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encoding/binary: inconsistency between Write and Read #22772

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ghost opened this issue Nov 17, 2017 · 2 comments
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encoding/binary: inconsistency between Write and Read #22772

ghost opened this issue Nov 17, 2017 · 2 comments
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FrozenDueToAge Proposal v2 A language change or incompatible library change
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Unplanned

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@ghost
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ghost commented Nov 17, 2017

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

1.9.2

What did you do?

https://play.golang.org/p/aa0RIwHB_2

What did you expect to see?

If Write can encode the struct, Read can decode it.

What did you see instead?

Read panics:

reflect.Value.SetUint using value obtained using unexported field

Probably #Go2, unless there's a way to make Read decode structs with unexported fields.
@bradfitz bradfitz added the v2 A language change or incompatible library change label Nov 17, 2017
@bradfitz bradfitz added this to the Unplanned milestone Nov 17, 2017
@ianlancetaylor
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In general the reflect package permits you to do exactly the operations that the language permits you to do. However, the reflect package is given special dispensation to read unexported fields, even though they can not be read in the language, because otherwise it would be impossible to implement the fmt package. That is what you are observing. If we think that consistency of Read and Write in the encoding/binary package is important, then the fix is going to be to change Write to reject unexported fields.

@ianlancetaylor
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We aren't going to change anything here. Closing as unfortunate.

@golang golang locked and limited conversation to collaborators Mar 27, 2019
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@bradfitz @FiloSottile @ianlancetaylor @gopherbot