clang-format 21.1.2 out of memory

LLVM ERROR: out of memory
Allocation failed
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0. Program arguments: clang-format.21.1.2 envdep.h
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 (error) 0x00000000004534b3
1 (error) 0x0000000000450f45
2 (error) 0x0000000000454476
3 (error) 0x0000000000463690
4 (error) 0x00000000004635ff
5 (error) 0x0000000000404342
6 (error) 0x0000000000424c7f
7 (error) 0x00000000004282b9
8 (error) 0x00000000004becea
9 (error) 0x00000000004bda56
10 (error) 0x00000000004d9290
11 (error) 0x00000000004bc917
12 (error) 0x00000000004912e2
13 (error) 0x000000000049165d
14 (error) 0x000000000040b958
15 (error) 0x0000000000409642
16 (error) 0x0000000000644fd9
17 (error) 0x00000000004068de
Aborted

Start by reproducing the clang-format 21.1.2 failure on envdep.h and capture a symbolized backtrace using llvm-symbolizer as suggested in the report. Compare the behavior with a suitable clang-format version or configuration, then narrow the failure to a reproducible input and verify that formatting it no longer aborts with an out-of-memory error.

Written by the indexing model from the issue text.