I'll start from a failure where I found it out.
What I observed:
I had guix-0.13 installed systemwide. Then I attempted to install
guix-0.14 by unpacking/building it Bbuild failed with obscure errors
about missing required functions
Why I think it failed:
When guix-0.13 was built and installed among other things my system
got compiled file as:
'/usr/lib64/guile/2.2/site-ccache/guix/modules.go'
When I unpacked guix-0.14 it's source file timestamps were preserved
by unpack process. Specifically 'guix/modules.scm' was older than system's
'/usr/lib64/guile/2.2/site-ccache/guix/modules.go'
As a result guix build attempted to pull in parts of 0.13 release into 0.14
build process.
It looks like the main problem is in libguile/load.c:compiled_is_fresh():
https://git.savannah.gnu.org/gitweb/?p=guile.git;a=blob;f=libguile/load.c;h=e95c36db1d670f0c7091aba080e21deb53bbab4f;hb=HEAD#l558
567 if (source_mtime.tv_sec < compiled_mtime.tv_sec
568 || (source_mtime.tv_sec == compiled_mtime.tv_sec
569 && source_mtime.tv_nsec <= compiled_mtime.tv_nsec))
570 compiled_is_newer = 1;
Here 'mtime(.scm) < mtime(.go)' is enough to avoid recompilation.
The workaround:
Currently Gentoo just 'touch'es source tarball at unpacking time to guarantee
the rebuild as:
https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=651f557f9302d29aa0de5ea10ef4e575b686fb21
It is unfortunate and would require changing every package.
The build failure is easily reproducible. I can try to craft artificial
example
to ease debugging if needed.
Probable fix:
I think guile should embed/check more data about source file to hit the cache.
The examples would be:
1. size of source file
2. hash of source file contents
3. hash of parsed source file
4. use 'mtime(.scm) == mtime(.go)' as a cache hit hint (would require faking
mtime on a .go file)
Thank you!
--
Sergei
