Fails when LTO is enabled
e00E opened this issue · 17 comments
./b/Cargo.toml:
[package]
name = "b"
version = "0.1.0"
edition = "2021"
[dependencies]
a = { path = "../a" }
[profile.release]
lto = "thin"
./b/src/main.rs:
fn main() {
a::foo();
}
./a/src/lib.rs:
pub fn foo() {}
./a/Cargo.toml:
[package]
name = "a"
version = "0.1.0"
edition = "2021"
[dependencies]
Enter the b directory. cargo check works. cargo asm fails with a long error that ends with:
... -Wl,-Bdynamic" "-lgcc_s" "-lutil" "-lrt" "-lpthread" "-lm" "-ldl" "-lc" "-Wl,--eh-frame-hdr" "-Wl,-z,noexecstack" "-L" "/home/a/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-o" "/home/a/b/target/release/deps/b-a3de2d2ccfd03dbf" "-Wl,--gc-sections" "-pie" "-Wl,-z,relro,-z,now" "-Wl,-O1" "-nodefaultlibs"
= note: /usr/bin/ld: /home/a/b/target/release/deps/liba-ea018d38ebe9b07c.rlib: error adding symbols: file format not recognized
collect2: error: ld returned 1 exit status
Succeeds with lto = "off", lto = false. Fails with lto = "thin", lto = "fat". See the Cargo documentation for more information on LTO.
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 :)
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.
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.
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... 🤔
@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?
That fixes it.
upgrade from 0.2.14 all good here too.
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 fileWith 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`?
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?
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)
Hmm... Is the repo publicly available?
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.
Interestingly enough cargo asm -p rsonpath --bin rq --profile distribution works...
May it be because codegen-units = 1?
Most likely, but I'm passing codegen-units = 1 regardless so it probably means rustc ignores this with lto = thin 🤔