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Invalid "ignoring emit path because multiple .s files were produced" message #122509

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pacak opened this issue Mar 14, 2024 · 0 comments · Fixed by #122842
Closed

Invalid "ignoring emit path because multiple .s files were produced" message #122509

pacak opened this issue Mar 14, 2024 · 0 comments · Fixed by #122842
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A-diagnostics Area: Messages for errors, warnings, and lints T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@pacak
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pacak commented Mar 14, 2024

Code

#[inline(never)]
pub fn alpha() -> usize {
    println!("alpha");
    12
}

#[inline(never)]
pub fn beta() -> usize {
    println!("beta");
    12
}

Current output

$ rustc lib.rs --crate-type lib --emit asm -C codegen-units=2
warning: ignoring emit path because multiple .s files were produced

warning: 1 warning emitted

Desired output

blank

Rationale and extra context

Error originates from somewhere around here and implies that I passed --emit foo=some_name, while in fact I only passed --emit foo

rust/compiler/rustc_codegen_ssa/src/back/write.rs

Lines 595 to 599 in fe61575

if crate_output.outputs.contains_key(&output_type) {
// 2) Multiple codegen units, with `--emit foo=some_name`. We have
// no good solution for this case, so warn the user.
sess.dcx().emit_warn(errors::IgnoringEmitPath { extension });
} else if crate_output.single_output_file.is_some() {

Other cases

No response

Rust Version

rustc 1.78.0-nightly (1a648b397 2024-02-11)
binary: rustc
commit-hash: 1a648b397dedc98ada3dd3360f6d661ec2436c56
commit-date: 2024-02-11
host: x86_64-unknown-linux-gnu
release: 1.78.0-nightly
LLVM version: 17.0.6

Anything else?

No response
@pacak pacak added A-diagnostics Area: Messages for errors, warnings, and lints T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Mar 14, 2024
@jieyouxu jieyouxu added the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label Mar 15, 2024
This was referenced Mar 21, 2024
Merged
Merged
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Mar 25, 2024
@matthiaskrgr
Rollup merge of rust-lang#122842 - pacak:explicit_name, r=michaelwoer…
ded16b3 
…ister

Don't emit an error about failing to produce a file with a specific name if user never gave an explicit name

Fixes rust-lang#122509

You can ask `rustc` to produce some intermediate results with `--emit foo`, this operation comes in two flavors: `--emit asm` and `--emit asm=foo.s`. First one produces one or more `.s` files without any name guarantees, second one renames it into `foo.s`. Second version only works when compiler produces a single file - for asm files this means using a single compilation unit for example.

In case compilation produced more than a single file `rustc` runs following check to emit some warnings:

```rust
            if crate_output.outputs.contains_key(&output_type) {
                // 2) Multiple codegen units, with `--emit foo=some_name`. We have
                //    no good solution for this case, so warn the user.
                sess.dcx().emit_warn(errors::IgnoringEmitPath { extension });
            } else if crate_output.single_output_file.is_some() {
                // 3) Multiple codegen units, with `-o some_name`. We have
                //    no good solution for this case, so warn the user.
                sess.dcx().emit_warn(errors::IgnoringOutput { extension });
            } else {
                // 4) Multiple codegen units, but no explicit name. We
                //    just leave the `foo.0.x` files in place.
                // (We don't have to do any work in this case.)
            }
```

Comment in the final `else` branch implies that if user didn't ask for a specific name - there's no need to emit warnings. However because of the internal representation of `crate_output.outputs` - this doesn't work as expected: if user asked to produce an asm file without giving it an implicit name it will contain `Some(None)`.

To fix the problem new code actually checks if user gave an explicit name. I think this was an original intentional behavior, at least comments imply that.
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Mar 25, 2024
@rust-timer
Unrolled build for rust-lang#122842
e37bc75 
Rollup merge of rust-lang#122842 - pacak:explicit_name, r=michaelwoerister

Don't emit an error about failing to produce a file with a specific name if user never gave an explicit name

Fixes rust-lang#122509

You can ask `rustc` to produce some intermediate results with `--emit foo`, this operation comes in two flavors: `--emit asm` and `--emit asm=foo.s`. First one produces one or more `.s` files without any name guarantees, second one renames it into `foo.s`. Second version only works when compiler produces a single file - for asm files this means using a single compilation unit for example.

In case compilation produced more than a single file `rustc` runs following check to emit some warnings:

```rust
            if crate_output.outputs.contains_key(&output_type) {
                // 2) Multiple codegen units, with `--emit foo=some_name`. We have
                //    no good solution for this case, so warn the user.
                sess.dcx().emit_warn(errors::IgnoringEmitPath { extension });
            } else if crate_output.single_output_file.is_some() {
                // 3) Multiple codegen units, with `-o some_name`. We have
                //    no good solution for this case, so warn the user.
                sess.dcx().emit_warn(errors::IgnoringOutput { extension });
            } else {
                // 4) Multiple codegen units, but no explicit name. We
                //    just leave the `foo.0.x` files in place.
                // (We don't have to do any work in this case.)
            }
```

Comment in the final `else` branch implies that if user didn't ask for a specific name - there's no need to emit warnings. However because of the internal representation of `crate_output.outputs` - this doesn't work as expected: if user asked to produce an asm file without giving it an implicit name it will contain `Some(None)`.

To fix the problem new code actually checks if user gave an explicit name. I think this was an original intentional behavior, at least comments imply that.
@jieyouxu jieyouxu removed the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label Mar 25, 2024
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