Re: zlib detection in Meson on Windows broken?

Hi Sandeep, Nazir,

On Tue, 21 May 2024 at 10:14, Nazir Bilal Yavuz <byavuz81(at)gmail(dot)com> wrote:

> Hi,
>
> On Tue, 21 May 2024 at 10:20, Sandeep Thakkar
> <sandeep(dot)thakkar(at)enterprisedb(dot)com> wrote:
> >
> > Hi Dave,
> >
> > Is the .pc file generated after the successful build of zlib? If yes,
> then meson should be able to detect the installation ideally
>
> If meson is not able to find the .pc file automatically, using 'meson
> setup ... --pkg-config-path $ZLIB_PC_PATH' might help.
>

The problem is that on Windows there are no standard locations for a
Unix-style development library installation such as this, so the chances
are that the .pc file will point to entirely the wrong location.

For example, please see
https://github.com/dpage/winpgbuild/actions/runs/9172187335 which is a
Github action that builds a completely vanilla zlib using VC++. If you look
at the uploaded artefact containing the build output and example the .pc
file, you'll see it references /zlib as the location, which is simply where
I built it in that action. On a developer's machine that's almost certainly
not going to be where it actually ends up. For example, on the pgAdmin
build farm, the dependencies all end up in C:\build64\[whatever]. On the
similar Github action I'm building for PostgreSQL, that artefact will be
unpacked into /build/zlib.

Of course, for my own builds I can easily make everything use consistent
directories, however most people who are likely to want to build PostgreSQL
may not want to also build all the dependencies themselves as well, as some
are a lot more difficult than zlib. So what tends to happen is people find
third party builds or upstream official builds.

I would therefore argue that if the .pc file that's found doesn't provide
correct paths for us, then Meson should fall back to searching in the paths
specified on its command line for the appropriate libraries/headers (which
is what it does for OpenSSL for example, as that doesn't include a .pc
file). This is also what happens with PG16 and earlier.

One other thing I will note is that PG16 and earlier try to use the wrong
filename for the import library. For years, it's been a requirement to do
something like this: "copy \zlib\lib\zlib.lib \zlib\lib\zdll.lib" to make a
build succeed against a "vanilla" zlib build. I haven't got as far as
figuring out if the same is true with Meson yet.

--
Dave Page
pgAdmin: https://www.pgadmin.org
PostgreSQL: https://www.postgresql.org
EDB: https://www.enterprisedb.com