| Issue |
138100
|
| Summary |
[clang] `clang diagnostic` breaks `_Pragma`
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
Eisenwave
|
https://godbolt.org/z/bsjasnK8T
```cpp
#define DO_PRAGMA_(...) _Pragma(#__VA_ARGS__)
#define DO_PRAGMA(...) DO_PRAGMA_(__VA_ARGS__)
#define DIAGNOSTIC_IGNORED(...) DO_PRAGMA(clang diagnostic ignored __VA_ARGS__)
DIAGNOSTIC_IGNORED(-Wdeprecated)
```
This doesn't work and produces the error:
```
clang++: warning: argument unused during compilation: '-S' [-Wunused-command-line-argument]
<source>:6:1: error: expected string literal in pragma diagnostic
6 | DIAGNOSTIC_IGNORED(-Wdeprecated)
| ^
<source>:4:33: note: expanded from macro 'DIAGNOSTIC_IGNORED'
4 | #define DIAGNOSTIC_IGNORED(...) DO_PRAGMA(clang diagnostic ignored __VA_ARGS__)
| ^
<source>:2:24: note: expanded from macro 'DO_PRAGMA'
2 | #define DO_PRAGMA(...) DO_PRAGMA_(__VA_ARGS__)
| ^
<source>:1:25: note: expanded from macro 'DO_PRAGMA_'
1 | #define DO_PRAGMA_(...) _Pragma(#__VA_ARGS__)
| ^
<scratch space>:5:27: note: expanded from here
5 | clang diagnostic ignored -Wdeprecated
|
```
If we instead write
```cpp
#define DIAGNOSTIC_IGNORED(...) DO_PRAGMA(lmao __VA_ARGS__)
```
The code is preprocessed as expected, and the `-E` output is:
```cpp
#pragma lmao -Wdeprecated
```
Such uses of `_Pragma` ough to be valid.
The error is specific to `clang diagnostic` inside `_Pragma`. If we write `clang dogs` instead, it works.
GCC accepts this code (with `GCC diagnostic` of course).
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