cmd/compile: invalid pointer found on stack when compiled with -race #63657
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mauri870
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the
NeedsInvestigation
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Seems to only affect 1.21.x, I was unable to reproduce it in 1.20 or tip. Reproduced on both darwin/arm64 and linux/amd64 This message in the stacktrace caught my attention: |
mauri870
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RaceDetector
compiler/runtime
mauri870
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cc @golang/compiler |
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@mauri870 CL https://go.dev/cl/531815 fixes the "unexpected SPWRITE" message. But that is just a message, unrelated to the original bad pointer bug. |
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That sounded like a red herring, thanks for clarifying it. |
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The program starts failing since https://go-review.googlesource.com/c/go/+/270940, then "fixed" after https://go-review.googlesource.com/c/go/+/517775 Kindly cc @randall77 and @mdempsky to decide what should we do. |
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This looks like a bad reordering of a nil pointer check and subsequent pointer arithmetic.
start a write barrier to initialize new object allocated above. Write barrier is done here, now to do the actual write. But first there are some other instructions! These 2 instructions are the actual write. Some uninteresting stuff follows. The nil pointer check of the result of Then we actually read |
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Reminds me of #42673, which is what CL 270940 was supposed to fix, not cause. Somehow the nil check just isn't getting the priority it needs to come before the address calculation Here's a reproducer. At least, you can see the problem in assembly. (It will need a wrapper to make it into a test.) When compiled (no Note the The trick with the |
randall77
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@gopherbot Please open a backport issue for 1.21. |
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Backport issue(s) opened: #63743 (for 1.21). Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://go.dev/wiki/MinorReleases. |
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Change https://go.dev/cl/537775 mentions this issue: |
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Change https://go.dev/cl/538595 mentions this issue: |
Update #63657 Update #45573 Change-Id: I163c6038c13d974dc0ca9f02144472bc05331826 Reviewed-on: https://go-review.googlesource.com/c/go/+/538595 LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Keith Randall <khr@google.com>
dmitshur
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NeedsFix
What version of Go are you using (
go version)?Does this issue reproduce with the latest release?
Yes, as of this writing "go1.21.3".
What operating system and processor architecture are you using (
go env)?go envOutputWhat did you do?
Run
go test -race .in this go module.I couldn't reproduce it without dependencies, but the code is quiet small. I'm only "using" Ginkgo and Gomega. Of another dependency I'm just using a type which only ever set to
nil. I've added some comments.The error only occurs in Go 1.21. Go 1.20 works fine. Also the
-raceflag is required.When I remove dead code the panic doesn't occur.
What did you expect to see?
Ginkgo test results.
What did you see instead?
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