EDIT: after some brief searching around, I believe .rlibs are little more than archives with rust-specific metadata and internal relocations are not resolved.
The key point in the proposal for a static-bundle-object is to properly handle static libraries as linked objects, instead of as a bunch of plain .o files.
Are there cases in which function-sections doesn't work (GCs too much) but a hypothetical "file-sections" does? For example cases in which the code relies on side effects of global constructors, but those would be left out by function-sections?
This is the current intention, as implemented in the up-to-date draft: https://github.com/bminor/binutils-gdb/commit/99aef6ba8db670.... Please note however that one would no longer need to specify the "--whole-archive" flag, hence resolving issues with potential duplicate placement of the static library in the linker's CLI.
> Are there cases in which function-sections doesn't work (GCs too much) but a hypothetical "file-sections" does? For example cases in which the code relies on side effects of global constructors, but those would be left out by function-sections?
Good question. In the first article in this series I discussed issues with global constructors and was pretty much waved away, being told that code should not be written this way. One of the members of the ELF committee did suggest an alternative for handling it yet pretty much mentioned that there are still missing pieces that require handling for their proposal to work (https://groups.google.com/g/generic-abi/c/sT25-xfX9yc/m/NRo0...).
I have to admit the pushback on ET_STAT is not completely unexpected. I can see why the gABI thread would argue that it can be solved without a new e_type. It would be a major change that requires updating all toolchains, on the consumer and producer side. It would certainly take over a decade for the support to percolate everywhere, including some of the mobile and embedded toolchains where I've had these static linking & symbol visibility issues before.
The reason I still wouldn't mind ET_STAT is that I feel it does remove some complexity in the long run by not relying on things like ar archives, their hidden members with special meaning, and their different flavors. We will still be working with ELF many decades from now, so I still see some value in doing these slow migrations that simplify the final design. I would be happy if fifty or a hundred years from now ar archives becomes history, like ELF has done to the a.out format.
That aside, there are also some interesting alternative ideas in the gABI thread (STB_LIBLOCAL is intriguing), but it seems like the path forward is through the toolchain first.
I'd consider it a very nice result if third-party tools like armerge are deprecated by upstream support in the native toolchain (but I appreciate the mention in the article!)
And thank you for continuing to work on this, really appreciate the work you've been doing there.
stabbles•4h ago
1. check whether all "undefined" symbols can be resolved in dependencies mentioned in `-l`, otherwise fail
2. store metadata of "used" libraries.
So, it would create an archive `libexample.a` containing:
where METADATA contains the search path `/somewhere/lib` and needed libraries `dep1` and `dep2`.So that ultimately when you compile and link `gcc foo.c -lexample`, the linker resolves the dependencies just like in shared linking.
eyalitki•3h ago
I hope that once integrated to linkers the adoption of this new format will help convince that it deserves significantly better tooling.