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cmd/go: SIGSEGV in modload.Lookup when testing a file list with -covermode=atomic #81406
Description
go version: reproduces since go1.24, still at tip (1.28-devel_49c3ea64). Works fine on 1.23 and earlier.
Repro (any module root):
go test -covermode=atomic main_test.go go.modExpected (1.23 and earlier):
named files must be .go files: go.mod
Actual:
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0xb8 pc=0x8e8021]
goroutine 1 [running]:
cmd/go/internal/modload.Lookup(...)
cmd/go/internal/modload/load.go:856
cmd/go/internal/load.loadPackageData.func1()
cmd/go/internal/load/pkg.go:905
cmd/internal/par.(*Cache[...]).Do(...)
cmd/internal/par/work.go:160
cmd/go/internal/load.loadPackageData(...)
cmd/go/internal/load/pkg.go:899
cmd/go/internal/load.loadImport(...)
cmd/go/internal/load/pkg.go:736
cmd/go/internal/load.EnsureImport(...)
cmd/go/internal/load/pkg.go:3516
cmd/go/internal/test.runTest(...)
cmd/go/internal/test/test.go:995
Version confirmation:
go1.23.0 test -covermode=atomic main_test.go go.mod
→ named files must be .go files: go.mod (ok)
go1.27.1 test -covermode=atomic main_test.go go.mod
→ SIGSEGV (regression)
Only -covermode=atomic triggers it (set/count/no-cover → clean error).
test.go:995 injects sync/atomic via EnsureImport(moduleLoader, ...) before
named-file validation; in file-list mode the module loader is nil →
nil deref in modload.Lookup (load.go:856).
Found via zsh EXTENDED_GLOB: unquoted -bench ^ expands ^ to the whole cwd
file list (incl. go.mod) — exactly this arg shape.
Activity
thepudds commentedon Sep 9, 2026
Probably not super useful in this case, but FWIW this bisected to 49b3ab0:
gopherbot commentedon Sep 13, 2026
Change https://go.dev/cl/831944 mentions this issue:
cmd/go: avoid panic for invalid file lists with atomic coverage