Re: meson: Add support for building with precompiled headers

Andres Freund <andres@anarazel.de> writes:
> When using precompiled headers we cannot override macros in system headers
> from within .c files, as headers are already processed before the #define in
> the C file is reached.

> A few files #define FD_SETSIZE 1024 on windows, as the default is only 64. I
> am hesitant to change FD_SETSIZE globally on windows, due to
> src/backend/port/win32/socket.c using it to size on-stack arrays. Instead add
> -DFD_SETSIZE=1024 when building the specific targets needing it.

Color me confused, but how does it work to #define that from the command
line if it can't be overridden from within the program?

            regards, tom lane