Re: MinGW compiler warnings in ecpg tests

On Fri, Nov 10, 2023 at 9:00 PM Hayato Kuroda (Fujitsu)
<kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
> Sorry for reviving the old thread. While trying to build postgres on msys2 by meson,
> I faced the same warning. The OS is Windows 10.

Yeah. This warning is visible on CI, and on fairywren since its MSYS2
upgrade a couple of months ago. Old MinGW didn't like %lld (I think
perhaps the printf from msvcrt.dll from 1996 didn't like it and MinGW
knew that), but new MinGW doesn't like %I64d (that's interesting, but
not relevant here because %lld is clearly the correct format string,
and it works). We should just revert that change. Here's a patch.

That leaves only three more annoying warnings:

../pgsql/src/backend/postmaster/postmaster.c:857:31: warning:
'__p__environ' redeclared without dllimport attribute: previous
dllimport ignored [-Wattributes]
857 | extern char **environ;

Those were there before the upgrade. POSIX says that environ should
not be declared by a header, but Windows apparently declares it, or at
least its cousin _environ, in <stdlib.h> which we include in c.h. I
have no idea why Visual Studio doesn't warn, or why the documentation
only tells you about _environ and not environ, or where the macro (?)
comes from that renames it, but it passes CI and is
warning-free on both toolchains if you just hide the offending
declarations.