clang-format segfaults with a stack dump

[TracerDS]

I have a script that automates clang-format. For one file it crashes with this stack dump:

Stack dump:
0.      Program arguments: clang-format -i Source/panel.cpp
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.22.0      0x00007f98297cee56 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 54
1  libLLVM.so.22.0      0x00007f98297cc6b3 llvm::sys::RunSignalHandlers() + 131
2  libLLVM.so.22.0      0x00007f98297cfbb4
3  libc.so.6            0x00007f98286d0d20
4  libclang-cpp.so.22.0 0x00007f9833fc9170
5  libclang-cpp.so.22.0 0x00007f9833fc8c23 clang::format::WhitespaceManager::alignArrayInitializersLeftJustified(clang::format::WhitespaceManager::CellDescriptions&&) + 387
6  libclang-cpp.so.22.0 0x00007f9833fc7502 clang::format::WhitespaceManager::alignArrayInitializers(unsigned int, unsigned int) + 110
7  libclang-cpp.so.22.0 0x00007f9833fc3dc6 clang::format::WhitespaceManager::generateReplacements() + 486
8  libclang-cpp.so.22.0 0x00007f9833f62448
9  libclang-cpp.so.22.0 0x00007f9833f94c89 clang::format::TokenAnalyzer::process(bool) + 1209
10 libclang-cpp.so.22.0 0x00007f9833f74780
11 libclang-cpp.so.22.0 0x00007f9833f5b687 clang::format::internal::reformat(clang::format::FormatStyle const&, llvm::StringRef, llvm::ArrayRef<clang::tooling::Range>, unsigned int, unsigned int, unsigned int, llvm::StringRef, clang::format::FormattingAttemptStatus*) + 4231
12 libclang-cpp.so.22.0 0x00007f9833f5c501 clang::format::reformat(clang::format::FormatStyle const&, llvm::StringRef, llvm::ArrayRef<clang::tooling::Range>, llvm::StringRef, clang::format::FormattingAttemptStatus*) + 81
13 clang-format         0x0000558673a1fbf9
14 clang-format         0x0000558673a1d52f
15 libc.so.6            0x00007f98286bad68
16 libc.so.6            0x00007f98286bae25 __libc_start_main + 133
17 clang-format         0x0000558673a1a361
Segmentation fault

The file is huge (6k+ lines).
Im using clang-format in a WSL shell.

[llvmbot]

@llvm/issue-subscribers-clang-format

Author: Tracer (TracerDS)

I have a script that automates `clang-format`. For one file it crashes with this stack dump: ``` Stack dump: 0. Program arguments: clang-format -i Source/panel.cpp 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.22.0 0x00007f98297cee56 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 54 1 libLLVM.so.22.0 0x00007f98297cc6b3 llvm::sys::RunSignalHandlers() + 131 2 libLLVM.so.22.0 0x00007f98297cfbb4 3 libc.so.6 0x00007f98286d0d20 4 libclang-cpp.so.22.0 0x00007f9833fc9170 5 libclang-cpp.so.22.0 0x00007f9833fc8c23 clang::format::WhitespaceManager::alignArrayInitializersLeftJustified(clang::format::WhitespaceManager::CellDescriptions&&) + 387 6 libclang-cpp.so.22.0 0x00007f9833fc7502 clang::format::WhitespaceManager::alignArrayInitializers(unsigned int, unsigned int) + 110 7 libclang-cpp.so.22.0 0x00007f9833fc3dc6 clang::format::WhitespaceManager::generateReplacements() + 486 8 libclang-cpp.so.22.0 0x00007f9833f62448 9 libclang-cpp.so.22.0 0x00007f9833f94c89 clang::format::TokenAnalyzer::process(bool) + 1209 10 libclang-cpp.so.22.0 0x00007f9833f74780 11 libclang-cpp.so.22.0 0x00007f9833f5b687 clang::format::internal::reformat(clang::format::FormatStyle const&, llvm::StringRef, llvm::ArrayRef<clang::tooling::Range>, unsigned int, unsigned int, unsigned int, llvm::StringRef, clang::format::FormattingAttemptStatus*) + 4231 12 libclang-cpp.so.22.0 0x00007f9833f5c501 clang::format::reformat(clang::format::FormatStyle const&, llvm::StringRef, llvm::ArrayRef<clang::tooling::Range>, llvm::StringRef, clang::format::FormattingAttemptStatus*) + 81 13 clang-format 0x0000558673a1fbf9 14 clang-format 0x0000558673a1d52f 15 libc.so.6 0x00007f98286bad68 16 libc.so.6 0x00007f98286bae25 __libc_start_main + 133 17 clang-format 0x0000558673a1a361 Segmentation fault ``` The file is huge (6k+ lines). Im using `clang-format` in a WSL shell.

[EugeneZelenko]

Could you please provide reproducer?

[TracerDS]

Could you please provide reproducer?

Here you go: the file it crashes in

[Arghnews]

It would be helpful if you could provide as many details as possible about how to repro the problem
What version of clang-format were you using?
FWIW, I built clang-format at HEAD and ran it on your file and it didn't crash

@TracerDS

[owenca]

Repro: clang-format -style='{AlignArrayOfStructures: Left}' panel.cpp
Version: 21.1.0 and main (5109361)

[TracerDS]

It would be helpful if you could provide as many details as possible about how to repro the problem What version of clang-format were you using? FWIW, I built clang-format at HEAD and ran it on your file and it didn't crash

@TracerDS

Sorry, my bad.

clang-format version:
Debian clang-format version 22.0.0 (++20250812112232+7317e3c9ddd6-1~exp1~20250812232419.1633)

I use clang-format in this way:
clang-format -i $fileHere

Full clang-format config:

BasedOnStyle: Google

AlignArrayOfStructures: Left
AllowShortBlocksOnASingleLine: Always
AllowShortCaseLabelsOnASingleLine: true
#AllowShortCompoundRequirementOnASingleLine: true
AllowShortFunctionsOnASingleLine: InlineOnly
AllowShortIfStatementsOnASingleLine: true
AllowShortLoopsOnASingleLine: true

BreakBeforeBraces: Attach

ColumnLimit: 0
Cpp11BracedListStyle: true

FixNamespaceComments: false
# Disallow goto usage
ForEachMacros: ["goto"]

IndentWidth: 4
IndentCaseLabels: false

KeepEmptyLinesAtTheStartOfBlocks: false

PointerAlignment: Left
SortIncludes: false
SpaceAfterCStyleCast: true
SpaceBeforeParens: ControlStatements
SpacesBeforeTrailingComments: 1

UseTab: Never

[owenca]

The file is huge (6k+ lines).

I've cut it down to the following:

PANEL_Ic PANEL_ic[PANEL_IC_NUMBER] =
    {
        {PIC(0),   PIC(0),   PIC(99),  PIC(81),  0}, // Backbox
        {PIC(1),   PIC(83),  PIC(191), PIC(137), 0}, // AK47

#define PICALL1(a, b, c, d) \
    { PIC(a), PIC(b), PIC(c), PIC(d), 1 }

        PICALL1(1, 1, 75, 50),
};

And with a Debug build, clang-format gives the assertion failure below:

Assertion failed: (PrevIter->Index < Changes.size()), function getNetWidth, file WhitespaceManager.h, line 294.