Re: [RFC] building postgres with meson

Hi Andres,

> Cool. I think I pushed a fix/workaround for the issue now. Still can't decide
> whether it's apple's or meson's fault.

Many thanks! The fix solved the problem, I can compile with -Dldap=enabled now.
The code passes the tests too.

> > $ meson configure -Dldap=disabled
> > $ meson configure -Dssl=openssl
> > $ meson configure -Dprefix=/Users/eax/pginstall
>
> FYI, you can set multiple options in one go ;)

Thanks! ;)

> Makes sense. Currently we don't fill the --configure thing, because there
> configure wasn't used. We could try to generate something compatible from
> meson options, but I'm not sure that's a good plan.

If pg_config output was 100% backward compatible with Autotools one, that would
simplify the lives of the extension developers for sure. However, considering
that at PGCon we agreed that both Autotools and Meson will be maintained for
several releases, personally I wouldn't say that this compatibility is
necessary, nor is it realistically deliverable. Nevertheless, IMO there should
be a stable and documented way to determine the PostgreSQL version (this can be
done with `pg_config --version` for both Autotools and Meson), the build tool
used (no way to determine) and the build options (no way to determine
for Meson).

> I suspect the errors might be due to CC/CPPFLAGS/... not being defined. I can
> try to make it output something roughly compatible with the old output, for
> most of those I already started to compute values for the PGXS compat stuff I
> was hacking on recently.

Yes, that could explain the problem. Just for the record, I get several errors
regarding src/export.h in TimescaleDB code [1]:

```
/Users/eax/projects/c/timescaledb/src/export.h:26:5: error: pasting formed
  ')87628', an invalid preprocessing token [clang-diagnostic-error]
#if TS_EMPTY(PGDLLEXPORT)
             ^
/Users/eax/projects/c/timescaledb/src/export.h:17:22: note: expanded from
  macro 'TS_EMPTY'
#define TS_EMPTY(x) (TS_CAT(x, 87628) == 87628)
                     ^
/Users/eax/projects/c/timescaledb/src/export.h:15:23: note: expanded from
  macro 'TS_CAT'
#define TS_CAT(x, y) x##y
                      ^
/Users/eax/projects/c/timescaledb/src/export.h:26:14: error: function-like
  macro '__attribute__' is not defined [clang-diagnostic-error]
#if TS_EMPTY(PGDLLEXPORT)
             ^
/Users/eax/pginstall/include/postgresql/server/c.h:1339:21: note: expanded
  from macro 'PGDLLEXPORT'
#define PGDLLEXPORT __attribute__((visibility("default")))
                    ^
/Users/eax/projects/c/timescaledb/src/export.h:30:2: error: "PGDLLEXPORT is
  already defined" [clang-diagnostic-error]
#error "PGDLLEXPORT is already defined"
 ^
1 warning and 3 errors generated.
Error while processing /Users/eax/projects/c/timescaledb/src/extension.c
```

[1]: https://github.com/timescale/timescaledb/blob/main/src/export.h

-- 
Best regards,
Aleksander Alekseev