this post was submitted on 23 Jan 2025
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11
Auto debloat unused pub items from dependencies. (infosec.pub)
submitted 4 weeks ago* (last edited 3 weeks ago) by Doods@infosec.pub to c/rust@programming.dev
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I shaved off 10 MiB from my binary in 2 hours!

I made a program using Macroquad, then I built it in release mode, the binary was 63 MiB in size.

So I used cargo vendor to have a better look at Macroquad and one of its dependencies, glam.

I then started to delete code, like, lots and lots of code(about 30_000 lines of code); none of it affected my main project, some of it became 'dead_code' just by removing the pub keyword.

The result is that my project was unaffected and the binary went down to 52 MiB.

Is there a way to automate removal of unneeded elements from dependencies? This is potentially huge.

EDIT: I FIGURED IT OUT!!!

My mistake was measuring the size of "target/release", I discovered that that folder contains many "unnecessary" files, like "deps", which greatly bloat the folder'r size, the actual size of my binary is 864K.

I am so relieved.

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[–] KillTheMule@programming.dev 9 points 4 weeks ago (3 children)

Actually, dead code eliminination should do the trick, if you're compiling a binary at least (same for a library I think, but there could be re-exports there). Did you compile in release mode?

[–] Starfighter@discuss.tchncs.de 3 points 4 weeks ago* (last edited 4 weeks ago) (1 children)

To expand: Just configure whatever profile you're using (dev, release, ...) to have link time optimization (lto) enabled:

[profile.release]
lto = "fat"

Reference

[–] Doods@infosec.pub 1 points 4 weeks ago* (last edited 4 weeks ago)

This really doesn't seem to do the trick, the binary's still at 63MiB.

Also "fat" and true are identical.

Edit: I'm not sure I replied to the right person, ignore this.

[–] quilan@lemmy.world 1 points 4 weeks ago

I don't recall what the default behavior is with the linker, but it might also benefit from at least thin LTO.

[–] Doods@infosec.pub 1 points 4 weeks ago (1 children)

The compiler doesn't consider it to be dead code since it's marked pub.

[–] KillTheMule@programming.dev 3 points 4 weeks ago (1 children)

Sure, but isn't this in a dependency? Can't be reached when only importing your crate anyways? And if you're building a binary, I don't think this could really considered exported, is what I mean :)

[–] Doods@infosec.pub 1 points 4 weeks ago

Yes that's exactly what I want. The compiler should stop considering it accessible.