configure --with-protobuf-lib / --with-protobufdir broken

[tbussmann]

Currently it is not possible to compile PostGIS with protobuf-c by specifying the path to the library using --with-protobuf-lib= or --with-protobufdir=, only if the installation can be found by pkg-config it can be overridden by PROTOBUFC_LIBS. Effectively, the -lprotobuf-c is missing in LDFLAGS.

The first option broke by commit [6eeee128815/git] as an attempt to fix #4964. Part of this change broke building with pkg-config as its output was now overwritten and thus the -L went missing which resulted in #4977. That again was fixed by an attempt to roll back the first change by [86a8a5979/git]. Unfortunately that finally broke --with-protobufdir and resulted in the current situation.

To fix, we need to add -lprotobuf-c back to line source:git/configure.ac@98c1ed85#L1031​ and source:git/configure.ac@98c1ed85#L1043​.

For the original issue, #4964 I can imagine to further develop the idea from the first attempt but guard that a bit by replacing source:git/configure.ac@98c1ed85#L1062​ with something like that:

	[if test "x$PROTOBUF_LDFLAGS" = "x"; then
		PROTOBUF_LDFLAGS="-lprotobuf-c"
	fi],

[tbussmann]

as I haven't contributed before - would it be preferred to send a .patch or raise a pull request on GitHub for issues like this? Edit: I've looked around a bit and it seems GitHub is a usual way these days. Unfortunately, the nice CI integration will likely not cover this corner case. Here are my Pull Requests: ​https://github.com/postgis/postgis/pull/662 and ​https://github.com/postgis/postgis/pull/663

[strk]

tbussmann: you can file pull requests on the official repository ( ​https://git.osgeo.org/gitea/postgis/postgis ) or on any of the mirrors (github included, so your PR is ok)

It would be nice to add CI checking for corner cases, we love having more bots :)

[robe]

I'm going to give your pull request on my local and accept if it doesn't break my build. Unfortunately I'm not sure how to test this corner case.

[Regina Obe <lr@…>]

In 4053205/git:

Patches from Tobias Bussmann
References #5090 for PostGIS 3.3.0
Closes ​https://github.com/postgis/postgis/pull/662, Closes
​https://github.com/postgis/postgis/pull/663atches from Tobias Bussmann
References #5090 for PostGIS 3.3.0
Closes ​https://github.com/postgis/postgis/pull/662, Closes ​https://github.com/postgis/postgis/pull/663

[Regina Obe <lr@…>]

In ecad675/git:

Closes #5090 for PostGIS 3.2.1
Closes #5091 for PostGIS 3.2.1
Fix --with-protobuf-lib / --with-protobufdir broken
References ​https://github.com/postgis/postgis/pull/662
References ​https://github.com/postgis/postgis/pull/663

[tbussmann]

thanks for applying the patches!

Unfortunately I'm not sure how to test this corner case.

Something among the following may work:

• configure postgis with the --with-protobufdir or --with-protobuf-lib/--with-protobuf-inc set to your protobuf-c installation
• without the first patch, the configure will be successful but the build will fail.
• apply the first patch, repeat configure, verify that it now builds

For the second patch (original intention of #4964):

• remove the libprotobuf-c.pc from your pkgconfig directory
• make sure the protobuf-c library can be found in your default lib / include paths
• configure postgis w/o any protbuf related parameters.
• without the second patch, the configure will be successful but the build will fail.
• apply the second patch, repeat configure, verify that it now builds

Make sure this does not interfere with pkg-config builds (#4977)

• move the libprotobuf-c.pc file back to your pkgconfig directory
• configure postgis w/o any protbuf related parameters.
• with the patches applied, configure and build should still be successful (I think, that was already verified by the CI)