check host's libstdc++ version when using ci llvm #125411

onur-ozkan · 2024-05-22T16:41:09Z

If the host's libstdc++ version is too old using ci-llvm may result in an ABI mismatch between the local libstdc++ and libLLVM.so. This PR adds a sanity check to immediately fail at the beginning of the bootstrap before starting the actual build. I am not sure if '8' is the best threshold, but it should be a good start and we can increase it anytime if needed.

Fixes #123037

rustbot · 2024-05-22T16:41:18Z

r? @albertlarsan68

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onur-ozkan · 2024-05-22T16:42:32Z

r? Mark-Simulacrum

src/bootstrap/ci-llvm-libstdcpp-version-threshold

nikic · 2024-05-22T16:48:05Z

src/bootstrap/src/core/sanity.rs

+    if !build.config.dry_run() && build.config.llvm_from_ci {
+        let cxx = build.cxx(build.build).unwrap();
+        let mut cxx_cmd = Command::new(cxx);
+        cxx_cmd.arg("-dumpversion");


Isn't this checking the compiler version rather than libstdcxx version? These are fairly likely to be the same if the compiler is gcc, but not otherwise.

I thought it was the case for any c++ compiler

rust/src/bootstrap/src/core/sanity.rs

Line 112 in 1c38c46

// In case the user has a custom setup that includes a recent libstdc++ with an old c++ compiler, this information might be useful to them.

I have to check if there is a better way.

The compiler and the used C++ standard library are independent. gcc will usually use libstdc++ of the same version (but isn't required). clang on Linux will usually use some libstdc++ version -- in this case the compiler version and libstdc++ version have no relation at all. clang on other platforms like macos will use libc++, in which case the clang version and libc++ version will likely match. Of course, libstdc++ and libc++ are ABI incompatible as well :)

(Not sure whether our apple builders link against libstdc++ or libc++.)

~~Should we check libc++ version too? If so, what would be a good threshold for it?~~

I suppose we don't need to check for it. ABI mismatch only occurs when using download-ci-llvm and ci llvm is built from our builders which use libstdc++.

rustbot · 2024-05-23T09:06:08Z

triagebot.toml has been modified, there may have been changes to the review queue.

cc @davidtwco, @wesleywiser

src/bootstrap/src/core/sanity.rs

onur-ozkan · 2024-05-23T09:11:44Z

@rustbot ready

Mark-Simulacrum · 2024-05-25T22:23:51Z

src/bootstrap/src/core/sanity.rs

@@ -35,6 +36,10 @@ const STAGE0_MISSING_TARGETS: &[&str] = &[
    // just a dummy comment so the list doesn't get onelined
 ];

+/// Minimum version threshold for libstdc++ required when using prebuilt LLVM
+/// from CI (with`llvm.download-ci-llvm` option).
+const LIBSTDCXX_MIN_VERSION_THRESHOLD: usize = 8;


Is minimum really the right thing here? I'd expect that we need an exact match?

Unless there is a breaking change, different versions can be compatible (just like libc). It doesn't need to be the same version.

Mark-Simulacrum · 2024-05-27T20:53:17Z

I suspect we'll hit problems and need to revert & re-land with fixes, just based on something being off (e.g., cxx invocation needing more flags or similar) but this seems OK to start with.

@bors r+

bors · 2024-05-27T20:53:19Z

📌 Commit 480670e has been approved by Mark-Simulacrum

It is now in the queue for this repository.

bors · 2024-06-06T12:52:10Z

⌛ Testing commit dd99021 with merge 50297bb...

bors · 2024-06-06T15:17:25Z

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 50297bb to master...

rust-timer · 2024-06-06T16:22:44Z

Finished benchmarking commit (50297bb): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Warning ⚠: The following benchmark(s) failed to build:

rustc

cc @rust-lang/wg-compiler-performance

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.3%	[0.3%, 0.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary -3.1%, secondary -4.3%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-3.1%	[-3.1%, -3.1%]	1
Improvements ✅ (secondary)	-4.3%	[-4.3%, -4.3%]	1
All ❌✅ (primary)	-3.1%	[-3.1%, -3.1%]	1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

Results (secondary -0.0%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	1
All ❌✅ (primary)	-	-	0

Bootstrap: missing data
Artifact size: 319.39 MiB -> 319.43 MiB (0.01%)

lqd · 2024-06-06T16:29:10Z

Hum, benchmarking bootstrapping broke 👀

onur-ozkan · 2024-06-06T16:43:41Z

Interesting.. Is there a way to check build logs of benchmark runner?

Kobzol · 2024-06-06T16:44:50Z

https://perf.rust-lang.org/status.html click on Show 1 error on the right.

onur-ozkan · 2024-06-06T16:53:06Z

Your system's libstdc++ version is too old for the llvm.download-ci-llvm option.
Current version detected: '7'
Minimum required version: '8'
Consider upgrading libstdc++ or disabling the llvm.download-ci-llvm option.
Building bootstrap
Build completed unsuccessfully in 0:00:16

The runner is using libstdc++ version 7 which is old. Can we use more recent version? The main reason for setting version 8 as the minimum threshold is that version 7 is not compatible with >=8 (see #110472).

lqd · 2024-06-06T17:05:47Z

cc @Mark-Simulacrum on that

petrochenkov · 2024-06-06T17:08:47Z

src/bootstrap/src/core/build_steps/tool.rs

+        let compiler = builder.cxx(self.target).unwrap();
+        let mut cmd = Command::new(compiler);
+
+        let executable = out_dir.join("libcxx-version");


@onur-ozkan

Suggested change

let executable = out_dir.join("libcxx-version");

let executable = out_dir.join("libcxx-version.exe");

How did it pass CI on Windows?
It trivially fails for me locally, because there's no libcxx-version, only libcxx-version.exe.

#126086 should handle this.

Maybe it passed because windows-gnu CI uses env that disables llvm download?

Maybe it passed because windows-gnu CI uses env that disables llvm download?

Yeah, most likely.

use windows compatible executable name for libcxx-version Resolves #rust-lang#125411 (comment)

Rollup merge of rust-lang#126086 - onur-ozkan:use-exe, r=petrochenkov use windows compatible executable name for libcxx-version Resolves #rust-lang#125411 (comment)

Kobzol · 2024-06-08T11:51:03Z

On the perf collector, we have GCC 7.5, which has libstdcxx release 7, sadly. I would suggest that we revert this PR if we don't find a way to update the GCC on the collector quickly (I'm not sure if updating the GCC there wouldn't cause some side effects).

Btw, I think that we should be setting LIBSTDCXX_MIN_VERSION_THRESHOLD according to what is actually used on our CI, not just an arbitrarily selected number. On the x64 builder, we currently use GCC 9.5.0, which returns 9 for _GLIBCXX_RELEASE.

onur-ozkan · 2024-06-08T11:58:18Z

It's not arbitrarily selected number, see #110472 (comment).

Kobzol · 2024-06-08T12:03:18Z

Right, but the fact that 8 works in this case isn't a general fix. If the .so file is built with 9, shouldn't the minimum also be 9? Maybe for libLLVM.so specifically in this case 8 is indeed enough for everyone, but it seems difficult to find the correct version, in general (e.g. once we update GCC on CI sometime in the future).

onur-ozkan · 2024-06-08T12:09:59Z

Setting the threshold to match the version we use in the CI builder would be a solid fix, but it may limit the number of people who can utilize CI LLVM. AFAIK, previous libstdcxx versions can be compatible unless they are excessively outdated.

onur-ozkan · 2024-06-08T12:14:36Z

it may limit the number of people who can utilize CI LLVM

The trade-off here is either ensuring that the threshold version is always correct (by ensuring it matches with the libstdcxx version in CI LLVM builder using some script) or manually finding and updating the version in the bootstrap. Your suggestion seems much more reliable here.

nikic · 2024-06-08T13:30:50Z

The specific problem with libstdc++ 7 here is that it did not yet have a stable C++ 17 ABI. It is generally not necessary to match the libstdc++ version used to build libLLVM.so exactly (the worst that can usually happen is undefined symbol errors, and I think even that isn't possible because we're linking libstdc++ statically).

The C++ 17 ABI is only officially stable since libstdc++ 9, but in practice the ABI of types currently used by the libLLVM <-> rustc_llvm interface didn't change between 8 -> 9 either, which is why it works as a minimum version.

…ck, r=<try> Remove libstdc++ version check error This keeps the error message from rust-lang#125411, but removes the `exit(1)` call. This PR is mostly a hotfix to unblock bootstrap benchmarks in rustc-perf. However, I think that it might be better to just print a warning, in general. If the ABI version does not match, the build might or might not work locally (as we can see on rustc-perf, where it works even if the reported ABI is 7). If it does not work (and **if** we can always recognize this during the LLVM wrapper build, instead of having some silent miscompilations), then the user will have to update their libstdc++ anyway, the error does not help them out on its own. So it should be enough to just provide a better error message, without blocking the build. But I'm not adamant on that, I just want to unblock bootstrap benchmarks until we can find a way to update libstdc++ on the collector machine. CC `@onur-ozkan` r? `@Mark-Simulacrum`

…ck, r=Mark-Simulacrum Remove libstdc++ version check error This keeps the error message from rust-lang#125411, but removes the `exit(1)` call. This PR is mostly a hotfix to unblock bootstrap benchmarks in rustc-perf. However, I think that it might be better to just print a warning, in general. If the ABI version does not match, the build might or might not work locally (as we can see on rustc-perf, where it works even if the reported ABI is 7). If it does not work (and **if** we can always recognize this during the LLVM wrapper build, instead of having some silent miscompilations), then the user will have to update their libstdc++ anyway, the error does not help them out on its own. So it should be enough to just provide a better error message, without blocking the build. But I'm not adamant on that, I just want to unblock bootstrap benchmarks until we can find a way to update libstdc++ on the collector machine. CC `@onur-ozkan` r? `@Mark-Simulacrum`

…k-Simulacrum Remove libstdc++ version check error This keeps the error message from rust-lang/rust#125411, but removes the `exit(1)` call. This PR is mostly a hotfix to unblock bootstrap benchmarks in rustc-perf. However, I think that it might be better to just print a warning, in general. If the ABI version does not match, the build might or might not work locally (as we can see on rustc-perf, where it works even if the reported ABI is 7). If it does not work (and **if** we can always recognize this during the LLVM wrapper build, instead of having some silent miscompilations), then the user will have to update their libstdc++ anyway, the error does not help them out on its own. So it should be enough to just provide a better error message, without blocking the build. But I'm not adamant on that, I just want to unblock bootstrap benchmarks until we can find a way to update libstdc++ on the collector machine. CC `@onur-ozkan` r? `@Mark-Simulacrum`

rustbot assigned albertlarsan68 May 22, 2024

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) labels May 22, 2024

onur-ozkan mentioned this pull request May 22, 2024

Invalid bitcast error when building rustc (rustc-std-workspace-core) #110472

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rustbot assigned Mark-Simulacrum and unassigned albertlarsan68 May 22, 2024

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onur-ozkan force-pushed the sanity-check-libstdc++ branch 2 times, most recently from f2d2bc4 to 1c38c46 Compare May 22, 2024 16:45

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onur-ozkan force-pushed the sanity-check-libstdc++ branch 3 times, most recently from 4c06ca3 to c5755fa Compare May 23, 2024 09:02

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prefer compile::stream_cargo for building tools #125781

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use windows compatible executable name for libcxx-version #126086

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Rollup merge of rust-lang#126086 - onur-ozkan:use-exe, r=petrochenkov

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use windows compatible executable name for libcxx-version Resolves #rust-lang#125411 (comment)

Kobzol mentioned this pull request Jun 9, 2024

Remove libstdc++ version check error #126206

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Optimize libcxx-version for faster bootstrap startups #126467

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check host's libstdc++ version when using ci llvm #125411

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	let executable = out_dir.join("libcxx-version");
	let executable = out_dir.join("libcxx-version.exe");

check host's libstdc++ version when using ci llvm #125411

check host's libstdc++ version when using ci llvm #125411

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Overall result: ❌ regressions - no action needed

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