new, delete, Objective-C++, and leaks

Question

I'm adding functionality to an existing Cocoa application written mostly in Objective-C. I have to use an existing c++ class in the class I'm writing, so the new class is Objective-C++. Furthermore, I've had to write a method on the c++ class that temporarily uses a buffer. So my c++ method is something like

(void) myMethod{
   int8_t* bffr = new int8_t[length];
   // use the buffer
   delete [] bffr;
}

I instantiate the c++ class in my .mm file, and try to carry on. The problem is that the application crashes. However, if I comment out the delete, the app does not crash, but Instruments reports a leak associated with this method. I presume that the Objective-C memory management is getting bolluxed up. How can I resolve this catch-22?

BTW, I get the same result using malloc and get_temporary_buffer.

It's quite possible there is an issue with your 'use the buffer' code, please show us what it does. — Joshua Weinberg
– Joshua Weinberg, Commented Dec 9, 2011 at 15:04
+1 @JoshuaWeinberg if your buffer is affected to a non-copied ObjectiveC object, it can't be safely deleted. — jv42
– jv42, Commented Dec 9, 2011 at 15:06

勿绮语 · Accepted Answer · 2012-04-19 03:54:14Z

1

You must free the memory you allocated and do so at the right time - only after the time that no other code will ever attempt to access that piece of memory.

edited Apr 19, 2012 at 3:54

answered Dec 9, 2011 at 15:08

勿绮语

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1 Comment

garyp Over a year ago

Argh. I've looked at that use the buffer code for a couple of hours and thanks to this reply I notice that I've overwritten bffr. Fixed. Thanks.

Jay · Accepted Answer · 2011-12-09 15:15:08Z

0

Have you tried enabling the memory debugging features in Xcode to track down the source of the crash?

(Edit Scheme > Debug > Memory Mgmt, tick all boxes)

Cheers, Jay

answered Dec 9, 2011 at 15:15

Jay

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