tree 25e0db6a0767c6a0bad3f6f089de581d0779fef3
parent a2250d31f3d7ec4a68647c4e5a3613a3e2ebc2f5
author Matthew Dempsky <mdempsky@google.com> 1597289941 -0700
committer Matthew Dempsky <mdempsky@google.com> 1602874207 +0000

x/tools/go/analysis/passes/unsafeptr: stricter reporting

The unsafe.Pointer safety rules have three separate rules allowing
conversion of uintptr to unsafe.Pointer:

(3) allows converting unsafe.Pointer to uintptr, performing
arithmetic, and converting back;

(5) allows converting the results from calling
reflect.Value.{Pointer,UnsafeAddr} to unsafe.Pointer; and

(6) allows converting the Data field of reflect.{Slice,String}Header
to unsafe.Pointer.

Notably, these are three separate rules, and they're not allowed to be
arbitrarily mixed. For example, this is not allowed:

    unsafe.Pointer(v.UnsafeAddr() + x) // BAD

It needs to instead be written as:

    unsafe.Pointer(uintptr(unsafe.Pointer(v.UnsafeAddr())) + x)

(For further explanation on why this is necessary, see
https://github.com/google/go-cmp/issues/167#issuecomment-546093202.)

This CL brings cmd/vet's unsafeptr check inline with the
unsafe.Pointer rules and cmd/compile's implementation thereof.

Change-Id: I1844e0f71dcc8fb7aafacc144b86cc80a2b83b42
Reviewed-on: https://go-review.googlesource.com/c/tools/+/248191
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>