Date: Thu, 11 Mar 2010 23:58:40 -0600 (CST) From: Scott Bennett <bennett@cs.niu.edu> To: freebsd-questions@freebsd.org, Nerius Landys <nlandys@gmail.com> Cc: Alex Stangl <alex@stangl.us> Subject: Re: Objective-C 2.0 on FreeBSD; garbage collection, anyone? Message-ID: <201003120558.o2C5welE022368@mp.cs.niu.edu>
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On Wed, 10 Mar 2010 11:14:25 -0800 Nerius Landys <nlandys@gmail.com>
wrote:
>>> I am compiling this program and running it, and without the "release"
>>> calls there, it certainly is using up more and more memory every
>>> second. Definitely no garbage collection happening. I then modified
>>> the GNUmakefile to make sure that the option "-fobjc-gc" was being
>>> passed to gcc, and verbose output from make assured me that this was
>>> the case. However, my program sill did not garbage collect (3 gigs of
>>> RAM, then a segfault). I then tried the gcc option "-fobjc-gc-only"
>>> and gcc42 reported that it did not recognize that option. The options
>>> are described here:
>>> http://developer.apple.com/mac/library/documentation/DeveloperTools/gcc-4.0.1/gcc/Objective_002dC-and-Objective_002dC_002b_002b-Dialect-Options.html
>>
>> While I am not very familiar with Objective C, I can tell you that GC
>> generally runs in the background, using idle time to scavenge memory.
>> (It's not counted pointers, synchronously freeing memory immediately.)
>> So if you race to allocate memory in an infinite loop like this, you are
>> destined to exhaust memory, GC or no, unless the runtime is designed to
>> force a GC on alloc in low memory conditions.
>>
>> Try putting some sort of sleep in the middle of your loop and see if GC
>> kicks in and you get more of a sawtooth memory usage pattern.
>
>Well thanks for that advice. My new program looks like this:
>
>#import "GarbageObj.h"
>
>int main(int argc, const char *argv[]) {
> int inx = 0;
> while (YES) {
> inx++;
> GarbageObj *obj = [[GarbageObj alloc] init];
> [obj foo];
> if (inx == 100000) {
> inx = 0;
> sleep(1);
> }
> }
> return 0;
>}
>
>
>
>Unfortunately the memory usage is still steadily increasing. No
>garbage collection even if I compile with "-fobjc-gc". :-(
>
If your program never frees any memory, then there is never any
garbage to collect. QED.
Scott Bennett, Comm. ASMELG, CFIAG
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