golang/go

cmd/go: make cache keys for libraries in GOROOT insensitive to `-trimpath`

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#57,346 opened on Dec 15, 2022

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Description

In CL 380915 we observed that libraries in GOROOT contain the literal string $GOROOT instead of their absolute paths, even when -trimpath is not set.

As a result, we should (theoretically) compile the same bytes for those libraries regardless of whether -trimpath is set. We can therefore omit -trimpath from the cache key, allowing object files already in the cache to be reused in more cases.

We should add a script test that verifies that the library object files really don't depend on the -trimpath flag, make the flags passed to the compiler ignore cfg.BuildTrimpath for those libraries, and then update cmd/go/internal/work to omit it from the cache key.

(Note that we cannot omit it from the cache key for executables, since those are stamped with the actual GOROOT or GOROOT_FINAL during linking.)

Contributor guide

Research direction
Examine the cache key logic in cmd/go/internal/work and create a script test to verify that trimpath does not affect library object files.
Tech stack
go
Domain
backend
Issue type
Refactor
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
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Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GoGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65