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ziglang / zig

General-purpose programming language and toolchain for maintaining robust, optimal, and reusable software.
https://ziglang.org
MIT License
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Size saving opportunity in glibc include directories #21258

Open alexrp opened 2 months ago

alexrp commented 2 months ago

Right now, we have a directory for each glibc-based target triple under lib/libc/include. But if you do a recursive diff between many (all?) of the related ones (riscv32-linux-gnu vs riscv64-linux-gnu, arm-linux-gnueabi vs arm-linux-gnueabihf, and so on), it becomes apparent that the only difference is the presence of the appropriate lib-names-<abi>.h and stubs-<abi>.h headers. The appropriate version of this header is picked by the lib-names.h and stubs.h files based on preprocessor defines.

Also, we already have a bunch of logic for picking the right paths based on target info:

https://github.com/ziglang/zig/blob/e084c46ed6906dc51724d99b29f0992272384f5a/src/glibc.zig#L416-L663

Given these facts, I think we could enhance process_headers.zig to exploit this knowledge and merge these include directories together (while asserting for safety that there are no actual diffs between them). Then we'd just update src/glibc.zig to have very slightly smarter include directory selection.

wooster0 commented 2 months ago

Sounds a bit like https://github.com/ziglang/universal-headers?

alexrp commented 2 months ago

Not exactly. The idea there is to have a single set of headers to cover everything. Here I'm just talking about merging headers for targets when they're literally identical already.