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reflect: unsafe.Pointer used unsafely in reflect.Value #6490

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lexprfuncall opened this issue Sep 26, 2013 · 8 comments
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reflect: unsafe.Pointer used unsafely in reflect.Value #6490

lexprfuncall opened this issue Sep 26, 2013 · 8 comments
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Go1.3

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@lexprfuncall
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An unsafe pointer typed value is used as both bytes and a pointer in the val member of a
reflect Value structure.  The code knows how to interpret this value correctly based on
a convention of flags stored elsewhere in the value structure.  In essence the code
treats this field as a variant record though the rest of the toolchain has no knowledge
of this convention.

Since there is no variant record concept in Go, the value storage should not conflate
the types of this location.  One possible solution is to split the field storage into
two fields: a uintptr field for non-pointer values and a unsafe.Pointer field for
pointer values.  The same flags can be used to control which field is loaded.
@rsc
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rsc commented Sep 27, 2013

Comment 1:

Labels changed: added priority-later, go1.3, removed priority-triage.

@rsc
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rsc commented Dec 4, 2013

Comment 2:

Labels changed: added release-go1.3.

@rsc
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rsc commented Dec 4, 2013

Comment 3:

Labels changed: removed go1.3.

@rsc
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rsc commented Dec 4, 2013

Comment 4:

Labels changed: added repo-main.

@bradfitz
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Comment 5:

Is this now entirely fixed by,
https://code.google.com/p/go/source/detail?r=ecccf07e7f
reflect: rewrite Value to separate out pointer vs. nonpointer info.
Needed for precise gc and copying stacks.
reflect.Value now takes 4 words instead of 3.
Still to do:
 - un-iword-ify channel ops.
 - un-iword-ify method receivers.
R=golang-dev, iant, rsc, khr
CC=golang-dev
https://golang.org/cl/43040043
?

Owner changed to @randall77.

Status changed to Started.

@randall77
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Comment 6:

Yes, this bug is mainly fixed by that change.  There are still those pesky still-to-do
notes to make reflect.Value totally gc-clean.

@randall77
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Comment 7:

This issue was updated by revision 2af7a26.

R=rsc
CC=golang-codereviews
https://golang.org/cl/52110044

@randall77
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Comment 8:

This issue was closed by revision 873aaa5.

Status changed to Fixed.

@rsc rsc added this to the Go1.3 milestone Apr 14, 2015
@rsc rsc removed the release-go1.3 label Apr 14, 2015
@golang golang locked and limited conversation to collaborators Jun 25, 2016
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@bradfitz @rsc @lexprfuncall @randall77 @gopherbot