Fails when LTO is enabled about cargo-show-asm HOT 17 CLOSED

Yup, it's https://github.com/V0ldek/rsonpath.

The exact command I'm running is cargo asm -p rsonpath --bin rq in the project root.

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I guess the best way to deal with LTO is to implement #174 after all. I'll look into that once I'm done messing with bpaf.

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Related ticket is this #146

As far as I remember lto means generating multiple .s files and rustc is not exposing enough information for cargo-show-asm to tell what exactly was generating this time. I guess it's time to revisit the file detection one more time :)

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The state of the other issues was unclear to me. Wasn't sure if this was accepted behavior or needed a reproduction so I made this one. If you don't want to support LTO then I would like the Readme to mention that.

Thanks for working on this project btw.

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I don't mind supporting LTO, just the way it works now it asks rustc to generate asm/lto/whatever, before LTO runs and that previous ticket was mostly about making sure it still compiles and it was compiling for me with all the lto options I tried. Will try to fix, not sure how long it will take.

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@e00E try version 0.2.14, seems to work better for me.

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Removing LTO hack seems to fix the problem and both lto=thin and lto=fat, it just works on 1.71.0... 🤔 And still does not work on 1.67.1... So probably 1.67.1 was just a temporary regression of some sort.

It probably makes sense to drop the hack and proclaim that 1.67.1 + LTO of any sort is not supported...

Decisions, decisions... 🤔

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@e00E I pushed a branch called lto, you can install it using something like cargo install --git https://github.com/pacak/cargo-show-asm --branch lto. Can you check if it fixes your problem?

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That fixes it.

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upgrade from 0.2.14 all good here too.

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I'm still getting an issue on 0.2.21 that seems related. With thin LTO when trying to disassemble a --bin target I get this:

~/rsonpath> cargo asm -p rsonpath --bin rq
warning: ignoring emit path because multiple .s files were produced

warning: `rsonpath` (bin "rq") generated 1 warning
    Finished release [optimized + debuginfo] target(s) in 0.03s

Error: Cannot locate the path to the asm file

With LTO disabled it works.

As far as I remember lto means generating multiple .s files and rustc is not exposing enough information for cargo-show-asm to tell what exactly was generating this time.

I'm thinking it's this issue, judging by "warning: ignoring emit path because multiple .s files were produced`?

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I'm still getting an issue on 0.2.21 that seems related. With thin LTO when trying to disassemble a --bin target I get this:

What version of the compiler are you using?

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What version of the compiler are you using?

Latest 1.73.0: rustc 1.73.0 (cc66ad468 2023-10-03)
Fails on current nightly as well: rustc 1.75.0-nightly (bf9a1c8a1 2023-10-08)

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Hmm... Is the repo publicly available?

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Interestingly enough cargo asm -p rsonpath --bin rq --profile distribution works...

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May it be because codegen-units = 1?

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Most likely, but I'm passing codegen-units = 1 regardless so it probably means rustc ignores this with lto = thin 🤔

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