bzip2-sys and msrv

[nyonson]

I am attempting to use cargo's v3 resolver to pick dependency versions which comply with my crate's MSRV. Trying a cargo update today, the bzip2-sys dependency was bumped, but it fails to build with the 1.63 rust compiler.

Relevant dependency tree:

$ cargo tree -i bzip2-sys
bzip2-sys v0.1.13+1.0.8
└── bzip2 v0.4.4
    └── zip v0.6.6
        [build-dependencies]

My build error:

...
warning: In file included from /nix/store/1ycjq6h047qqwp3fm9sbl805xnrxlh2h-glibc-2.40-66-dev/include/bits/libc-header-start.h:33,
warning:                  from /nix/store/1ycjq6h047qqwp3fm9sbl805xnrxlh2h-glibc-2.40-66-dev/include/stdlib.h:26,
warning:                  from bzip2-1.0.8/bzlib_private.h:25,
warning:                  from bzip2-1.0.8/bzlib.c:31:
warning: /nix/store/1ycjq6h047qqwp3fm9sbl805xnrxlh2h-glibc-2.40-66-dev/include/features.h:422:4: warning: #warning _FORTIFY_SOURCE requires compiling with optimization (-O) [-Wcpp]
warning:   422 | #  warning _FORTIFY_SOURCE requires compiling with optimization (-O)
warning:       |    ^~~~~~~

error: could not compile `bzip2-sys` due to 43 previous errors

I am a little new to the whole strict MSRV thing, but would it help to tag this library with an MSRV for the v3 resolver to do its job?

[folkertdev]

well that error is in glibc, not in anything that we directly control. The bzip2-sys crate is ancient, and so to keep much older versions working we've tried to not tough it too much.

As a quick fix, does it work to use this instead?

bzip2 = { version = "0.5.2", default-features = false, features = ["libbz2-rs-sys"] }

(this uses a pure rust implementation, so it at least doesn't run into any C issues)

[nyonson]

Unfortunately my MSRV is 1.63 and looks like that version of bzip2's is 1.65

[folkertdev]

you want a very new resolver but a very old msrv?

Anyway, it looks like we, by default, select cc at version 1.1.1, which as msrv 1.67.0, so maybe we can bump it? I'd need to check that with some people though because we really don't want to break existing code if we can help it.

So, something that might work is to explicitly depend on a slightly earlier but msrv-compatible version of bzip2-sys (cargo should not duplicate the dependency in that case) and see whether that works.

[nyonson]

you want a very new resolver but a very old msrv?

Yea, I hop over to the new resolver to do the dirty work of selecting the highest dependency versions for me which comply with my MSRV (in theory?).

Anyway, it looks like we, by default, select cc at version 1.1.1, which as msrv 1.67.0, so maybe we can bump it? I'd need to check that with some people though because we really don't want to break existing code if we can help it.

So, something that might work is to explicitly depend on a slightly earlier but msrv-compatible version of bzip2-sys (cargo should not duplicate the dependency in that case) and see whether that works.

I have it working right now by tweaking the lock file with a cargo update -p bzip2-sys --precise 0.1.11+1.0.8, but was kinda curious why this dep is having issues.