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mdempsky cmd/compile: add -d=checkptr to validate unsafe.Pointer rules
This CL adds -d=checkptr as a compile-time option for adding
instrumentation to check that Go code is following unsafe.Pointer
safety rules dynamically. In particular, it currently checks two

1. When converting unsafe.Pointer to *T, make sure the resulting
pointer is aligned appropriately for T.

2. When performing pointer arithmetic, if the result points to a Go
heap object, make sure we can find an unsafe.Pointer-typed operand
that pointed into the same object.

These checks are currently disabled for the runtime, and can also be
disabled through a new //go:nocheckptr annotation. The latter is
necessary for functions like strings.noescape, which intentionally
violate safety rules to workaround escape analysis limitations.

Fixes #22218.

Change-Id: If5a51273881d93048f74bcff10a3275c9c91da6a
Run-TryBot: Matthew Dempsky <>
TryBot-Result: Gobot Gobot <>
Reviewed-by: Keith Randall <>
Latest commit 80a6fed Feb 12, 2019

The Go Programming Language

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