code review 121890043: go.blog/context: don't use the address of an empty stru...

go.blog/context: don't use the address of an empty struct as a context
key, as this is not guaranteed to be unique.

Fixes issue 8443.

[Sameer Ajmani, 2014-07-30 02:02:23]

Hello adg (cc: campoy, golang-codereviews@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go.blog

[campoy, 2014-07-30 02:16:41]

https://codereview.appspot.com/121890043/diff/40001/content/context/userip/us...
File content/context/userip/userip.go (right):

https://codereview.appspot.com/121890043/diff/40001/content/context/userip/us...
content/context/userip/userip.go:27: const userIPKey key = 0
Why zero? Will this conflict with the default value of the key?
I know the answer, but Is it worth explaining it?

[Sameer Ajmani, 2014-07-30 02:20:23]

https://codereview.appspot.com/121890043/diff/40001/content/context/userip/us...
File content/context/userip/userip.go (right):

https://codereview.appspot.com/121890043/diff/40001/content/context/userip/us...
content/context/userip/userip.go:27: const userIPKey key = 0
On 2014/07/30 02:16:40, campoy wrote:
> Why zero? Will this conflict with the default value of the key?
> I know the answer, but Is it worth explaining it?

No, it's just an integer value.  Additional keys of type key in this package
would have different integer values.  I think this is fine.

[campoy, 2014-07-30 02:22:15]

On 2014/07/30 02:20:23, Sameer Ajmani wrote:
>
https://codereview.appspot.com/121890043/diff/40001/content/context/userip/us...
> File content/context/userip/userip.go (right):
> 
>
https://codereview.appspot.com/121890043/diff/40001/content/context/userip/us...
> content/context/userip/userip.go:27: const userIPKey key = 0
> On 2014/07/30 02:16:40, campoy wrote:
> > Why zero? Will this conflict with the default value of the key?
> > I know the answer, but Is it worth explaining it?
> 
> No, it's just an integer value.  Additional keys of type key in this package
> would have different integer values.  I think this is fine.

LGTM

I'd still prefer to have some comment on the code specifying that:

// Additional keys of type key in this package would have different integer
values.

[Sameer Ajmani, 2014-07-30 02:29:38]

On 2014/07/30 02:22:15, campoy wrote:
> On 2014/07/30 02:20:23, Sameer Ajmani wrote:
> >
>
https://codereview.appspot.com/121890043/diff/40001/content/context/userip/us...
> > File content/context/userip/userip.go (right):
> > 
> >
>
https://codereview.appspot.com/121890043/diff/40001/content/context/userip/us...
> > content/context/userip/userip.go:27: const userIPKey key = 0
> > On 2014/07/30 02:16:40, campoy wrote:
> > > Why zero? Will this conflict with the default value of the key?
> > > I know the answer, but Is it worth explaining it?
> > 
> > No, it's just an integer value.  Additional keys of type key in this package
> > would have different integer values.  I think this is fine.
> 
> LGTM
> 
> I'd still prefer to have some comment on the code specifying that:
> 
> // Additional keys of type key in this package would have different integer
> values.

Done.

[Sameer Ajmani, 2014-07-30 02:32:15]

*** Submitted as
https://code.google.com/p/go/source/detail?r=76236c79916a&repo=blog ***

go.blog/context: don't use the address of an empty struct as a context
key, as this is not guaranteed to be unique.

Fixes issue 8443.

LGTM=campoy
R=adg, campoy
CC=dsymonds, golang-codereviews
https://codereview.appspot.com/121890043