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cmd/link: ABI hash for package in shared library should not include package's buildID #19920

mwhudson opened this issue Apr 11, 2017 · 1 comment


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@mwhudson mwhudson commented Apr 11, 2017

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

1.7 (but nothing has changed here lately)

What operating system and processor architecture are you using (go env)?


What did you do?

Applied a distro patch that does not change the exported API of any package, but does add a new file (it adds a header file to runtime/cgo, to be precise)

What did you expect to see?

I expected the ABI hash of to be the same.

What did you see instead?

It had changed.

This turns out to be because the linker computes the ABI hash for the shared library by hashing the __.PKGDEF file from each .a file going into the shared library. But that includes the build id that the go tool determines, which is irrelevant for this purpose. I think it would be better to just hash the first line of __.PKGDEF (which has the version of the compiler and GOEXPERIMENT markers) and then the export data, which after all is what the compiler looks at when compiling code that imports this package (which can be found by looking for $$ markers, I think).

Practice suggests that this might still be too fine -- I need to think about preventing inlining across module boundaries -- but that's mostly orthogonal, I think.

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@gopherbot gopherbot commented Apr 12, 2017

CL mentions this issue.

@gopherbot gopherbot closed this in 533ed96 Apr 17, 2017
@golang golang locked and limited conversation to collaborators Apr 17, 2018
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