Is `__GNUC__` defined in dmd when using importC?

[Dejan Lekic]

On Friday, 10 October 2025 at 08:34:15 UTC, felixfxu wrote:
> Hi,
>
> I'm testing dmd's _importC_ in Ubuntu 24.04, my .c/.h code has 
> many code specific to compilers, like
>
>     #ifdef __GNUC__
>
> I'm surprise to see that it seems like `__GNUC__` is defined in 
> dmd.

Reading the https://dlang.org/spec/importc.html will help you 
solve the mystery. This section in particular: 
https://dlang.org/spec/importc.html#preprocessor