Warnings emitted when utilizing -pedantic -save-temps flags.

[milos1397]

int main(void)
{
    return 0;
}

when compiled with -pedantic -save-temps flags:

clang test.c -O3 -S  -Wall -pedantic -save-temps

causes the following warnings, regarding usage of GNU line directives, to appear:

example.i:1:5: warning: this style of line directive is a GNU extension [-Wgnu-line-marker] 
# 1 "<source>"
<source>:1:5: warning: this style of line directive is a GNU extension [-Wgnu-line-marker]
# 1 "<built-in>" 1
    ^
2 warnings generated.

(you can see it here https://godbolt.org/z/ffMePa77o)

This is because Clang has some hardcoded GNU line directives, which it adds during preprocessing in the function clang::InitializePreprocessor.

Can they be cleaned?

[shafik]

Maybe related: #63284

CC @AaronBallman

[AaronBallman]

Yeah, this seems like a slightly different facet to the issue in #63284 (same problem, just with different line markers).

[llvmbot]

@llvm/issue-subscribers-clang-frontend

```cpp int main(void) { return 0; } ```

when compiled with -pedantic -save-temps flags:

clang test.c -O3 -S  -Wall -pedantic -save-temps

causes the following warnings, regarding usage of GNU line directives, to appear:

example.i:1:5: warning: this style of line directive is a GNU extension [-Wgnu-line-marker] 
# 1 "<source>"
<source>:1:5: warning: this style of line directive is a GNU extension [-Wgnu-line-marker]
# 1 "<built-in>" 1
    ^
2 warnings generated.

(you can see it here https://godbolt.org/z/ffMePa77o)

This is because Clang has some hardcoded GNU line directives, which it adds during preprocessing in the function clang::InitializePreprocessor.

Can they be cleaned?