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0branch opened this issue Mar 11, 2015 · 3 comments
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runtime: panic when accessing an empty struct value appended to an uninitialised slice #10135

0branch opened this issue Mar 11, 2015 · 3 comments
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0branch commented Mar 11, 2015

I ran into the following runtime error while attempting access an empty struct value that had been appended to an uninitialised slice: https://play.golang.org/p/J2ItiISh2f,

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0xffffffff addr=0x0 pc=0x202e2]

The append (line 11) succeeds, as does printing the slice as a whole (line 12); accessing the appended struct via range (line 16) yields a panic. Issue encountered under 1.4.1; unable to replicate under gccgo.

Known workaround: comment out line 8 in favour of 9 and make an empty slice explicitly (yuck).

The following also work as expected, though they alter intended behaviour:

  • Modifying the struct to include a single field, allowing for default initialisation
  • Taking a slice of pointers []*empty
@minux minux added this to the Go1.5 milestone Mar 11, 2015
@minux minux changed the title Panic when accessing an empty struct value appended to an uninitialised slice runtime: panic when accessing an empty struct value appended to an uninitialised slice Mar 11, 2015
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minux commented Mar 11, 2015

the problem is that append returns a slice with ptr=nil.
reproducible on tip.

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minux commented Mar 11, 2015

I've sent https://golang.org/cl/7400

@minux minux self-assigned this Mar 11, 2015
@ianlancetaylor ianlancetaylor modified the milestones: Go1.4.3, Go1.5 Mar 11, 2015
@minux minux closed this as completed in 0d6a0d6 Mar 12, 2015
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CL https://golang.org/cl/14248 mentions this issue.

minux added a commit that referenced this issue Sep 22, 2015
@minux @broady
[release-branch.go1.4] runtime: don't return a slice with nil ptr but…
e938de2 
… non-zero len from growslice

Fixes #10135.

Change-Id: Ic4c5ab15bcb7b9c3fcc685a788d3b59c60c26e1e
Signed-off-by: Shenghou Ma <[email protected]>
Reviewed-on: https://go-review.googlesource.com/7400
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-on: https://go-review.googlesource.com/14248
Reviewed-by: Andrew Gerrand <[email protected]>
@ianlancetaylor ianlancetaylor modified the milestone: Go1.4.3 Sep 22, 2015
@bradfitz bradfitz mentioned this issue Mar 7, 2016
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@golang golang locked and limited conversation to collaborators Sep 22, 2016
wheatman pushed a commit to wheatman/go-akaros that referenced this issue Jun 25, 2018
@minux @wheatman
[release-branch.go1.4] runtime: don't return a slice with nil ptr but…
c5d7351 
… non-zero len from growslice

Fixes golang#10135.

Change-Id: Ic4c5ab15bcb7b9c3fcc685a788d3b59c60c26e1e
Signed-off-by: Shenghou Ma <[email protected]>
Reviewed-on: https://go-review.googlesource.com/7400
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-on: https://go-review.googlesource.com/14248
Reviewed-by: Andrew Gerrand <[email protected]>
wheatman pushed a commit to wheatman/go-akaros that referenced this issue Jun 26, 2018
@minux @wheatman
[release-branch.go1.4] runtime: don't return a slice with nil ptr but…
813d3d6 
… non-zero len from growslice

Fixes golang#10135.

Change-Id: Ic4c5ab15bcb7b9c3fcc685a788d3b59c60c26e1e
Signed-off-by: Shenghou Ma <[email protected]>
Reviewed-on: https://go-review.googlesource.com/7400
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-on: https://go-review.googlesource.com/14248
Reviewed-by: Andrew Gerrand <[email protected]>
wheatman pushed a commit to wheatman/go-akaros that referenced this issue Jul 9, 2018
@minux @wheatman
[release-branch.go1.4] runtime: don't return a slice with nil ptr but…
4d5fbe9 
… non-zero len from growslice

Fixes golang#10135.

Change-Id: Ic4c5ab15bcb7b9c3fcc685a788d3b59c60c26e1e
Signed-off-by: Shenghou Ma <[email protected]>
Reviewed-on: https://go-review.googlesource.com/7400
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-on: https://go-review.googlesource.com/14248
Reviewed-by: Andrew Gerrand <[email protected]>
wheatman pushed a commit to wheatman/go-akaros that referenced this issue Jul 20, 2018
@minux @wheatman
[release-branch.go1.4] runtime: don't return a slice with nil ptr but…
f52cdf6 
… non-zero len from growslice

Fixes golang#10135.

Change-Id: Ic4c5ab15bcb7b9c3fcc685a788d3b59c60c26e1e
Signed-off-by: Shenghou Ma <[email protected]>
Reviewed-on: https://go-review.googlesource.com/7400
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-on: https://go-review.googlesource.com/14248
Reviewed-by: Andrew Gerrand <[email protected]>
wheatman pushed a commit to wheatman/go-akaros that referenced this issue Jul 30, 2018
@minux @wheatman
[release-branch.go1.4] runtime: don't return a slice with nil ptr but…
f89f411 
… non-zero len from growslice

Fixes golang#10135.

Change-Id: Ic4c5ab15bcb7b9c3fcc685a788d3b59c60c26e1e
Signed-off-by: Shenghou Ma <[email protected]>
Reviewed-on: https://go-review.googlesource.com/7400
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-on: https://go-review.googlesource.com/14248
Reviewed-by: Andrew Gerrand <[email protected]>
@rsc rsc unassigned minux Jun 23, 2022
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