Spec does not explain comparing pointers to zero-sized objects

[ianlancetaylor]

As far as I can see, the spec does not let me predict the result of this program.  The
spec doesn't say anything clearly about comparing two pointers to zero-sized objects.

Both 6g and gccgo current print "true", so I would vote for formalizing that.

package main

type S struct { }
type A [10]S

func main() {
    var a A
    p1 := &a[0]
    p2 := &a[1]
    if p1 == p2 {
        println("true")
    } else {
        println("false")
    }
}

[ianlancetaylor]

Comment 1:

Owner changed to @griesemer.

[rsc]

Comment 2:

The spec should make clear that while it is permissible
for pointers to distinct 0-sized objects to compare equal,
it is also permissible for them to compare unequal.
No guarantee is made.
For example,
x := make([]struct{}, 10)
y := make([]struct{}, 10)
&x[0] == &y[1]?  Maybe.
Russ

[griesemer]

Comment 3:

This issue was closed by revision 1320ce0.

Status changed to Fixed.