Re: [ZEND-ENGINE-CVS] cvs: ZendEngine2(PHP_5_3) / zend.h zend_ptr_stack.h zend_types.h zend_vm_def.h zend_vm_execute.h

> On Wed, 2009-06-03 at 22:11 +0100, Nuno Lopes wrote:
>> >> So I'm not particularly happy this solution. First it relies on gcc: 
>> >> the
>> >> code is still broken for other compilers following C99 strict aliasing
>> >> rules.
>> >> Second you're using may_alias and restrict at the same time, which 
>> >> have
>> >> opposite meanings. They refer to different pointers, but it's still
>> >> confusing.
>> >
>> > may_alias means a particular type can alias any other type (like char
>> > does)
>> > restrict means a particular variable cannot be accessed through other
>> > variables in the current scope/block.
>> >
>> > So I used restrict to cancel the performance effect of may_alias on the
>> > function's code.
>>
>> exactly my point: it's very confusing :)
>> The interplay of two variables with these two attributes is also tricky.
>>
>>
>> >> As these functions are only called from 2 sites, I think fixing the
>> >> function
>> >> signature to the right types is the right solution.
>> >
>> > I agree, however there is some other potential problems that may need 
>> > to
>> > be fixed, and which will not be fixable in this way.
>>
>> like what? I haven't checked the code, but what are the other potential
>> problems?
>>
>>
>> > So this fix is an attempt to do something generic and useable for other
>> > cases. I found this solution not too bad as this is still a pointer 
>> > type
>> > which can be assigned to (as opposed to using a char type), and it is
>> > compatible with the original type.
>> >
>> > As you pointed, may_alias is gcc-specific, but is there other compiler
>> > with this level of strictness without such attribute ?
>>
>> I don't know. I know that at least ICC and suncc have strict aliasing
>> analysis, but I dunno what's their support for these attributes (or if 
>> they
>> will be detected as gcc by the configure script).
>>
>
> You are right, thanks for having reviewed this. I have reverted this to
> something simpler/better.

Thank you!
Nuno