On Wednesday, August 7, 2024 5:21 PM, brian m. carlson wrote: >On 2024-08-07 at 18:21:28, Josh Steadmon wrote: >> Introduce cgit-rs, a Rust wrapper crate that allows Rust code to call >> functions in libgit.a. This initial patch defines build rules and an >> interface that exposes user agent string getter functions as a proof >> of concept. A proof-of-concept library consumer is provided in >> contrib/cgit-rs/src/main.rs. This executable can be run with `cargo >> run` >> >> Symbols in cgit can collide with symbols from other libraries such as >> libgit2. We avoid this by first exposing library symbols in >> public_symbol_export.[ch]. These symbols are prepended with "libgit_" >> to avoid collisions and set to visible using a visibility pragma. In >> build.rs, Rust builds contrib/cgit-rs/libcgit.a, which also contains >> libgit.a and other dependent libraries, with -fvisibility=hidden to >> hide all symbols within those libraries that haven't been exposed with >> a visibility pragma. > >I think this is a good idea. It's optional and it allows us to add functionality as we go >along. Platforms that don't have Rust can just omit building it. > >> +[dependencies] >> +libc = "0.2.155" > >I don't love that we're using libc here. It would be better to use rustix because that >provides safe APIs that are compatible with POSIX, but I think for now we need this >because rustix doesn't offer memory management like free(3). I'd really prefer that >we didn't have to do memory management in Rust, but maybe that can come in >with a future series. This is a good point. Libc is not portable, but because I can't build with RUST anyway, I hope that libc is restricted to this facility if used. It should not be included in the git C build. It is probably moot for me anyway for this series, but I have to mention it in case anyone else gets the idea to include it as a dependency for git C. >libc also comes with the downside that it calls the actual libc functions, so you have >to write things like stat64 on Linux if you want a 64-bit stat, but that doesn't exist >on some of the BSDs, so you have to write something else and compile it >conditionally, and all of that makes the portability of it worse than with C. > >In any event, I have the intention to send a patch to replace libc with rustix in the >future if this series lands. > >> diff --git a/contrib/cgit-rs/public_symbol_export.c >> b/contrib/cgit-rs/public_symbol_export.c >> new file mode 100644 >> index 0000000000..3d1cd6cc4f >> --- /dev/null >> +++ b/contrib/cgit-rs/public_symbol_export.c >> @@ -0,0 +1,20 @@ >> +// Shim to publicly export Git symbols. These must be renamed so that >> +the // original symbols can be hidden. Renaming these with a >> +"libgit_" prefix also // avoid conflicts with other libraries such as libgit2. >> + >> +#include "contrib/cgit-rs/public_symbol_export.h" >> +#include "version.h" >> + >> +#pragma GCC visibility push(default) > >I assume this also works in clang? >-- >brian m. carlson (they/them or he/him) >Toronto, Ontario, CA
