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io: endless loop in MultiReader in Go 1.7 #16795

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bradfitz opened this issue Aug 19, 2016 · 5 comments
Closed

io: endless loop in MultiReader in Go 1.7 #16795

bradfitz opened this issue Aug 19, 2016 · 5 comments
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Go1.7.1

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@bradfitz
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https://golang.org/cl/17873 (git rev ccdca83, bug #13558) was added in Go 1.7 and introduced a bug where the EOF of a (non-zero, EOF) Read could be ignored and the MultiReader could loop, forever yielding bytes.

Just hit this myself.
@bradfitz bradfitz added this to the Go1.7.1 milestone Aug 19, 2016
@bradfitz bradfitz self-assigned this Aug 19, 2016
@bradfitz
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Sent https://golang.org/cl/27397

@gopherbot
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CL https://golang.org/cl/27397 mentions this issue.

@ianlancetaylor
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The CL says that this bug has been present since Go 1.0, so this is not a 1.7.1 issue.

@ianlancetaylor ianlancetaylor modified the milestones: Go1.8, Go1.7.1 Aug 22, 2016
@bradfitz
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@ianlancetaylor, I think this is bad enough and in a core piece of io to warrant a fix, regardless of how many cycles it's been broken.

Like I said, this bit me in real code and I had to go on a debugging spree to figure out what was going on.

What would people who weren't comfortable debugging the standard library do?

@ianlancetaylor
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Hmmm, well, OK, I guess.

@ianlancetaylor ianlancetaylor modified the milestones: Go1.7.1, Go1.8 Aug 22, 2016
gopherbot pushed a commit that referenced this issue Aug 22, 2016
@bradfitz
io: fix comment in test
e8ba80f 
Updates #16795

Change-Id: I0bcc34bb5a92a2c480aebfb0eb6ba57bcc7f7cfd
Reviewed-on: https://go-review.googlesource.com/27551
Reviewed-by: Ian Lance Taylor <iant@golang.org>
gopherbot pushed a commit that referenced this issue Sep 7, 2016
@bradfitz @broady
[release-branch.go1.7] io: fix infinite loop bug in MultiReader
e464c08 
If an io.Reader returned (non-zero, EOF), MultiReader would yield
bytes forever.

This bug has existed before Go 1 (!!), introduced in the original
MultiReader implementation in https://golang.org/cl/1764043 and also
survived basically the only update to this code since then
(https://golang.org/cl/17873, git rev ccdca83), which was added in
Go 1.7.

This just bit me when writing a test for some unrelated code.

Fixes #16795

Change-Id: I36e6a701269793935d19a47ac12f67b07179fbff
Reviewed-on: https://go-review.googlesource.com/27397
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Reviewed-on: https://go-review.googlesource.com/28633
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
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