.1.8/clang/include/clang/AST/Decl.h:4976: void clang::Redeclarable<clang::FunctionDecl>::setPreviousDecl(decl_type *) [decl_type = clang::FunctionDecl]: Assertion `!isa<NamedDecl>(static_cast<decl_type*>(this)) || cast<NamedDecl>(static_cast<decl_type*>(this))->isLinkageValid()' failed.
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: /opt/clang/18.1.8/bin/clang-18 -cc1 -triple x86_64-unknown-linux-gnu -emit-module-interface -disable-free -clear-ast-before-backend -main-file-name Scope.cppm -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 -debug-info-kind=constructor -dwarf-version=5 -debugger-tuning=gdb -fdebug-compilation-dir=/home/jonas/Workspace/ModuleTest/cmake-build-debug-clang-18 -fcoverage-compilation-dir=/home/jonas/Workspace/ModuleTest/cmake-build-debug-clang-18 -resource-dir /opt/clang/18.1.8/lib/clang/18 -dependency-file Profiler/CMakeFiles/profilerLib.dir/modules/Scope.cppm.o.d -MT Profiler/CMakeFiles/profilerLib.dir/modules/Scope.cppm.o -sys-header-deps -module-file-deps -D SIMDJSON_DISABLE_DEPRECATED_API=1 -D SIMDJSON_THREADS_ENABLED=1 -I /home/jonas/Workspace/ModuleTest/cmake-build-debug-clang-18/_deps/simdjson-src/include -internal-isystem /usr/lib64/gcc/x86_64-pc-linux-gnu/14.1.1/../../../../include/c++/14.1.1 -internal-isystem /usr/lib64/gcc/x86_64-pc-linux-gnu/14.1.1/../../../../include/c++/14.1.1/x86_64-pc-linux-gnu -internal-isystem /usr/lib64/gcc/x86_64-pc-linux-gnu/14.1.1/../../../../include/c++/14.1.1/backward -internal-isystem /opt/clang/18.1.8/lib/clang/18/include -internal-isystem /usr/local/include -internal-isystem /usr/lib64/gcc/x86_64-pc-linux-gnu/14.1.1/../../../../x86_64-pc-linux-gnu/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -Wall -Wextra -Wpedantic -std=gnu++20 -fdeprecated-macro -ferror-limit 19 -fgnuc-version=4.2.1 -fno-implicit-modules -fskip-odr-check-in-gmf -fcxx-exceptions -fexceptions -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o Profiler/CMakeFiles/profilerLib.dir/profiler.scope.pcm -x c++ /home/jonas/Workspace/ModuleTest/Profiler/modules/Scope.cppm
1. /home/jonas/Workspace/ModuleTest/cmake-build-debug-clang-18/_deps/simdjson-src/include/simdjson/generic/ondemand/token_iterator.h:136:222: current parser token ';'
2. /home/jonas/Workspace/ModuleTest/cmake-build-debug-clang-18/_deps/simdjson-src/include/simdjson/generic/ondemand/token_iterator.h:10:1: parsing namespace 'simdjson'
3. /home/jonas/Workspace/ModuleTest/cmake-build-debug-clang-18/_deps/simdjson-src/include/simdjson/generic/ondemand/token_iterator.h:11:1: parsing namespace 'simdjson::fallback'
4. /home/jonas/Workspace/ModuleTest/cmake-build-debug-clang-18/_deps/simdjson-src/include/simdjson/generic/ondemand/token_iterator.h:12:1: parsing namespace 'simdjson::fallback::ondemand'
5. /home/jonas/Workspace/ModuleTest/cmake-build-debug-clang-18/_deps/simdjson-src/include/simdjson/generic/ondemand/token_iterator.h:20:1: parsing struct/union/class body 'simdjson::fallback::ondemand::token_iterator'
#0 0x0000776d4e624767 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/clang/18.1.8/bin/../lib/libLLVM.so.18.1+0x3e24767)
clang++: error: unable to execute command: Aborted (core dumped)
clang++: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 18.1.8 (https://aur.archlinux.org/clang-prefixed-release.git 5b99959cda7596f74533734675cdc4796a2653c4)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/clang/18.1.8/bin
clang++: note: diagnostic msg:
********************
PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang++: note: diagnostic msg: /tmp/Scope-ed983e.cppm
clang++: note: diagnostic msg: /tmp/Scope-ed983e.sh
clang++: note: diagnostic msg:
********************
```
[Scope-ed983e.cppm.txt](https://github.com/user-attachments/files/15978031/Scope-ed983e.cppm.txt)
[Scope-ed983e.sh.txt](https://github.com/user-attachments/files/15978032/Scope-ed983e.sh.txt)
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzMWV9T27oS_zTiZUceR87fBx5CHJ9yB1qmcE8fM4q0dlRsySPJEL79HckmhAM9pS33nM4wJl5Jq13t6rd_zJ1TlUY8JZMzMslPeOd3xp4a781Xc7I18uH0HO65g7bmD0pXwK3ptIR75XewIuyMsDOWQmNkV6MDriUI3iBwYY1z4HfKgbDc7eB-hxq8jUy8AaVF3UkEpxr51RmdwEfj-bZ-6NcYXT8Ab1vkFmW_VoG7V17sUIb1oua6Gs0JW4EwTatq7pXR0GmJdhicQclVjRJKY8H4HVqwyJ3RQNg8KGA63wtH2CIhaU7S5fCcpsNffC2W5xfrnGRLuLKmVDVaworVJb_FQtXoCCvagX6htolUYXg4EcKKa2FaTETbNon5AQaPlMTF9a1oYBCOFab1hBVRS8KK0TwZJXPCiq3ST-RgGaD59fll_p_rTx83-fn18uxivcnXV5_Xq-XNOt8sr85Jlo-OZ918-Lxe5teb9ccwOe-HzwkrdqZBwoqvRvMg7xdjb13LRaBdRlVv0EWhGn6LdNupWlKJ266iUR4aTFVsJLZh9aPRqbOCsOLRF2gF1HlJsrzS3cG3aClMbSyVilfaOK-EA_qF1zXQL7j3lgP90qLk2isB9DIHennz64ail8UvM0kkkHH6y1waIxveAv0R7_mWVgJ-wJZH273Gr3fHg3mz5Su8E8HFLhAe-MOjb9LWYqn2KKnFGrkLw70j1PVdQ1trvqLwNLwYG1gP7v3o74O7HFGW1zeEFTmKOtmRbDlezKZBnDujZI8FJFuSbPkZJYqaW76tkWSro5Gi0yLgR2BBsnVPdOivLN4p07lIZ_OwfOMfWgTCloQtgEzOjmhZDt_iOYnwsXQObcSpgC1spBwn2eojb1A-7szmznOvxEZw50m2OrAPO8bxgI-ELeL2sxWZrWCY-tN8KMnWyl0ofcsr_JPXShI2j0OPEDqg49XFenm9BtdtG-WBw7arwGJrrA-QvPO-dUF3VhBWVMrvum0iTDMY9i_2DYZ0ros-FePGIwr4HQ4hY8vFrbfRMVfQWmytEegcSnCmsz05rOTOGaG4Rwm20-CEVa0fRL72XNyC7Jo2SBZJaULSxZU1leUNcFt1DWrvBv_9PrTS0RyoECOg3qq2RtjPp5vpmHb6Vpt7TWuluz2tdAcUG-Vpf3Wo0h5tyQUClcoFF6SlRQQqauSWcufpFktjkQa1UUugDVeahhtIdYipTzcPaGOxNiLGvLAB1tAG9GuVoDXeYQ2sf1GOtgqBNqXlDdLWRDFIlkf8LBvudxSt1QZoWbZUGB0O3JMsNxpoqQ2N8V7pioa5QBthtPO2E95YymvFHTqgZafvlZY0RHB0JMsZUM9thZ6KtgsnRKdjoL7TGAkVarRB4D5EKF0aeqt0gP4j_kDlPbclvUPrlNEkyyfDigptYKbCXcsruQVaDsHmKRegAQmz_F1iVwxCd2h5hf-_LSz2bh24_o0r1mr7jByOpEUtUYuH6C3vEbfeJ4a6B0d3yCXaIKODx7sQfbqn5PC2DAW-k6L8SFz7pRwlXiDNa6rcg_PYhI07Z3vDTMcB-URYMKBCK54AIZhrnIySUQiMycvHUWDrs5_Dgn9p29f5_XvCBGS851a-LsEb78sbjWkEr_8hu7--5OXOuA8_xLEEb5rUi3mY-s3c-bXcW2JrUYTYSptQ1AEt0Vpjaa1CDjBaAC0r3YkjkB4nLHhsCB6qaWslDkEwRAp3q1pqpKVih-KWKk2rpgz4ut9T3AtsA7CGic9eXikBSi6ldaoCmm82f6xWmw_LP9eb_Mvyc8E2q-J8s7y-7MHhF8suuofBF989eR6FVOSfQa6jgeCrfQAOt0ZLbLiWhBXe3KLeKI-We2NjKj3KQibNGAvpkeisRe2h5dahhTgdCJuR7Cw8o0bst9coDY-gTlBD6QpCchVlC7o8cRwUyn57hUZvUygWJSWv64CiB_XGv7167GfUi29PjAdlJ7-7suyFc_a5cABxrcxQgzgHWyMf3qx-fHu-2-FICMtSSPdpmqaz2VSOccrGs-kMYsXWl8EPrv9xZZX2sZ666Yuy-dMky-83xnmLvCFsGgozpX0sUUMl-fdVVYyBfZSu1fbi4s_LxJkkTCLsLN1nGCUK9ehTw2HIDbIlxGgUfnQ6FB-hEMU9is4jCNMM-sNya2yoDwmbC2MxFoQov8sz0qG0RvtQkQ0MH_uKsovbOVVpXgfWnUOgd5GGCErfDSXa831gCJXQn0NY-Lx05p1NuBW7mA0kxlbf7JwklfIw2S4Wi8lCSD6bLKblbDzJslk2ns4mQorxbDHlbDrJxPggxU2szIJ-3ypdh3k7i1xCrC-jTxqn9v3QuXae1zXKXNnvV86vnbE2HsP_p5gOjasir8Exf-HvqJc79CyWNzfL1Qe4-bCG4tPFxacv5x__gOL8Yn0NN58i-ey_f8Dn9dWnzzeHTsHVaz2HuQt-_c2-w2GCRYglOkrg_sDy7afACt-0jzkDRbmYZy_6bj_PyO1-zirvZZvnHfbhOTl7oWzi955M8hd35Fl7qXNoKfeei13fy2FFOWR4o8liNk-z0WsHGXk_Xoq_bu5277Q1e3n0zzc-ep7I00wusgU_wdPRbLTIxtP5ZH6yO824HKccFyVf8OmUz1PO5iybcVGO5lmZZSfqlKVsnE7ZhKUsncyTdJrJ8XyapuMsXYxnSMYpNlzVSQDtAConsf12uphOF9lJzbdYu_gViDGN9xAHCWNkkp_Y09i423aVI-O0Vs67Jy5e-RpPV_03HuV34VYMTc4Ak53F_vNN3zYJIU385bPRSWfr059vHvYK3J2y_wUAAP__OeueOA">