DMD optimization bug?

[Iain Buclaw]

On 21 March 2013 21:46, Iain Buclaw <ibuclaw at ubuntu.com> wrote:

>
> On 21 March 2013 20:29, Jacob Carlborg <doob at me.com> wrote:
>
>> The code below works fine without optimizations. But with optimizations
>> (the -O flag) turned on it segfaults. The behavior with optimizations
>> turned on is a bit different depending on which version of DMD I try and if
>> I compile for 32 or 64bit.
>>
>> DMD 2.062 64bit: Segfault
>> DMD 2.062 32bit: Prints a huge array then segfault
>> DMD 2.061 64bit: Segfault
>> DMD 2.061 32bit: Prints a fairly small array (10 elements) with random
>> numbers
>> DMD head (7dcc72a997) 32bit: Bus error: 10
>>
>> I'm using Mac OS X 10.8.2.
>>
>> import std.stdio;
>>
>> int[]* getDeserializedSlice ()
>> {
>>     void[] a = [1, 2, 3, 4, 5].dup;
>>     auto b = &a;
>>
>>     if (auto c = b)
>>         auto d = &(cast(int[]) *c)[1 .. 1 + 2];
>>
>>     return null;
>> }
>>
>> void main ()
>> {
>>     writeln(*getDeserializedSlice());
>> }
>>>
>>>
>>
>> Is the above code supposed to work? The test case might look a bit
>> strange, the full source code is here:
>>
>>
>> https://github.com/jacob-carlborg/orange/blob/master/orange/serialization/Serializer.d#L1672
>>
>> --
>> /Jacob Carlborg
>>
>
>
> As I see it, that code should *always* cause a segmentation fault.
>
> You are returning 'null', and then dereferencing it...
>
>
Just to be clear, the program should stop at the point of:

writeln(*getDeserializedSlice())

Where getSerializedSlice() has returned 'null' and then null gets
dereferenced.  All other behaviours where the program tries to print
*(null) are wrong code.


-- 
Iain Buclaw

*(p < e ? p++ : p) = (c & 0x0f) + '0';
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