<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/116175>116175</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Crash in clangd 19.1.3 during background indexing
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          martin5233
      </td>
    </tr>
</table>

<pre>
    During indexing clangd crashes with the following stack trace:

```
 #0 0x00005629fd65cfab llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/usr/local/bin/clangd+0x763fab)
 #1 0x00005629fd65a92b SignalHandler(int) Signals.cpp:0:0
 #2 0x00007fada49ef050 (/lib/x86_64-linux-gnu/libc.so.6+0x3c050)
 #3 0x00007fada4a3de3c __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
 #4 0x00007fada49eefb2 raise ./signal/../sysdeps/posix/raise.c:27:6
 #5 0x00007fada49d9472 abort ./stdlib/abort.c:81:7
 #6 0x00007fada4a32430 __libc_message ./libio/../sysdeps/posix/libc_fatal.c:156:1
 #7 0x00007fada4a477ba ./malloc/malloc.c:5664:3
 #8 0x00007fada4a4aa9c _int_malloc ./malloc/malloc.c:4006:13
 #9 0x00007fada4a4b372 _int_realloc ./malloc/malloc.c:4874:20
#10 0x00007fada4a4c21f __libc_realloc ./malloc/malloc.c:3491:3
#11 0x00005629fd61a614 llvm::SmallVectorBase<unsigned int>::grow_pod(void*, unsigned long, unsigned long) (/usr/local/bin/clangd+0x721614)
#12 0x00005629feb73ae2 llvm::BumpPtrAllocatorImpl<llvm::MallocAllocator, 4096ul, 4096ul, 128ul>::AllocateSlow(unsigned long, unsigned long, llvm::Align) (.isra.0) TUScheduler.cpp:0:0
#13 0x00005629feb7e9fb void* llvm::StringMapEntryBase::allocateWithKey<llvm::BumpPtrAllocatorImpl<llvm::MallocAllocator, 4096ul, 4096ul, 128ul>>(unsigned long, unsigned long, llvm::StringRef, llvm::BumpPtrAllocatorImpl<llvm::MallocAllocator, 4096ul, 4096ul, 128ul>&) (/usr/local/bin/clangd+0x1c859fb)
#14 0x00005629feb81d78 clang::clangd::(anonymous namespace)::PreambleThread::build(clang::clangd::(anonymous namespace)::PreambleThread::Request) TUScheduler.cpp:0:0
#15 0x00005629feb8278a clang::clangd::(anonymous namespace)::PreambleThread::run() TUScheduler.cpp:0:0
#16 0x00005629fed43815 void* llvm::thread::ThreadProxy<std::tuple<clang::clangd::AsyncTaskRunner::runAsync(llvm::Twine const&, llvm::unique_function<void ()>)::'lambda0'()>>(void*) Threading.cpp:0:0
#17 0x00007fada4a3c144 start_thread ./nptl/pthread_create.c:442:8
#18 0x00007fada4abc7dc clone3 ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:83:0
Signalled while building preamble
  Filename: removed
  Directory: removed
  Command Line: /usr/local/bin/clang++ --driver-mode=g++ -DBOOST_ATOMIC_DYN_LINK -DBOOST_ATOMIC_NO_LIB -DBOOST_FILESYSTEM_DYN_LINK -DBOOST_FILESYSTEM_NO_LIB -DBOOST_NOWIDE_DYN_LINK -DBOOST_NOWIDE_NO_LIB -DBOOST_PROGRAM_OPTIONS_DYN_LINK -DBOOST_PROGRAM_OPTIONS_NO_LIB -DBOOST_REGEX_DYN_LINK -DBOOST_REGEX_NO_LIB -DBOOST_SERIALIZATION_DYN_LINK -DBOOST_SERIALIZATION_NO_LIB -DBOOST_SYSTEM_DYN_LINK -DBOOST_SYSTEM_NO_LIB -DBOOST_THREAD_DYN_LINK -DBOOST_THREAD_NO_LIB -DHACK_PROTECTION_AVAILABLE -DLINUX -DLINUX64 -DPowerBy3dx_EXPORTS -DQT_CORE_LIB -DQT_NETWORK_LIB -DQT_NO_CAST_FROM_ASCII -DQT_NO_DEBUG -DQT_NO_KEYWORDS -DUNIX  "include paths removed" -m64 -D_GLIBCXX_USE_CXX11_ABI=1 -fPIC -pipe -Wall -Wsign-compare -Wunused -Wfloat-conversion -Wno-unused-local-typedefs -fvisibility=hidden -Wno-missing-braces -Wno-deprecated-builtins -Wno-float-conversion -Wno-format-security -Wno-register -Wno-unused-variable -Wno-unused-but-set-variable -Wno-unknown-pragmas -Wno-shift-negative-value -Wno-unused-private-field -Wno-int-to-void-pointer-cast -Wno-unqualified-std-cast-call -Wno-constant-logical-operand -Wno-self-assign -Wno-unknown-warning-option -Wno-c++11-narrowing -Wno-deprecated-declarations -Wno-ambiguous-reversed-operator -Wno-unused-function -Wno-unused-lambda-capture -Wno-reorder-ctor -Wno-array-parameter -Wno-inconsistent-missing-override -Wno-overloaded-virtual -Wno-pessimizing-move -Wno-sign-compare -Wno-inaccessible-base -D__CATERROR_DIRECT_BASE_OF_DISABLE_CHECK -fgnuc-version=11.2.1 -std=c++20 -fPIC -pthread -o removed -c -resource-dir=/usr/local/lib/clang/19 -- removed
  Version: 0
```

The arguments to start clangd were:
```
I[08:31:18.306] argv[0]: /usr/local/bin/clangd
I[08:31:18.306] argv[1]: --background-index
I[08:31:18.306] argv[2]: --background-index-priority=low
I[08:31:18.306] argv[3]: --log=info
I[08:31:18.306] argv[4]: -j=8
I[08:31:18.306] argv[5]: --clang-tidy
```

Running the same file with --check by hand succeeds with a couple of messages like this:
```
E[08:47:50.462] tweak: ExtractFunction ==> FAIL: Cannot extract break/continue without corresponding loop/switch statement.
```
which from my understanding do not indicate a real problem.

Unfortunately I cannot provide the source file triggering this issue. I hope this information helps nevertheless.
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJysWFtz4rgS_jXOi0qULWMuD3kgXGaoyYQsMJvseXHJUhu0kSWvJEM4v_6UbAOBZHZyqqZqhkBL_enrVl8kUWvFRgHcBsldkExuaOW22twW1DihEhLHN5nmh9tJZYTaIKE4vPovTFK14YgZardg0V64LXJbQLmWUu_9DOsoe0HOUAZBPArCSRAeP3th-6_-iQIShyh8DcMwTHpkmPNewnKaISl3hVeNR_Zgmy-PRii38sjrGpgMzpMM3afaOgO0CEgvIGMklAvIEAVkEJBZZU1AZlIzKgMyy4QKyKyxIiB34Wu_F-c0C8jwTCq6IkWHJEMrsVFUfqWKSzABGbRrNGLbYWUZxKOw_n8CIi1QP6ecdoeQh0nYspIiC8jsddBLe10shape8UZVzQDrWN3p1exiFibhBbn4ApPGHGKG0rR0WwOUpy9CylQUpYQClKNOaIU6AZmp0nnz307rsCAedbtBPOr3zvjdK86QZwQZKizUOLa2NyCzTv3rYDmU1gNrK14DMqtn1sikH8SjN8DJJTAfdvsE0Uwb1wA73vikFtUIg8hzOyP0rkwn3ThEaeo9lhZgLd00HKXIhP45xXp-Th1tPBAlPf95XqZ_uUy3389ojVtQKTU7fam1k17PezA-qw-u1CkdMpQK5dJG7adQ3TCsmbzBGl5hZXGfNFgGfgE26HtepI1GH9XhFRgjUX5036_g4u4wOpvp0a6SJKK9qPsmc1de-U9gTps7aiGIx5WqCw6vszOeNtM2Ru_TUvOADHZa8ICMfP6epkqtNh8IPpvaJOpF3VP2eNbkLWvI-jEF8ob1XVWUj86MvN3UaTMvShnE4_OE77VLTuOeWzcc9ip5-S0ig0qejGynw0rqfUAGv7Ju_IbQSIqNag3uCGtox1cDtP6xYlvglQTzvvJ4O-MrO2GYZ6j18Ntdcr66f6flVDlzaDbKy2nL-Em47Tc4XLjg9_to-n86pWG9hPxS_NuJ-WbyyVCL2CAZ5tlFrHUv92AQ8f6g6Z8NnVa9_h6QAVVaHQpdWaRoAbas29zw2P6AFpmEdV29G1lWCenz5vchLuGfCqz7VIAlV8aR_oD-RuNMpWq_f4JJ74IJ78aDKPkg1N0b9GalR6NffWhb14pdVUpfqX5ixsgeFFtT-7KslAJzIlrLL04k671QgJhW3pm9yyitlPingjSvFPPNOYjHnmsTZcM66oZHr_UlLTJOw4D0z8N1tpxq5RA1tgi1-dg7V80sZlG3649oxqWNRz46HTAD1EF7PiC-E58Br9pbxvqcISa1grjpHsKy9723UnXrtQe7qzuwql5Px586k7x-Z-WXis8GNIcrCRztt0ICqkPenzHLNmTaTolmQoIPrCAeIQOF3gE_Dk2EqbvQ4YOxsS4Kqji6F6pW_bc8D8hdQO4QxtyIHRhcaA5BPDnJJ3eLxWqdjtaL7_NxOvnrIb2fP3y7lj8s0vv5efZsfj9d_bVaT7-_13gzdqX1sHiaT6bvNVr51ezH5eLLcvQ9XTyu54uH1Xu16wlX-svpl-nze61GfDV3NV3OR_fz_4w80nudy-Fr3Z_44WMfrL8up6PJ-9mt_DT762j8zVu4no7rRUd_jub3o7v7KcKT-_nDj-fj314X4cmj3oO5O8T8NZ0-Py6W6xXCkz_W6XixnLaAf6zTh-n6abH89kawSMcjv2XLxfd0tBrP5yf5ZHr348vp17fpX0-L5cSj_niYPyMUECIUkxUHVFK3tacIJQThouaUfrmf342fn9Mfq2k6fn6OonR0Nw_iSYRw_jgfI1yKEhB-olIi_OS7Jma6KKnxwkpVFjjCT7nU1GGm1Q6M9bcC_KQ0boZxHe_YHUrgkFuE852wIhNSuEMQT7aCc2gVCmGtUBuc-WuYbWQcSgP-uMCxz1AnVDvw8Zq5NgV12AKrjHCHRmhgI6wDc0FrR42gmYQLYVZ5Xfdu8EXpvcKloZuCtuvbrcgdVrChTuwA76isLrFKI3bUAc4FSN6MCOWw09hXWFxqoRwYzKh1R71_KipFLoBj63g9glnjeaVxXfKpcljqjfAu1SUYX2EaOiBz3Ny7L0nvqVHeqbp0Jy-xprBEEVbUmOZqfe1tDkxSU1_yWotpkYlNpSuLDXinA28oOH3p2WP7uYyCut1gRktXGTjuizbcu-CEQI2hB1xSQws4bZhQ3nS_g8qdYkTvwBjBWyT_S2rK_b4K4yra-qwEa0Uh_us1fOy3vroM43oJypifm0nAGbXgcyMdj9bT5XKxTCfz5XS8Tu9Gq2m6mKWT-cpneTr-Oh1_QzjfqIrhNgx97kQd0okQrnv_pPU1CU8Z1fZGrI8JiTBD2IDVlWGAuTBBPHnXLpoLbNsuZtEQYXzdcv48Uhih8MNXkeZzvQVEzabyl3iLnG5a9vH1ZQ_mzdvKpf48SO7Cgb-r-QtbNOjEYS9IJh5t54eCZPKrVsc_hRS1SBhnlL1sjK4Ux_U70afUyU_VfVZq05Qef2P6DFp8QpN6E8QToXL9KcXuUfHvIJ4MPqWSnNaqvYWd4Id_2Up_WvTJ67aALC0A5f4oUz-cYcy2wF5QdkBbXyVsxRgAb5_VKGLan0iRzlH7vGGRFC-A3FbYn-3_9Ei-2w_iURJ2uj3vauT2QF887emrM5S52bEC-ED2_6ZoNprf-xljqpR2CJqJKDNek8yYVk6oquGuK4eYNgZsqVV9JpNal_6ItxeObX28uvoJqvMhy_1WsC3KjS5QcUCV4mB84ayBuEZ-eaG48GUOUWSASlQanUkoOm99-0Pl2rhKUQfygOaINcxLo3e-7tQurzO2cbozYrMB0-yGsEhYW0EHzdFWl9CKVNOevGe2IEuLlC-kbgsSrO3c8NuYD-MhvYHbqB9HST_sRcnN9rabRN0h9GmPxTynUdIfDIDzYRT1Ic-Tfn4jbklIulEUdcN-EkZJh_IB9OIoDvsJHyYsCbohFFTIjr8rdLTZ3NT0bqOoF_WTG0kzkLZ-rSVEwb4hHxC_uTfm1ivhrNrYoBtKYZ09wzjhJNyODbVbJNSxhkTDTtSJEW_ed885eHrqvamMvN06V9ahRmYBmW2E21ZZh-nCFw5_pWn-4NLov4G5gMxqVv7E39Le3ZL_BQAA__9iK-lf">