| Issue |
202764
|
| Summary |
Crash in ASTContext::getTypeInfoImpl with uninitialised C23 auto variable and GNU asm register label
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
danieljwait
|
### Summary
Declaring an uninitialised variable with C23's `auto` and GNU's `asm` extension and register label results in a frontend crash when using the `gnu23` language standard. On an assertions-enabled build an assertion failure is seen before the crash.
This crash is present from Clang 18.1.0 to trunk. Clang with `-std=c23` instead of `-std=gnu23`, and GCC, both gracefully rejects this input.
Input generated by fuzzer.
### Revision
```
clang version 23.0.0git (https://github.com/llvm/llvm-project.git dd87edd1f48b02e4a58dbd0a6fdda07c36c4dea8)
Target: x86_64-unknown-linux-gnu
Build config: +assertions
```
### Reduced testcase
```c
auto register i asm("esp");
```
### Reproduction command
```bash
clang -std=gnu23 -fsyntax-only
```
### Observed behaviour
Clang aborts with the following assertion failure:
```
Assertion `!A->getDeducedType().isNull() && "cannot request the size of an undeduced or dependent auto type"' failed.
```
Triggered at:
```
clang/lib/AST/ASTContext.cpp:2542
```
Relevant stack frames:
```
clang::ASTContext::getTypeInfoImpl
clang::ASTContext::getTypeInfo
clang::Sema::CheckAsmLabel
clang::Sema::ActOnVariableDeclarator
```
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