dnspies:

> Oh so the problem isn't that that ISN'T the default hash used ...
> everything" which is the opposite of true.

You can post an elaboration of this in the main D newsgroup.

Bye,
bearophile

On Thursday, 3 April 2014 at 23:01:27 UTC, Steven Schveighoffer wrote:
> On Thu, 03 Apr 2014 17:42:16 -0400, bearophile <bearophileHUGS@lycos.com> wrote:
>
>
>> I have filed this big problem four years ago or more.
>
> Bug report?
>
> -Steve

This is the closest I could find:

https://d.puremagic.com/issues/show_bug.cgi?id=11025

Here's a couple other related bugs:

https://d.puremagic.com/issues/show_bug.cgi?id=12516

https://d.puremagic.com/issues/show_bug.cgi?id=10374

https://d.puremagic.com/issues/show_bug.cgi?id=1926

On Fri, Apr 04, 2014 at 04:48:52PM +0000, dnspies wrote:
> On Thursday, 3 April 2014 at 23:01:27 UTC, Steven Schveighoffer wrote:
> >On Thu, 03 Apr 2014 17:42:16 -0400, bearophile <bearophileHUGS@lycos.com> wrote:
> >
> >
> >>I have filed this big problem four years ago or more.
> >
> >Bug report?
> >
> >-Steve
> 
> This is the closest I could find:
> 
> https://d.puremagic.com/issues/show_bug.cgi?id=11025
> 
> Here's a couple other related bugs:
> 
> https://d.puremagic.com/issues/show_bug.cgi?id=12516
> 
> https://d.puremagic.com/issues/show_bug.cgi?id=10374
> 
> https://d.puremagic.com/issues/show_bug.cgi?id=1926

I just found this related issue:

	import std.stdio;

	struct MyKey {
		int a;
		char[] b;
	}

	void main() {
		auto key1 = MyKey(1, "abc".dup);
		writefln("key1 hash = %x", typeid(typeof(key1)).getHash(&key1));

		char[] sneaky = "def".dup;
		key1.b[] = sneaky[]; // N.B.: change array contents, keep same pointer

		writefln("key1 hash = %x", typeid(typeof(key1)).getHash(&key1));
	}

Output:

	key1 hash = 6cba62173367a870
	key1 hash = 6cba62173367a870

This means that the hash of MyKey is computed based on its binary representation, disregarding the contents of any array (and other reference) fields. This will certainly break AA's.

I'm almost certain this has already been reported as a bug, but I vaguely remember someone mentioning a while back that this is supposed to have been fixed. But I still get the above problem in DMD git HEAD. :-(


T

-- 
GEEK = Gatherer of Extremely Enlightening Knowledge

H. S. Teoh:

> This means that the hash of MyKey is computed based on its binary
> representation, disregarding the contents of any array (and other
> reference) fields. This will certainly break AA's.
>
> I'm almost certain this has already been reported as a bug, but I
> vaguely remember someone mentioning a while back that this is supposed
> to have been fixed. But I still get the above problem in DMD git HEAD.
> :-(

It needs to be fixed. (Or the code should not compile).

Bye,
bearophile