| Issue |
52944
|
| Summary |
Wc++20-designator gives warnings from macros defined in system headers
|
| Labels |
clang:frontend
|
| Assignees |
|
| Reporter |
carlosgalvezp
|
Hi,
I find that `-Wc++20-designator` (which I get via `-pedantic`) is giving warnings from system headers, which is strange and inconsistent with GCC. The point of system headers is to suppress warnings from them in a clean way - system headers are not to be patched by users, so warnings cannot be acted upon. Currently we need to suppress warnings to the whole .cpp file that includes such a header due to warnings from system macros not being ignored, which may lower the quality of the whole file.
I have asked in [cfe-dev](https://reviews.llvm.org/D116378) without answer, and posted in [StackOverflow](https://stackoverflow.com/questions/70488470/how-to-ignore-compiler-warnings-for-macros-defined-in-third-party-headers) where I got feedback that this is most likely a bug, so I'm raising it here.
Example code that doesn't give warnings in GCC (9.4.0), but does in Clang (14.0.0):
```cpp
// include/third_party2.h
#pragma once
struct Foo
{
int x;
int y;
};
#define FOO Foo{.x = 123, .y = 321}
```
```cpp
// main2.cpp
#include <third_party2.h>
int main()
{
Foo f = FOO;
return f.x;
}
```
```cpp
$ g++ -isystem include -pedantic main2.cpp
$
```
```cpp
$ clang++ -isystem include -pedantic main2.cpp
main2.cpp:5:13: warning: designated initializers are a C++20 extension [-Wc++20-designator]
Foo f = FOO;
^
include/third_party2.h:9:17: note: expanded from macro 'FOO'
#define FOO Foo{.x = 123, .y = 321}
^
1 warning generated.
```
Does this make sense? I'm happy to fix it myself but I need some guidance.
Thanks!
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