CODEWITHSUNDEEP
go
mattdm
mattdm

Reputation: 2291

How do I get object build info out of a Go library?

I'm trying to build a Go program where I have a required library on my system in binary form. However, go build fails with

object is [linux amd64 go1.1.1 X:none] expected [linux amd64 go1.1.2 X:none]

I see what the immediate problem is: the static library was built with an older version of Go. How can I read that information from the .a file directly? (I can see it with strings library.a | grep '^go object', but is there something that's meant to output the build string? (And, what is that string properly called?)

Upvotes: 1

Views: 622

Answers (1)

James Henstridge
James Henstridge

Reputation: 43899

The .a files the Go compiler produces are managed using the pack tool. The metadata used to link the package is found in the __.PKGDEF member of the archive.

You can extract this file from an archive to stdout with:

go tool pack p path/to/package.a __.PKGDEF

It starts with the build signature you're after, so you could either take the first line or grep for ^go object as you were with the output of strings (this should be a bit more reliable, in case that text shows up as a constant in the program code).

Upvotes: 1

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