Update locally-built rustc instructions #1610
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I didn't realize miri required a full 2-stage build. Are there other tools that require two stages, maybe clippy? I'd like to have a defaults profile for them, right now there's only 'compiler' and 'user' neither of which are really correct. |
CONTRIBUTING.md
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| # Build a stage 2 rustc. | ||
| # This step can take 30 minutes or more. | ||
| ./x.py build --stage 2 library/std |
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I've just noticed that this doesn't work locally; I get an error like:
error[E0463]: can't find crate for `rustc_attr`
--> src/lib.rs:14:1
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14 | extern crate rustc_attr;
| ^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate
error: aborting due to previous error
For more information about this error, try `rustc --explain E0463`.
error: could not compile `miri`
But ./x.py build --stage 2 compiler/rustc fixes it even though it takes three seconds to execute. Is this an x.py bug?
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Wait, only three seconds to execute? Something really weird is going on here ... Maybe this is something like rust-lang/rust#73519 ?
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Yeah ./x.py build --stage 2 compiler/rustc is right.
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@RalfJung do you know why miri requires the compiler artifacts from the next stage? Is it a compiler plugin instead of being linked to the compiler?
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Is it a compiler plugin instead of being linked to the compiler?
What is the difference between these two?
Miri is linked to the compiler, and of course also linked to the standard library. Thus it needs a librustc and a libstd that were both built by the same rustc as the one building Miri itself. (Only things built by the same compiler can be linked together.) Stage 1 does not satisfy this condition, only stage 2 does.
There is a way to fiddle with all the flags (using different versions of rustc for different things) to not require full boostrapping -- that's why ./x.py test src/tools/miri --stage 0 works. But doing this without bootstrap's help is near impossible.
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./x.py build --stage 1 library/std didn't work:
error[E0463]: can't find crate for `rustc_attr`
--> src/lib.rs:14:1
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14 | extern crate rustc_attr;
| ^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate
error: aborting due to previous error
(And I checked to make sure I set the toolchain to r2stage1 -- all the deps compiled fine, just miri failed.)
The x.py build took 3 mins and 35 seconds, which sounds a little fast to me.
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@jyn514 ./x.py build --stage 1 compiler/rustc worked!
It took 23 minutes, so it must be doing more than build --stage 1 library/std.
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I just looked at the x.py logs and it seems like build --stage 1 library/std builds:
- stage0 std artifacts
- stage0 compiler artifacts
- stage1 std artifacts
But the output is kind of confusing so I'm not 100% sure.
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./x.py build --stage 1 compiler/rustc worked!
What exactly did you test to conclude that Miri works? Did you do ./miri test? I definitely tried this in the past and it did not work, and IIRC proc-macros were the culprit.
EDIT: Ah no I misread, you did build rustc twice.
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Ah no I misread, --stage 1 compiler/rustc builds rustc twice, so it is basically the same as --stage 2 compiler/rustc I think? Just some uplifting is happening.
it seems like build --stage 1 library/std builds:
Yes. And --stage 1 compiler/rustc additionally builds "stage1 compiler artifacts", also known as "the stage 2 compiler".
Which switch did you use after a ./x.py build --stage 1 compiler/rustc, to then build Miri?
CONTRIBUTING.md
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| # If you change something, you can get a faster rebuild by doing | ||
| ./x.py --keep-stage 0 build src/rustc | ||
| ./x.py build --keep-stage 0 --stage 2 library/std |
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Probably will happen for this too.
I think having too many profiles wold be somewhat confusing.^^ Only very few people will need this for Miri I think, and instead of making this easier we should get rust-lang/rust#76666 fixed which will make this mostly unnecessary. |
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📌 Commit 1496462 has been approved by |
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☀️ Test successful - checks-actions |
CONTRIBUTING.md: Use `build --stage 1` instead of `build --stage 2` It seems to work fine with `--stage 1` and it should be faster. Cc #1610 Cc `@jyn514`
Cc rust-lang/rust#78435