Bitcoin Core `configure` fails after #1084 was merged

[dhruv]

Bitcoin Core's secp subtree is currently at 44c2452fd387f7ca604ab42d73746e7d3a44d8a2. Updating the subtree to cd470333351bd6d90296352f2a957f38bbdaf014 (merging #1084) causes Bitcoin Core CI failure as it cannot run the config scripts anymore as seen here

I don't know much about build systems, but am happy to learn and help with guidance.

[real-or-random]

Hmmm.... So apparently Core's CI sets some explicit cache file that caches some configuration values:
https://cirrus-ci.com/task/6310546097045504?logs=ci#L478-L485

I have never really used explicit cache files, but the error message tells us that the file is outdated. So I believe this is not an issue in our repo. Let me ask the Core build system experts on IRC.

[real-or-random]

Hmmm.... So apparently Core's CI sets some explicit cache file that caches some configuration values:

Hm no, so this done automatically by autoconf when running AC_CONFIG_SUBDIRS. And IIUC then it complains that the environment has changed in between the two configure runs (core and secp256k1), namely

configure: error: `PKG_CONFIG_PATH' was not set in the previous run

@dhruv Can you test #1090? I suspect that to be the issue instead of #1084 but I could be wrong.

[real-or-random]

Okay, so I believe this is the reason:

https://github.com/bitcoin/bitcoin/blob/948f5ba6363fcc64f95fed3f04dbda3d50d61827/depends/config.site.in#L87-L93

These were added in the same PR as this commit which implemented the unexport.
bitcoin/bitcoin@0dc8613
But the code added by this commit was removed apparently, probably because it "just worked" as long as secp256k1 also used pkgconf... (can't find the commit right now...) I believe it should be brought back...

"sigh", indeed.

cc @theuni

[real-or-random]

This is the bad commit:
bitcoin/bitcoin@ee30bf7

@dhruv Can you try if CI passes if you revert this? (I guess a local depends build will do the job too, if this is easier than running CI).

edit: ok, sorry, this would work. But since only secp256k1 was using this stuff, the proper fix is just to remove those lines here entirely: https://github.com/bitcoin/bitcoin/blob/948f5ba6363fcc64f95fed3f04dbda3d50d61827/depends/config.site.in#L85-L94

[real-or-random]

edit: ok, sorry, this would work. But since only secp256k1 was using this stuff, the proper fix is just to remove those lines here entirely: bitcoin/bitcoin@948f5ba/depends/config.site.in#L85-L94

bitcoin/bitcoin#25655 taught me I'm wrong, so I believe the right fix is to revert bitcoin/bitcoin@ee30bf7. @dhruv Could you try if this makes the subtree update work?

[dhruv]

Verified that this works now: https://github.com/dhruv/bitcoin-core-ci/pull/14/checks

Thanks, @real-or-random !