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encoding/binary: handle unexported fields more gracefully #19794

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dominikh opened this issue Mar 30, 2017 · 2 comments
Closed

encoding/binary: handle unexported fields more gracefully #19794

dominikh opened this issue Mar 30, 2017 · 2 comments
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Documentation FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Go1.9Maybe

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@dominikh
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What version of Go are you using (go version)?

go version go1.8 linux/amd64

What did you do?

https://play.golang.org/p/gcvrJJD1uS

What did you expect to see?

Either an error to be returned, or the unexported fields to be skipped.

What did you see instead?

panic: reflect: reflect.Value.SetUint using value obtained using unexported field

goroutine 1 [running]:
reflect.flag.mustBeAssignable(0x1a8, 0x0)
	/usr/local/go/src/reflect/value.go:225 +0x1c0
reflect.Value.SetUint(0xf1e00, 0x1040a0d9, 0x1a8, 0x1ce2, 0x78, 0x0)
	/usr/local/go/src/reflect/value.go:1493 +0x40
encoding/binary.(*decoder).value(0x10429f5c, 0xf1e00, 0x1040a0d9, 0x1a8)
	/usr/local/go/src/encoding/binary/binary.go:546 +0xac0
encoding/binary.(*decoder).value(0x10429f5c, 0xf4760, 0x1040a0d9, 0x199)
	/usr/local/go/src/encoding/binary/binary.go:521 +0x320
encoding/binary.Read(0x170630, 0x10440240, 0x1714c0, 0x1931c8, 0xe89a0, 0x1040a0d9, 0x0, 0x2)
	/usr/local/go/src/encoding/binary/binary.go:247 +0x1360
main.main()
	/tmp/sandbox482800808/main.go:16 +0x120
@SamWhited
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SamWhited commented May 10, 2017 •
edited

The documentation for Read says:

When reading into a struct, all non-blank fields must be exported.

That seems to me to indicate that the panic is expected (although that could be made more clear: "~ or Read may panic"). It occurs as far back as Go 1.5, so it does not appear to be a regression.

I've marked this as a Documentation issue for now; if you intended it to be a proposal we can change it.

@SamWhited SamWhited added this to the Go1.9Maybe milestone May 10, 2017
@bradfitz bradfitz added the NeedsFix The path to resolution is known, but the work has not been done. label Jun 28, 2017
@gopherbot
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CL https://golang.org/cl/47093 mentions this issue.

@golang golang locked and limited conversation to collaborators Jun 29, 2018
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Documentation FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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@bradfitz @dominikh @SamWhited @gopherbot