Instructions missing from naked_asm blocks. #139407
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A-incr-comp
Area: Incremental compilation
C-bug
Category: This is a bug.
I-unsound
Issue: A soundness hole (worst kind of bug), see: https://en.wikipedia.org/wiki/Soundness
P-high
High priority
regression-from-stable-to-nightly
Performance or correctness regression from stable to nightly.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
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cc @folkertdev |
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@ZiCog: The code that you shared is identical. I assume you meant to write |
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I also can't seem to reproduce the bug on either |
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Sorry, you are right, that should be I just did a OS = Sequoia 15.3.1 Problem is still here for me. |
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@ZiCog: I'm trying to understand anything about what could be different between my attempt to reproduce the bug here and your setup. Is there anything special about your Is there anything special about your setup? Does it reproduce on a fresh Could you share any other information here? |
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I was using the Zed editor and Warp terminal. I have now repeated the experiment with vim and the regular Mac terminal. It turns out that starting with a new project BUT. Then editing that In short. On a fresh project there is no problem. On a "stale" project there is. My Cargo.toml remains as generated: |
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Ah, thanks @ZiCog. Repeating |
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I just tried this on an Nvidia Jetson Nano with 2025-04-04 and the problem did not show: $ cat /etc/issue $ uname -a $ rustc --version --verbose |
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Is there any way I can get a more recent nightly installed on my Mac Book Pro M1 ? |
You need to remove the
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I don't believe this has anything to do with My rough explanation for why this occurs is: Session 1 begins
Session 2 begins
Session 3 begins
I can actually reproduce this on linux with |
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OK. I now have the most recent nightly installed and it also shows the problem on my Mac M1 How did you get the problem to manifest on Linux ? |
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Prepend temp files with per-invocation random string to avoid temp filename conflicts rust-lang#139407 uncovered a very subtle unsoundness with incremental codegen, failing compilation sessions (due to assembler errors), and the "prefer hard linking over copying files" strategy we use in the compiler for file management. Specifically, imagine we're building a single file 3 times, all with `-Csave-temps -Cincremental=...`. Let's call the object file we're building for the codegen unit for `main` "`XXX.o`" just for clarity since it's probably some gigantic hash name: ``` #[inline(never)] #[cfg(any(rpass1, rpass3))] fn a() -> i32 { 0 } #[cfg(any(cfail2))] fn a() -> i32 { 1 } fn main() { evil::evil(); assert_eq!(a(), 0); } mod evil { #[cfg(any(rpass1, rpass3))] pub fn evil() { unsafe { std::arch::asm!("/* */"); } } #[cfg(any(cfail2))] pub fn evil() { unsafe { std::arch::asm!("missing"); } } } ``` Session 1 (`rpass1`): * Type-check, borrow-check, etc. * Serialize the dep graph to the incremental working directory `.../s-...-working/`. * Codegen object file to a temp file `XXX.rcgu.o` which is spit out in the cwd. * Hard-link[^1] `XXX.rcgu.o` to the incremental working directory `.../s-...-working/XXX.o`. * Save-temps option means we don't delete `XXX.rgcu.o`. * Link the binary and stuff. * Finalize[^2] the working incremental session by renaming `.../s-...-working` to ` s-...-asjkdhsjakd` (some other finalized incr comp session dir name). Session 2 (`cfail2`): * Load artifacts from the previous *finalized* incremental session, namely the dep graph. * Type-check, borrow-check, etc. since the file has changed, so most dep graph nodes are red. * Serialize the dep graph to the incremental working directory `.../s-...-working/`. * Codegen object file to a temp file `XXX.rcgu.o`. **HERE IS THE PROBLEM**: The hard-link is still set up to point to the inode from `XXX.o` from the first session, so this also modifies the `XXX.o` in the previous finalized session directory. * Codegen emits an error b/c `missing` is not an instruction, so we abort before finalizing the incremental session. Specifically, this means that the *previous* session is the last finalized session. Session 3 (`rpass3`): * Load artifacts from the previous *finalized* incremental session, namely the dep graph. NOTE that this is from session 1. * All the dep graph nodes are green since we are basically replaying session 1. * codegen object file `XXX.o`, which is detected as *reused* from session 1 since dep nodes were green. That means we **reuse** `XXX.o` which had been dirtied from session 2. * Link the binary and stuff. This results in a binary which reuses some of the build artifacts from session 2, but thinks it's from session 1. At this point, I hope it's clear to see that the incremental results from session 1 were dirtied from session 2, but we reuse them as if session 1 was the previous (finalized) incremental session we ran. This is at best really buggy, and at worst **unsound**. This isn't limited to `-C save-temps`, since there are other combinations of flags that may keep around temporary files (hard linked) in the working directory (like `-C debuginfo=1 -C split-debuginfo=unpacked` on darwin, for example). --- This PR implements a fix which is to prepend temp filenames with a random string that is generated per invocation of rustc. This string is not *deterministic*, but temporary files are transient anyways, so I don't believe this is a problem. That means that temp files are now something like... `{crate-name}.{cgu}.{invocation_temp}.rcgu.o`, where `{invocation_temp}` is the new temporary string we generate per invocation of rustc. Fixes rust-lang#139407 [^1]: https://github.com/rust-lang/rust/blob/175dcc7773d65c1b1542c351392080f48c05799f/compiler/rustc_fs_util/src/lib.rs#L60 [^2]: https://github.com/rust-lang/rust/blob/175dcc7773d65c1b1542c351392080f48c05799f/compiler/rustc_incremental/src/persist/fs.rs#L1-L40
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Apr 12, 2025
Prepend temp files with per-invocation random string to avoid temp filename conflicts rust-lang/rust#139407 uncovered a very subtle unsoundness with incremental codegen, failing compilation sessions (due to assembler errors), and the "prefer hard linking over copying files" strategy we use in the compiler for file management. Specifically, imagine we're building a single file 3 times, all with `-Csave-temps -Cincremental=...`. Let's call the object file we're building for the codegen unit for `main` "`XXX.o`" just for clarity since it's probably some gigantic hash name: ``` #[inline(never)] #[cfg(any(rpass1, rpass3))] fn a() -> i32 { 0 } #[cfg(any(cfail2))] fn a() -> i32 { 1 } fn main() { evil::evil(); assert_eq!(a(), 0); } mod evil { #[cfg(any(rpass1, rpass3))] pub fn evil() { unsafe { std::arch::asm!("/* */"); } } #[cfg(any(cfail2))] pub fn evil() { unsafe { std::arch::asm!("missing"); } } } ``` Session 1 (`rpass1`): * Type-check, borrow-check, etc. * Serialize the dep graph to the incremental working directory `.../s-...-working/`. * Codegen object file to a temp file `XXX.rcgu.o` which is spit out in the cwd. * Hard-link[^1] `XXX.rcgu.o` to the incremental working directory `.../s-...-working/XXX.o`. * Save-temps option means we don't delete `XXX.rgcu.o`. * Link the binary and stuff. * Finalize[^2] the working incremental session by renaming `.../s-...-working` to ` s-...-asjkdhsjakd` (some other finalized incr comp session dir name). Session 2 (`cfail2`): * Load artifacts from the previous *finalized* incremental session, namely the dep graph. * Type-check, borrow-check, etc. since the file has changed, so most dep graph nodes are red. * Serialize the dep graph to the incremental working directory `.../s-...-working/`. * Codegen object file to a temp file `XXX.rcgu.o`. **HERE IS THE PROBLEM**: The hard-link is still set up to point to the inode from `XXX.o` from the first session, so this also modifies the `XXX.o` in the previous finalized session directory. * Codegen emits an error b/c `missing` is not an instruction, so we abort before finalizing the incremental session. Specifically, this means that the *previous* session is the last finalized session. Session 3 (`rpass3`): * Load artifacts from the previous *finalized* incremental session, namely the dep graph. NOTE that this is from session 1. * All the dep graph nodes are green since we are basically replaying session 1. * codegen object file `XXX.o`, which is detected as *reused* from session 1 since dep nodes were green. That means we **reuse** `XXX.o` which had been dirtied from session 2. * Link the binary and stuff. This results in a binary which reuses some of the build artifacts from session 2, but thinks it's from session 1. At this point, I hope it's clear to see that the incremental results from session 1 were dirtied from session 2, but we reuse them as if session 1 was the previous (finalized) incremental session we ran. This is at best really buggy, and at worst **unsound**. This isn't limited to `-C save-temps`, since there are other combinations of flags that may keep around temporary files (hard linked) in the working directory (like `-C debuginfo=1 -C split-debuginfo=unpacked` on darwin, for example). --- This PR implements a fix which is to prepend temp filenames with a random string that is generated per invocation of rustc. This string is not *deterministic*, but temporary files are transient anyways, so I don't believe this is a problem. That means that temp files are now something like... `{crate-name}.{cgu}.{invocation_temp}.rcgu.o`, where `{invocation_temp}` is the new temporary string we generate per invocation of rustc. Fixes rust-lang/rust#139407 [^1]: https://github.com/rust-lang/rust/blob/175dcc7773d65c1b1542c351392080f48c05799f/compiler/rustc_fs_util/src/lib.rs#L60 [^2]: https://github.com/rust-lang/rust/blob/175dcc7773d65c1b1542c351392080f48c05799f/compiler/rustc_incremental/src/persist/fs.rs#L1-L40
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Yay! Confirmed. The problem no long occurs on latest nightly. Thanks to @compiler-errors and all concerned. |
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Prepend temp files with per-invocation random string to avoid temp filename conflicts rust-lang/rust#139407 uncovered a very subtle unsoundness with incremental codegen, failing compilation sessions (due to assembler errors), and the "prefer hard linking over copying files" strategy we use in the compiler for file management. Specifically, imagine we're building a single file 3 times, all with `-Csave-temps -Cincremental=...`. Let's call the object file we're building for the codegen unit for `main` "`XXX.o`" just for clarity since it's probably some gigantic hash name: ``` #[inline(never)] #[cfg(any(rpass1, rpass3))] fn a() -> i32 { 0 } #[cfg(any(cfail2))] fn a() -> i32 { 1 } fn main() { evil::evil(); assert_eq!(a(), 0); } mod evil { #[cfg(any(rpass1, rpass3))] pub fn evil() { unsafe { std::arch::asm!("/* */"); } } #[cfg(any(cfail2))] pub fn evil() { unsafe { std::arch::asm!("missing"); } } } ``` Session 1 (`rpass1`): * Type-check, borrow-check, etc. * Serialize the dep graph to the incremental working directory `.../s-...-working/`. * Codegen object file to a temp file `XXX.rcgu.o` which is spit out in the cwd. * Hard-link[^1] `XXX.rcgu.o` to the incremental working directory `.../s-...-working/XXX.o`. * Save-temps option means we don't delete `XXX.rgcu.o`. * Link the binary and stuff. * Finalize[^2] the working incremental session by renaming `.../s-...-working` to ` s-...-asjkdhsjakd` (some other finalized incr comp session dir name). Session 2 (`cfail2`): * Load artifacts from the previous *finalized* incremental session, namely the dep graph. * Type-check, borrow-check, etc. since the file has changed, so most dep graph nodes are red. * Serialize the dep graph to the incremental working directory `.../s-...-working/`. * Codegen object file to a temp file `XXX.rcgu.o`. **HERE IS THE PROBLEM**: The hard-link is still set up to point to the inode from `XXX.o` from the first session, so this also modifies the `XXX.o` in the previous finalized session directory. * Codegen emits an error b/c `missing` is not an instruction, so we abort before finalizing the incremental session. Specifically, this means that the *previous* session is the last finalized session. Session 3 (`rpass3`): * Load artifacts from the previous *finalized* incremental session, namely the dep graph. NOTE that this is from session 1. * All the dep graph nodes are green since we are basically replaying session 1. * codegen object file `XXX.o`, which is detected as *reused* from session 1 since dep nodes were green. That means we **reuse** `XXX.o` which had been dirtied from session 2. * Link the binary and stuff. This results in a binary which reuses some of the build artifacts from session 2, but thinks it's from session 1. At this point, I hope it's clear to see that the incremental results from session 1 were dirtied from session 2, but we reuse them as if session 1 was the previous (finalized) incremental session we ran. This is at best really buggy, and at worst **unsound**. This isn't limited to `-C save-temps`, since there are other combinations of flags that may keep around temporary files (hard linked) in the working directory (like `-C debuginfo=1 -C split-debuginfo=unpacked` on darwin, for example). --- This PR implements a fix which is to prepend temp filenames with a random string that is generated per invocation of rustc. This string is not *deterministic*, but temporary files are transient anyways, so I don't believe this is a problem. That means that temp files are now something like... `{crate-name}.{cgu}.{invocation_temp}.rcgu.o`, where `{invocation_temp}` is the new temporary string we generate per invocation of rustc. Fixes rust-lang/rust#139407 [^1]: https://github.com/rust-lang/rust/blob/175dcc7773d65c1b1542c351392080f48c05799f/compiler/rustc_fs_util/src/lib.rs#L60 [^2]: https://github.com/rust-lang/rust/blob/175dcc7773d65c1b1542c351392080f48c05799f/compiler/rustc_incremental/src/persist/fs.rs#L1-L40
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Prepend temp files with per-invocation random string to avoid temp filename conflicts rust-lang/rust#139407 uncovered a very subtle unsoundness with incremental codegen, failing compilation sessions (due to assembler errors), and the "prefer hard linking over copying files" strategy we use in the compiler for file management. Specifically, imagine we're building a single file 3 times, all with `-Csave-temps -Cincremental=...`. Let's call the object file we're building for the codegen unit for `main` "`XXX.o`" just for clarity since it's probably some gigantic hash name: ``` #[inline(never)] #[cfg(any(rpass1, rpass3))] fn a() -> i32 { 0 } #[cfg(any(cfail2))] fn a() -> i32 { 1 } fn main() { evil::evil(); assert_eq!(a(), 0); } mod evil { #[cfg(any(rpass1, rpass3))] pub fn evil() { unsafe { std::arch::asm!("/* */"); } } #[cfg(any(cfail2))] pub fn evil() { unsafe { std::arch::asm!("missing"); } } } ``` Session 1 (`rpass1`): * Type-check, borrow-check, etc. * Serialize the dep graph to the incremental working directory `.../s-...-working/`. * Codegen object file to a temp file `XXX.rcgu.o` which is spit out in the cwd. * Hard-link[^1] `XXX.rcgu.o` to the incremental working directory `.../s-...-working/XXX.o`. * Save-temps option means we don't delete `XXX.rgcu.o`. * Link the binary and stuff. * Finalize[^2] the working incremental session by renaming `.../s-...-working` to ` s-...-asjkdhsjakd` (some other finalized incr comp session dir name). Session 2 (`cfail2`): * Load artifacts from the previous *finalized* incremental session, namely the dep graph. * Type-check, borrow-check, etc. since the file has changed, so most dep graph nodes are red. * Serialize the dep graph to the incremental working directory `.../s-...-working/`. * Codegen object file to a temp file `XXX.rcgu.o`. **HERE IS THE PROBLEM**: The hard-link is still set up to point to the inode from `XXX.o` from the first session, so this also modifies the `XXX.o` in the previous finalized session directory. * Codegen emits an error b/c `missing` is not an instruction, so we abort before finalizing the incremental session. Specifically, this means that the *previous* session is the last finalized session. Session 3 (`rpass3`): * Load artifacts from the previous *finalized* incremental session, namely the dep graph. NOTE that this is from session 1. * All the dep graph nodes are green since we are basically replaying session 1. * codegen object file `XXX.o`, which is detected as *reused* from session 1 since dep nodes were green. That means we **reuse** `XXX.o` which had been dirtied from session 2. * Link the binary and stuff. This results in a binary which reuses some of the build artifacts from session 2, but thinks it's from session 1. At this point, I hope it's clear to see that the incremental results from session 1 were dirtied from session 2, but we reuse them as if session 1 was the previous (finalized) incremental session we ran. This is at best really buggy, and at worst **unsound**. This isn't limited to `-C save-temps`, since there are other combinations of flags that may keep around temporary files (hard linked) in the working directory (like `-C debuginfo=1 -C split-debuginfo=unpacked` on darwin, for example). --- This PR implements a fix which is to prepend temp filenames with a random string that is generated per invocation of rustc. This string is not *deterministic*, but temporary files are transient anyways, so I don't believe this is a problem. That means that temp files are now something like... `{crate-name}.{cgu}.{invocation_temp}.rcgu.o`, where `{invocation_temp}` is the new temporary string we generate per invocation of rustc. Fixes rust-lang/rust#139407 [^1]: https://github.com/rust-lang/rust/blob/175dcc7773d65c1b1542c351392080f48c05799f/compiler/rustc_fs_util/src/lib.rs#L60 [^2]: https://github.com/rust-lang/rust/blob/175dcc7773d65c1b1542c351392080f48c05799f/compiler/rustc_incremental/src/persist/fs.rs#L1-L40
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Instructions are getting omitted from naked_asm blocks after fixing a compilation error and then rebuilding with
cargo run. Acargo cleanandcargo runis then required to get a correct executable.As a minimal demonstration of this problem this code contains a deliberate error and fails to build:
We fix the source by changing
w1intox1. Which now builds without error but produces the wrong result:Looking at the disassembled executable with
objdump -d target/debug/rust_asm | lesswe find theaddinstruction is missing from theadd_u64()function:Rebuilding with
cargo cleanandcargo runthen produces the correct result:And of course the
addinstruction is now in the executable where we expect it to be:Meta
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