Ivan MolodetskikhDec 29

One thing I'm missing in the Rust ecosystem of bindings to C libraries is easy conditional compilation based on the build-time library version. Something like the GTK_CHECK_VERSION() macros in C.

In Rust bindings, it's common to expose some baseline version API, then have feature flags to expose (and depend on) newer versions of the library. But there's no simple way to do, as a downstream user:

#[cfg(have_gtk_4_12)]
use_new_api();
#[cfg(not(have_gtk_4_12))]
fallback_with_old_api();

#rust

Show threadIvan MolodetskikhDec 30

Related: how do distros track these build-time dependency checks? E.g. my app did a build-time check and used the GTK < 4.12 code path, then the distro updated GTK to 4.12, so now my app needs to be rebuilt to take advantage of the new API. How is this tracked?

I guess this question is more relevant for rolling-release distros, but it's very possible for a build-time check to test for a minor version which would be updated even in a non-rolling-release distro.

#linux #fedora

Show threadSimon JosefssonDec 30
@YaLTeR It is traditionally handled via shared libraries, and not having such static version-checks at all. That approach is going out of fad, especially in the Go/Rust eco-systems, which lead to Debian not covering Go/Rust with generic security support because the only way to fix it is to rebuild tons of packages. This is clearly not sustainable. Debian’s preference has been for Rust/Go to switch to shared libraries, but I think that effort is mostly lead by non-Go/Rust people.
Show threadIvan MolodetskikhDec 30
@jas the problem I'm talking about is orthogonal to shared vs. static libraries
Show threadIvan MolodetskikhDec 30
@jas actually you could even say it's *more* relevant when using shared libraries
Show threadSimon Josefsson
@YaLTeR If you assume shared libraries, such build-time static checks doesn’t make sense do they? You need to make runtime-decisions, because at build time you don’t know which shared library will be used. And if you do runtime-checks, things ought to work regardless of version, and distributions doesn’t have to track this in any way. Still, there is a lot of hidden complexity (and source for weird bugs) with conditional code like this.
Dec 30 at 11:32amWeb