feat(ffi): add cargo-c support

[seanmonstar]

Probably doesn't fully work yet, but here's a start.

Closes #3786

[kpcyrd]

Works fine for me:

# Maintainer: kpcyrd <kpcyrd[at]archlinux[dot]org>

pkgname=libhyper
pkgver=1.5.1
pkgrel=1
pkgdesc="Use hyper HTTP library from languages other than Rust"
arch=('x86_64')
license=('MIT')
url='https://github.com/hyperium/hyper'
depends=(
  gcc-libs
  glibc
)
makedepends=(
  cargo-c
  rust
)
provides=('libhyper.so')
source=(https://github.com/hyperium/hyper/archive/v${pkgver}/${pkgname}-${pkgver}.tar.gz
        https://patch-diff.githubusercontent.com/raw/hyperium/hyper/pull/3787.patch
        Cargo.lock)
sha256sums=('fc043aa072c7ed39740324b250047d8ef2cfb30bff3364fabeeb150c28406ec0'
            '2c0ee5a25bf17eb874b553a9ff4b2f63dbd50ae6dcb3d39e22496ed7194f2579'
            '1696298a6307c5cc2a4eae17664cee47841ba8f6eca8b3784a3f52304b67cacf')
b2sums=('2d52a630a7e652742d5ea7df217e1db3ffea51422d5cdfcba4a88d024705bbb8d3c384636a130bdb3a53b5c3c84e8ca6f329445556e4c1c5d2a002996b956d1b'
        'bc115a621da7884e03061ce98a00db9a6b8aad7e95b36f6fa611e0baa14af54a2c26b15f8cba3381b328ba27c5c12f1f495a42664f1e6383f0bc0473868bcce1'
        '7cece9c84da0e17886c547e1008fa46680fea728b72da846529c126c126cf75d33e5f9c20b105dbd48ab88d9a164170899c0e9745cfe196bf99703e999006bd3')

prepare() {
  cd hyper-${pkgver}
  cp ../Cargo.lock .
  patch -Np1 -i ../3787.patch
  cargo fetch --locked --target "$(rustc -vV | sed -n 's/host: //p')"
}

build() {
  cd hyper-${pkgver}
  cargo cbuild --release --frozen --prefix=/usr
}

package() {
  cd hyper-${pkgver}
  cargo cinstall --release --frozen --prefix /usr --destdir "${pkgdir}"
  install -Dm644 -t "${pkgdir}/usr/share/licenses/${pkgname}" LICENSE
}

# vim: ts=2 sw=2 et:

Results in this package:

% tar tvvf libhyper-1.5.1-1-x86_64.pkg.tar.zst
-rw-r--r-- root/root      5367 2024-11-19 23:36 .BUILDINFO
-rw-r--r-- root/root       479 2024-11-19 23:36 .MTREE
-rw-r--r-- root/root       430 2024-11-19 23:36 .PKGINFO
drwxr-xr-x root/root         0 2024-11-19 23:36 usr/
drwxr-xr-x root/root         0 2024-11-19 23:36 usr/lib/
lrwxrwxrwx root/root         0 2024-11-19 23:36 usr/lib/libhyper.so -> libhyper.so.1.5.1
lrwxrwxrwx root/root         0 2024-11-19 23:36 usr/lib/libhyper.so.1 -> libhyper.so.1.5.1
-rwxr-xr-x root/root     14048 2024-11-19 23:36 usr/lib/libhyper.so.1.5.1
drwxr-xr-x root/root         0 2024-11-19 23:36 usr/lib/pkgconfig/
-rw-r--r-- root/root       287 2024-11-19 23:36 usr/lib/pkgconfig/hyper.pc
drwxr-xr-x root/root         0 2024-11-19 23:36 usr/share/
drwxr-xr-x root/root         0 2024-11-19 23:36 usr/share/licenses/
drwxr-xr-x root/root         0 2024-11-19 23:36 usr/share/licenses/libhyper/
-rw-r--r-- root/root      1062 2024-11-19 23:36 usr/share/licenses/libhyper/LICENSE

Possibly something you want to take note of: Since hyper is >= 1.0.0 it's using libhyper.so.1 as SONAME, if you want to make an ABI breaking change to the C bindings you'd either need to bump hyper to 2.0.0 (which you likely won't want to do) or configure an overwrite in cargo-c configuration (which is possible and fully supported), but this only becomes relevant when the time comes anyway.

[seanmonstar]

I don't think I have it correctly copying the header file, and trying to get the C examples to build in CI just to check it works.

As for the ABI compatibility: so far, the C API has been considered experimental, while in development with curl as a user. So I wouldn't want to make a promise yet, until we mark it as stable in both projects.

[kpcyrd]

You likely want to set this then (which I forgot is an option, as well as setting this to 2):

[package.metadata.capi.library]
version_suffix_components = 3

This sets the SONAME to libhyper.so.1.5.1 instead of libhyper.so.1, so any version change of hyper signals an ABI breakage to consumers.

When setting this to 2, the SONAME would be libhyper.so.1.5 and a 1.6.0 release of hyper would signal ABI breakage, without the need for 2.0.0 or maintaining a version override.

[milibopp]

Great to see that added. Packaging this branch with Nix using cargo-c also worked mostly fine for me.

One exception: I would have expected the test suite to pass via cargo ctest here as well:

RUSTFLAGS="--cfg hyper_unstable_ffi" cargo ctest --features ffi,http1,http2,client

It does not compile though. Presumably the integration tests are not intended to be run against a dynamic library rather than a Rust crate.

[seanmonstar]

Presumably the integration tests are not intended to be run against a dynamic library rather than a Rust crate.

Ah, that's a mistake in hyper in general, unit tests don't have the right config attributes, so it also needs the server feature enabled to run. I confirmed it works with cargo ctest. Filed #3790.

[seanmonstar]

OK, tried this locally and it's now copying over the correct header file. I removed the steps to test building the examples, I didn't want to make the makefile too complicated (that's not my expertise at all). (They're still checked in the other FFI CI job.)