String literal concatenations which mix different encoding prefixes are incorrectly accepted in ignored attributes
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accepts-invalid
clang:frontend
confirmed
- Dominant language
- LLVM
- Stars
- 40.5k
- Forks
- 18.7k
- PR merge metrics
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Description
The following program demonstrates the issue:
```c
[[unknown::attribute(L""U"")]]int main(){}
```
The concatenation of the string literals `L""` and `U""` is invalid. In C++ the same issue exists, but a space is needed between the string literals. Only EDG gets this correct. See also https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124655
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the C reproducer in the issue and compare how Clang handles the same mixed-prefix concatenation in C++ when a space is present. Trace parsing and validation for ignored attributes, then add regression coverage showing that incompatible string literal encoding prefixes are rejected in both forms.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- c, cpp
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 48/100