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I was reading a really large file into memory on the main thread (not just the simple dataWithContentsOfFile: method, I was also doing some data manipulation), and my app crashed. After I moved this process to a background thread, the app doesn't crash anymore. The only thing that happens is that the NSData I get is nil.

Is it possible that only my background thread is interrupted without affecting the main thread, or am I missing something? Also, can I count on this behaviour and just display an error message when the NSData is nil, without the app to crash? Thank you in advance.

Edit:

The log I get is:

malloc: * mmap(size=629800960) failed (error code=12) error: can't allocate region ** set a breakpoint in malloc_error_break to debug

The file I was using is about 250 MB large.

I know why it crashed on the main thread. My question is, why didn't it crash on a secondary thread?

Levi
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1 Answers1

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I guess it can depend on the crash, but if it is a problem of lack of memory (you can both be using too much memory or be creating too many objects) it will crash the entire app.

You should try to test the app with smaller files and see how it behaves.

David Carvalho
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  • Or perhaps employ alternative techniques to "read all the file into memory"? – trojanfoe Aug 06 '13 at 09:31
  • It has to be a memory issue, because it works with smaller files. I also checked it with Instruments, and the crash appeared around 300 MB allocated on an iPad 2 (when I read the file on the main thread). – Levi Aug 06 '13 at 10:12
  • Yeah, trojanfoe is right. In that case you better read the file by bits. Check NSInputStream: https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSInputStream_Class/Reference/Reference.html – David Carvalho Aug 06 '13 at 21:34