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cmd/compile: recognize (*[Big]T)(ptr)[:n:m] pattern for -d=checkptr

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A common idiom for turning an unsafe.Pointer into a slice is to write:

    s := (*[Big]T)(ptr)[:n:m]

This technically violates Go's unsafe pointer rules (rule #1 says T2
can't be bigger than T1), but it's fairly common and not too difficult
to recognize, so might as well allow it for now so we can make
progress on #34972.

This should be revisited if #19367 is accepted.

Updates #22218.
Updates #34972.

Change-Id: Id824e2461904e770910b6e728b4234041d2cc8bc
Reviewed-on: https://go-review.googlesource.com/c/go/+/201839
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Matthew Dempsky 2019-10-17 14:29:16 -07:00
parent dba19c65a7
commit 7b58581a23
4 changed files with 41 additions and 13 deletions
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2
src/cmd/compile/internal/gc/builtin/runtime.go
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@ -235,7 +235,7 @@ func racewriterange(addr, size uintptr)
func msanread(addr, size uintptr)
func msanwrite(addr, size uintptr)
func checkptrAlignment(unsafe.Pointer, *byte)
func checkptrAlignment(unsafe.Pointer, *byte, uintptr)
func checkptrArithmetic(unsafe.Pointer, []unsafe.Pointer)
// architecture variants