Re: Screensaver won't run on 10.6 even after porting to 64-bit
Re: Screensaver won't run on 10.6 even after porting to 64-bit
- Subject: Re: Screensaver won't run on 10.6 even after porting to 64-bit
- From: Michael Ash <email@hidden>
- Date: Sun, 11 Oct 2009 22:05:37 -0400
On Sun, Oct 11, 2009 at 4:08 PM, Clark Cox <email@hidden> wrote:
> On Sun, Oct 11, 2009 at 1:06 PM, Ben Haller
> <email@hidden> wrote:
>> On 11-Oct-09, at 3:52 PM, Kyle Sluder wrote:
>>
>>> On Oct 11, 2009, at 12:44 PM, Ben Haller <email@hidden>
>>> wrote:
>>>
>>>> OK, makes sense. My only question: what's the best way to switch at
>>>> compile time based on whether GC is enabled for the build? I.e. what do I
>>>> #if or #ifdef? I could do it based on the arch or the SDK, but if there's a
>>>> flag specifically for GC I'd rather use that...
>>>
>>> The purpose of GC-supported rather than GC-required is that you don't do
>>> this. Rather, you write your code so that it works in either retain-release
>>> or garbage collected environments.
>>
>> Yes, but my code also needs to compile as GC-unsupported against the 10.4
>> SDK, where any GC-specific calls that I might need to make will not compile.
>> Am I missing something?
>
> There aren't any "GC-specific calls" to make.
Every time you assign a value to an instance variable, this passes
through a write barrier, which is a fancy way of saying that the
compiler generates code which calls a garbage collection function to
perform the assignment, rather than performing it directly.
Now, I *think* that 10.4 actually has stub versions of all these calls
which work correctly for the non-GC case which will always be found on
10.4, but it's manifestly not the case that there aren't any
GC-specific calls to make. Any code compiled with GC enabled will be
full of GC-specific calls, it's just that very few of them are
explicit.
Mike
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