| Issue |
153938
|
| Summary |
[MC][ARM] `Clang` Crashes When Assembling Invalid ARM `ldrexd` Instructions with `--triple=armv7-none-eabi`
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
venkyqz
|
## Description
When using the latest **trunk assertions build** of Clang/`llvm-mc` with the `--triple=armv7-none-eabi` option to assemble ARM assembly code containing invalid `ldrexd` instructions `ldrexd h0,r0,[r8]`, the assembler crashes with a **SIGSEGV** due to an assertion failure in `ARMAsmParser::parseInstruction` / `ARMOperand::getReg`.
Expected behavior is to emit diagnostics (e.g., “invalid instruction”, “destination operands must be sequential”), not to crash.
---
## Interesting Facts
- **Clang 18.1.0**:
- Clang **18.1.0** with the same triple/inputs produces correct error messages and exits cleanly (**no crash**).
- This is the latest version that still works, indicating a bug introduced after 18.1.0.
- **ARM gcc 15.1**:
With `arm-linux-gnueabi-gcc -march=armv7-a`, GNU `as` correctly diagnoses the invalid instructions with errors such as:
- ARM register expected -- `ldrexd h0,r0,[r8]'
It does **not crash**.
---
## Steps to reproduce
This issue was reproduced in Compiler Explorer using `x86-64 Clang (trunk with assertions)`，`x86-64 Clang 18.1.0`, and `arm gcc 15.1`
Comprehensive reproduce link: [https://godbolt.org/z/TW6WcqKWj](https://godbolt.org/z/TW6WcqKWj)
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