syscall: checkptr failures relating to Dirent on darwin and freebsd

[mdempsky]

The freebsd and darwin -race builders are currently failing:

• darwin
• freebsd

Both of these appear to be failing due to use of syscall.Dirent.

[cuonglm]

It does not happen for me under 10.15:

$ env -u GO111MODULE go tool dist test -race go_test:syscall
##### Testing packages.
ok  	syscall	3.549s

ALL TESTS PASSED (some were excluded)

[cuonglm]

It seems that:

$ cd syscall
$ go test -race

trigger the error.

[cuonglm]

So it's not -race, but in #34972, we check with -short, so not all tests were run. With:

go test -a -gcflags=all=-d=checkptr syscall

The test is always false.

[tklauser]

Same happens in golang.org/x/sys/unix on the freebsd-amd64-race builder with -d=checkptr enabled:

https://build.golang.org/log/79e02a85654067a443293a96844a33710e123c27

[mdempsky]

I'm probably not going to have time to look into this for another week or so. If someone wants to fix this, please go for it. Otherwise, it's probably worth at least adding some //go:nocheckptr directives with TODOs referencing this issue to at least get the build passing again.

[cuonglm]

@mdempsky I'm investigating darwin one. Still not clearly understand the issue. If I add runtime.KeepAlive(buf) after this line:

go/src/syscall/getdirentries_test.go

Line 58 in 758eb02

var buf [2048]byte

Then the test pass. But it does fails again with -d=checkptr=2.

[gopherbot]

Change https://golang.org/cl/203077 mentions this issue: syscall: make TestGetdirentries checkptr safe

[gopherbot]

Change https://golang.org/cl/202878 mentions this issue: syscall: make convertFromDirents11 checkptr safe

[gopherbot]

Change https://golang.org/cl/202959 mentions this issue: unix: make convertFromDirents11 checkptr safe