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spec: clarify that any unsafe.Pointer type is okay in conversion

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The spec is not clear about whether this is allowed or not,
but both compilers allow it, because the reflect implementation
takes advantage of it. Document current behavior.

Fixes #4679.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/7303064
This commit is contained in:
Russ Cox 2013-02-09 17:36:31 -05:00
parent 6ce3e99af0
commit 81eb930f7e
1 changed files with 11 additions and 2 deletions
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13
doc/go_spec.html
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@ -5610,9 +5610,18 @@ func Sizeof(variable ArbitraryType) uintptr
</pre>
<p>
Any pointer or value of <a href="#Types">underlying type</a> <code>uintptr</code> can be converted into
a <code>Pointer</code> and vice versa.
Any pointer or value of <a href="#Types">underlying type</a> <code>uintptr</code> can be converted to
a <code>Pointer</code> type and vice versa.
</p>
<pre>
var f float64
bits = *(*uint64)(unsafe.Pointer(&amp;f))
type ptr unsafe.Pointer
bits = *(*uint64)(ptr(&amp;f))
</pre>
<p>
The functions <code>Alignof</code> and <code>Sizeof</code> take an expression <code>x</code>
of any type and return the alignment or size, respectively, of a hypothetical variable <code>v</code>