<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/63102>63102</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
clang-17 crashes at llvm::isPotentiallyReachable
</td>
</tr>
<tr>
<th>Labels</th>
<td>
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
wierton
</td>
</tr>
</table>
<pre>
I've encountered a crash that cannot be reproduced on gcc.godbolt.org, but it consistently occurs on my local machine. I'd like to provide more information on the compilation steps that I used with clang-17.
Before that, let me share the bug-triggering test case:
```
#include <stdlib.h>
int d;
int e;
float **f;
int main() {
const int N = 32;
float **g;
float *h;
int i;
g = (float **)malloc(N * sizeof(float *));
f = (float **)malloc(N * sizeof(float *));
h = (float *)malloc(N * sizeof(float));
i = 0;
for (i; i < N; i++) {
g[i] = (float *)(0);
f[i] = (float *)malloc(N >> sizeof(float));
}
for (i = 0; i < N; i++) {
for (e = 0; e < N; e++) {
g[i][e] = 2.0f;
f[i][e] = 1.5f;
}
h[i] = 0.0f;
}
{
float **a = g;
float **b = f;
float *c = h;
int n = N;
int l = N;
float p;
float o;
int i, j, k;
float s;
for (i = 0; i < l; i++)
for (j = 0; j < n; j++)
for (k = 0; k < d; k++) {
p = a[i][k] * b[k][j];
c[i] += o;
}
}
for (i = 0; i < N; i++)
if (h[i] != 3072.0f)
abort();
for (i = 0; i < N; i++)
h[i] = 0.0f;
for (i = 0; i < N; i++) {
h[i] != 0.0f;
abort();
}
return 0;
}
```
When compile it using my `clang-17` with option `-O3`, it outputs:
```
$ clang-17 -O3 small.c
small.c:50:10: warning: inequality comparison result unused [-Wunused-comparison]
50 | h[i] != 0.0f;
| ~~~~~^~~~~~~
small.c:50:10: note: use '|=' to turn this inequality comparison into an or-assignment
50 | h[i] != 0.0f;
| ^~
| |=
small.c:15:8: warning: expression result unused [-Wunused-value]
15 | for (i; i < N; i++) {
| ^
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: /home/xfou/disk/llvm-project-trunk.obj.release+assertion/bin/clang-17 -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -dumpdir a- -disable-free -clear-ast-before-backend -main-file-name small.c -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/home/xfou/bugs/21 -resource-dir /home/xfou/disk/llvm-project-trunk.obj.release+assertion/lib/clang/17 -internal-isystem /home/xfou/disk/llvm-project-trunk.obj.release+assertion/lib/clang/17/include -internal-isystem /usr/local/include -internal-isystem /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O3 -fdebug-compilation-dir=/home/xfou/bugs/21 -ferror-limit 19 -fgnuc-version=4.2.1 -fcolor-diagnostics -vectorize-loops -vectorize-slp -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/small-4a0367.o -x c small.c
1. <eof> parser at end of file
2. Optimizer
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 libLLVMSupport.so.17git 0x00007f0d0a9350df llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 63
1 libLLVMSupport.so.17git 0x00007f0d0a9326ce
2 libc.so.6 0x00007f0d0a35f520
3 libLLVMAnalysis.so.17git 0x00007f0d0b986d53 llvm::isPotentiallyReachable(llvm::Instruction const*, llvm::Instruction const*, llvm::SmallPtrSetImpl<llvm::BasicBlock*> const*, llvm::DominatorTree const*, llvm::LoopInfo const*) + 51
4 libLLVMAnalysis.so.17git 0x00007f0d0b950fc3 llvm::EarliestEscapeInfo::isNotCapturedBeforeOrAt(llvm::Value const*, llvm::Instruction const*) + 275
5 libLLVMAnalysis.so.17git 0x00007f0d0b94b187 llvm::BasicAAResult::getModRefInfo(llvm::CallBase const*, llvm::MemoryLocation const&, llvm::AAQueryInfo&) + 247
6 libLLVMAnalysis.so.17git 0x00007f0d0b925fdb llvm::AAResults::getModRefInfo(llvm::CallBase const*, llvm::MemoryLocation const&, llvm::AAQueryInfo&) + 107
7 libLLVMAnalysis.so.17git 0x00007f0d0b927ac9 llvm::AAResults::getModRefInfo(llvm::Instruction const*, std::optional<llvm::MemoryLocation> const&, llvm::AAQueryInfo&) + 409
8 libLLVMScalarOpts.so.17git 0x00007f0d0c54f6c0
9 libLLVMScalarOpts.so.17git 0x00007f0d0c550bdd
10 libLLVMScalarOpts.so.17git 0x00007f0d0c556b9d
11 libLLVMScalarOpts.so.17git 0x00007f0d0c558acf llvm::DSEPass::run(llvm::Function&, llvm::AnalysisManager<llvm::Function>&) + 511
12 libLLVMPasses.so.17git 0x00007f0d098142e6
13 libLLVMAMDGPUCodeGen.so.17git 0x00007f0d13151a55
14 libLLVMAnalysis.so.17git 0x00007f0d0b9a802b llvm::CGSCCToFunctionPassAdaptor::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) + 1835
15 libLLVMAMDGPUCodeGen.so.17git 0x00007f0d13136576
16 libLLVMAnalysis.so.17git 0x00007f0d0b99fa4c llvm::PassManager<llvm::LazyCallGraph::SCC, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&>::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) + 364
17 libLLVMipo.so.17git 0x00007f0d0d625bc6
18 libLLVMAnalysis.so.17git 0x00007f0d0b9a3e3e llvm::DevirtSCCRepeatedPass::run(llvm::LazyCallGraph::SCC&, llvm::AnalysisManager<llvm::LazyCallGraph::SCC, llvm::LazyCallGraph&>&, llvm::LazyCallGraph&, llvm::CGSCCUpdateResult&) + 494
19 libLLVMipo.so.17git 0x00007f0d0d625b76
20 libLLVMAnalysis.so.17git 0x00007f0d0b9a1a02 llvm::ModuleToPostOrderCGSCCPassAdaptor::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) + 3010
21 libLLVMipo.so.17git 0x00007f0d0d62ca6f llvm::ModuleInlinerWrapperPass::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) + 1327
22 libLLVMPasses.so.17git 0x00007f0d098112a6
23 libLLVMCore.so.17git 0x00007f0d0b3e9376 llvm::PassManager<llvm::Module, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) + 1222
24 libclangCodeGen.so.17git 0x00007f0d0e424ecd
25 libclangCodeGen.so.17git 0x00007f0d0e428438 clang::EmitBackendOutput(clang::DiagnosticsEngine&, clang::HeaderSearchOptions const&, clang::CodeGenOptions const&, clang::TargetOptions const&, clang::LangOptions const&, llvm::StringRef, llvm::Module*, clang::BackendAction, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>, std::unique_ptr<llvm::raw_pwrite_stream, std::default_delete<llvm::raw_pwrite_stream>>) + 3432
26 libclangCodeGen.so.17git 0x00007f0d0e8a74e5
27 libclangParse.so.17git 0x00007f0d07c87ba9 clang::ParseAST(clang::Sema&, bool, bool) + 1145
28 libclangFrontend.so.17git 0x00007f0d0d0bb249 clang::FrontendAction::Execute() + 201
29 libclangFrontend.so.17git 0x00007f0d0d031806 clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) + 342
30 libclangFrontendTool.so.17git 0x00007f0d0fab608c clang::ExecuteCompilerInvocation(clang::CompilerInstance*) + 460
31 clang-17 0x000055fddf9545c5 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) + 2549
32 clang-17 0x000055fddf950293
33 clang-17 0x000055fddf95193e clang_main(int, char**, llvm::ToolContext const&) + 5374
34 clang-17 0x000055fddf94a9e3 main + 51
35 libc.so.6 0x00007f0d0a346d90
36 libc.so.6 0x00007f0d0a346e40 __libc_start_main + 128
37 clang-17 0x000055fddf94aa25 _start + 37
clang-17: error: unable to execute command: Segmentation fault
clang-17: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 17.0.0 (wierton@114.212.81.121:~/llvm-project-trunk ff75a2be34fd76350216c36b7ea4c3f338df6215)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
clang-17: note: diagnostic msg:
********************
PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang-17: note: diagnostic msg: /tmp/small-4366b3.c
clang-17: note: diagnostic msg: /tmp/small-4366b3.sh
clang-17: note: diagnostic msg:
********************
```
The preprocessed source and associated run script mentioned in clang-17's diagnostic message:
[attachments.zip](https://github.com/llvm/llvm-project/files/11644808/attachments.zip)
Here are the configuration and compilation steps I used for my `clang-17`:
```
$ cmake ~/llvm-project-trunk/llvm -DLLVM_TOOL_CLANG_BUILD=ON -DLLVM_ENABLE_PROJECTS=clang -DBUILD_SHARED_LIBS=ON -DCMAKE_BUILD_TYPE="Release" -DLLVM_BUILD_LLVM_DYLIB=ON -DCMAKE_C_FLAGS=-O2 -DLLVM_ENABLE_ASSERTIONS=ON
$ make clang
```
My clang's version (with commit hash):
```
clang-17 --version
clang version 17.0.0 (git@github.com:llvm/llvm-project ff75a2be34fd76350216c36b7ea4c3f338df6215)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzcOl1zo7iyv4Z5UeECCbD9kAd_zuTeTJIbZ3dq74tLQIM1AYkjiUwyD_vbb0mADY6dGe_OqXtqUy4Hi-5Wf6ulFlWK5RzgygnnTrj8QGu9E_LqGwOpBf8Qi_T16trB42dAwBNRcw0SUkRRIqnaIb2jGiWUc6FRDEhCJUVaJ5AiwVGeJKNcpLEo9EjI3MELFNcaMY0SwRVTGrguXpFIkloqg1C-okIktEAlTXaMwwiZqVNUsCdAWqBKimeWAiqFBMR4JmRJNRPc4OodoESUFSuaIaWhUg1_16hWkKJvTO9QUlCeu_545HhLx5s133PIDEUDbJgsQKMSkNpROwgornNXS5bnIBnPkQZlhFbgkJaAE3ntp_mJCeNJUaeAHLJQOi1YPNo5ZNW8Zlyj1CHzwy_Y_8oKQTVy8MzBs2wAU1LGHTxx8BQ543YcWU1qZN7fIocsEcF7JIT6xPJT47veoKHBer9zS8_Bkz4VB09LWhQicfDk1owhxb6DyIZgU_PpTffLKO1OUHqfzBsSzJLw9iN7JoU0hI0GLMwC3dpHB8_tp6_13AnnzAmXp7hx8MQbzohQ9g58n3uycsjqBwI44-Uxy3uJfsg42iPBAQkOSPCetE44h04IPPKygYgHIftg_igcgvW4R2jXV4s3oNiDG3Lf8yBq8fKhpnvvY_s-O_0-sS97_m_cn9vB2wGGGS-Oxo_pVSfmEEPSzCSWr-br6QSwGo6dsWsxtOtA-Q3K1wPKV4vC7eNJlD3S0wHpySKl9vGM_zR_lcWhB5M_WTviGYrbH044_2r-kTe4yd7seG6oiDcwA-tf6u4902UG_uBl2LcZ0htb7x1qg8ZC6ia99jPXpVO-49J_LVyPufeOA-804z21SdC15P2M1707XrXs95cd8HYhBbNU18oseeUrciKvWzydyGtWU1HZtdaJPPeOGEJ4YXBErataq_PLY7Bfh5F7R5AySXCUNG-7H2QWeg6Z-eYLfaOSM56bR8bhXzUtmH61bFLJlOBIgqoLjWpul3onnLtfmmf3AGTcsdNb6CFnvEA_pWJkQf80f064-rN5OM8rF9pUBqboQA4eO-OFQ5YOHpsKxppC75g6IwbjWiDKkZBuU5mVwPXfYNrwezyGDmFmOTuSxA8dMpscKR1eKglKsXc1_UyLGvpK9sN2wksW1z7vzdD9zWq2WSFVxyXTiJpyzFSaQmqj0p3WlXU1vHbwOmd6V8ejRJQOXhfFc_fPraT4Col28JopVYNy8BpRnqKuULP1o61pY5o8aUkTMN5c2ZI2AWWEVaKWzbDBpEqJhFENKZI1RyqRrNJtXbnRNHlCaV1W-yDwRuheilzSElGZ18awhm3k4PVOlODg9UsmagevU6aejrh2taz500jEX0cSCjClJ55TpUCa-HPwOja14foQVEniI1OyVgWgl0m0jQK35k9cfONuwXj94ua8Ri6UTLsi_opcw2nKJKIuclOmaFyAm0kA5CYFUOOM2o1tlewa9QBPkWsKUjdjBbicmnK58SDklhJMFW84c0uRQoEqliC3YolbwDMUCDc_mHIrBsgtM0lLcCvBzObCIUsuOCA3K6neuSAlF8jNsspNBDdm0Q5ZCo7cjAtXipqnjOeugUVuaathWSfaxE_BqAKF3Kzm3xhPXW2kUg5ZYuRqKnPQblLVRj1uFCBX1xzsQA4cpOE4hbg2Nb95ZeNgmacxcrNEPIOkObi9_YabMmnD_MiYcZ0bV8M-ciU0_mNAf43VCxZ3Vnfw2tjdqpDTwmXqVWko_z3zmCBqw-bkjLWSBsts5X4OtHHf0Wg_V54khuXGc_ceaybHHeDR1wnYtxPDi3lI3jLQgp6g8z725VPYBc_NrG9d6EAZSCmkWzCTBv0pcrOc14n7DNIkZocsgxEe-dZBCyHdlNGcC6VZopD7DCYo2HdwCyGqwYAqKuRmNE2lYjlyl9vtx8Vi-2n2-2q7_DJ7WOPtYn29nW0-O2TpI1cYkXRZOXhtQ94NqEei8Ugg9wUlw7XcH7XpnCzMloasUEWlAomoRiaHiAyZBNIA4xb4rtKsZN9BHqdSW3OIWiP1WsaiQCbtKLuZ4aqWgF5FjXb0GZB17gbI0EGMm3cS3c8ePyEhkQJt8z3wZyaFXWPRM5Wmjrm5-f3zdvPH5_ndzfX_rh62BsWUO1ogm6DMA7Obsn1eRwWLDdqmrsyaNFJi5I9zpttV1nvxPM8bZ17q0SkJvTSz_Bl8MlOvqnm4l4xrK-pjs_RMDkCSftsKpSXQ0sGRrbG4tosmnqOItKq-iA0cJZ3WkUFMDHg0ACJhFuK2YiOooz7jtHhVTB3I93Di6SRKQ9KTj6l7oYFrRovi9QFosjNJeCDddZuyTW1h87fdvS3QJRAb43T3Wm5AX5dV4ZDF4d2cKpbMC5E8GTSyOkNiKUrGqRby0Sx7p2FuhKiueSZ6rxsjhH6jp-C8mo6NEE9DL0v6ulpRWTBQeqUSWoGZp9PhrdALWulaQtocVd3JmR4o8XdTel2kvoZxPA4bzsOftXAQ-5MxOlLvbPZgq8JmKAf9WaQPkFkZ-mwuaFHMqTrH6WcohXy9aYuHDigaAs1m_1ODfG1oR3tBgnEjSHSJCXCYpfGAdiOH-v8TxPdaQcY_axE8psn0rwhxLq6UThuAZntHh_E0lK0XUD8lXuC1u-XJPl8ltKDyrtJDS_VETMIgi5I2FU0vwQu9OE3b_OhdhBjF0w7RvwhxQpN-gl9uVvdUtaaQNR8YYF3zpCmxjnXXWvwz5TQ3NfHiBBJZ9fQa-m0K8nHHrpkXjt1_wO504gcYohaR7P3t8_Lj_W8LkcJH4Keczid-6NOwTR3-RVmPTjzcD7nFx81i8Sg6qQzTs5RWWsjTOruh319N9H2UtNq12X-xuEiD50gMUv0ABkedtt-FGby1gv1WpVRDmxx7QT4hnfLCS7ROonDcmeuiRDfNaJD0mDNq_quq-beo9m_qlaz-wd5CoqC1-bizOavEm8Ae2jyNcBgnnbNMLgpRAgT6OQyemdSbxeIBKqAa0vMZ7R-h72Da6Xt6ob674MTeRfr2qYf71YNI6wIexb1Q-k6mIC2zP8yMDdpFum5RBisJ8fx2qcX-SfGHQic0yt7wfs0LxkF-kbSqQJ53l1_Esk9wWzThs6vfcNnzMe1MtV_2FkLCCSP3TUVgSsbRT-TRTrDLpTqXyX6VqjDGreB22baHOu8sOh4EOICkrYVweB7nWFkQ4ElAJs1Jf7vDKZmeN8eHd7ZF4OBJ7_XycGCx4jnjnbQ9kE9AU5AboDLZ3dnqVA3Kzx5oy-APoB7tQeAPgG4oz0-B9DagWjKeP0B2tA9ojTY7ItgqYdZWf8Pdmpa1Ys_wANmC63s9tOlz1obSmhWwsUdM7fq5r9przv5Vw7Y6wpT027b6JpmGbXeW0ENKIaN1obcpFKDhB4iNm3b5IiCdR0UXeMeEjgNoiyA83iPeU6ngpCOOk8k4ptO-Gi3wbPM4dKMNlLQ1UCxEcfjfRoAfdNNO9tOupeAaeDpkuJ_pvDjGwWD2Dqe1YuPhL5DUGrp7GmZj6rWFOZ6-M9tgJuJPvGjoyrYdJ82GjfIEBnN1TjQ5z1ovuQetrYj3hptHIYqTHGU0jrxJMojkZu4DY8_dfnDAxxvGDycPQdcNJP6hGXjyr-EkDLM0zaZhECYhShJ_296H6aVCKemrCUGySHZUHra0TXwMx_ACPQuW9o9CwqDdmhJ84Gg4uYen7XEbIRdx7U8JNAgd3_YIr-GquxDTTwPGGAtjlxfdSzntXo-M2wKFBGc4DegUiL0yNDifIuG5w74gSqedQaIe0HnR9ogQeGi7NShbpanU2_20Pp60JMdn-aQ4RA1e46DtQr5vNZMZssfetqPKaVzYm2DQ-B9KRFlSbnIY2kBeAtfNiYtNZu9QsoMoaz2_I4MyygpIUVrbSRTLOS2Qgye1AuQ-2zEAxHrePu1NgtqTeOSPR97IM4jtPTon8Hw_GGEfjyb-yMe-Q2Z_nuzCoCwbhxTHQIIsHUck9LAfJSSKx0CDhGSETNIswn64n7pZwYxQ5xp9LdxOAk2R7cgZ6Eoo9tK8suFZFJAumWxbkoe-zBsldv3tQ38BlSo_NPvx3_j0LiK0Xd_Z4-Ns8Qk9flqh9d3Nzd2X69uPaH19s9qgxzs7PP_tI3pY3d89PO55uD_VtZ0oE0BnO7d7AAn2FqJ5S_We5E9p4E1rhERRTLpuyN8hoXaXG-JXmePUNZHHHZzqjZ9XLzLByQSHFDG-zwYOHqsB_6AUzeFYhnBOtabJzjbNR99Z5YRLB08ubv1nrLCdf9-PgmDiTRy8PibchVXz_QkkoO4aaCJ4xvJaNimGNnnj6MJpe9c0E_LtnZl378OU9AnQ6ZzQDiJ3abtTj3d3N9vFzez243b-2_XN0iHLu9vu5ep2Nr9Zbe8f7v5rtXjcOGTZpCZ3aWG3m0-zh9Vye3M933R4i8-z_141pLaPf9yvbBcSP3SdYNyRbiDs4_KPm-v5EH-xXd_MPhqi7h0-4ma22aweHq_vbps5D1JboZt64byrfX5tQYyvdCnW5la9s5mbabSjatdvyh0ROlyM2HdL303bOdNO4PUcisxOONR_aK7ey_4hvSLplEzpB7jyo0k4CcOQTD7srsaxRwnxcBaGIaRxkEXJZBxN43js-16Mkw_sCnuYeJEXeKGP_cloOvZJMqVTnPhhnE5TJ_CgpKwYGX2MhMw_2Fs1VxHxPfyhoDEUqrtSLq-s0mwjO_AKprQ6oGmmC7ja28fewAGFqP5hE_FDLYurv375x3L6fwEAAP__DlPjRw">