Handling of main() function for freestanding

[Jason Merrill]

On 10/13/22 16:14, Arsen Arsenović wrote:
> On Thursday, 13 October 2022 19:24:41 CEST Jason Merrill wrote:
>> I was arguing that we don't need the new flag; there shouldn't be any
>> need to turn it off.
> At the time, I opted to go with a more conservative route; I haven't
> been around enough to have very strong opinions ;)  I certainly can't
> think of a way always adding a return can go wrong, but figured someone,
> somehow, might rely on this behavior.  Removed the flag and tested on
> x86_64-pc-linux-gnu, v3 attached.

Thanks!

> FWIW, there's precedent for treating main specially regardless of
> flag_hosted (e.g. it's always marked extern "C" in the C++ frontend,
> AFAICT).
> 
> -#define DECL_MAIN_P(NODE)				\
> +#define DECL_MAIN_FREESTANDING_P(NODE)			\
>     (DECL_EXTERN_C_FUNCTION_P (NODE)			\
>      && DECL_NAME (NODE) != NULL_TREE			\
> -    && MAIN_NAME_P (DECL_NAME (NODE))			\
> -    && flag_hosted)
> +    && MAIN_NAME_P (DECL_NAME (NODE)))
> +
> +/* Nonzero iff NODE is a declaration for `main', and we are hosted. */
> +#define DECL_MAIN_P(NODE) (DECL_MAIN_FREESTANDING_P(NODE) && flag_hosted)

I liked in the previous version that you checked the return type of main 
when !flag_hosted, here and in c_missing_noreturn_ok_p.  Let's bring 
that back.

Jason