Segmentation fault on Lion creating NSData from RubyCocoa with any bytes > 127

Question

The following RubyCocoa is fine on Max OS X 10.6, but segfaults on 10.7

require 'osx/cocoa'
include OSX
bytes = [128].pack('i1')
NSData.alloc.initWithBytes_length(bytes, bytes.length)

In all cases it works when the top bit is not set. In fact NSData.alloc seems to fail when passed a buffer where any of the bytes have the top bit set.

The version of Ruby is 1.8.7 on both OS's, so I'm at a loss to diagnose why NSData is interpreting the buffer differently. Can anyone shed any light?

Playing with thus further, I can find no call to an NSData or NSMutableData constructor that works, nor does CFDataCreate. — Duncan McGregor, Jul 22 '11 at 06:33

score 1 · Answer 1 · answered Jul 21 '11 at 11:44

1

You should probably go for MacRuby as it will replace RubyCocoa. It's possible that RubyCocoa does not (and will never) work properly on Lion.

I don't have any MacRuby experience with Lion yet, but chances are good that it will work.

answered Jul 21 '11 at 11:44

Koraktor

41,357
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Indeed, but as I have a significant RubyCocoa codebase, and MacRuby is still not released, I'm currently hosed. – Duncan McGregor Jul 21 '11 at 11:53

score 1 · Answer 2 · answered Aug 03 '11 at 19:55

MacRuby is still unfinished - it just doesn't work with some of the ruby code I work with. I've run into the same NSData problem, and I was able to create a CFData instance which appears ok with the following code

gem 'RubyInline'
require 'inline'

class CFDataWrapper
  begin 
    inline do |builder|
      builder.include "<CoreFoundation/CoreFoundation.h>"
      builder.c_raw_singleton "

      static VALUE fromString(int argc, VALUE *args){
        CFDataRef d = CFDataCreate(NULL, RSTRING_PTR(args[0]), RSTRING_LEN(args[0]));    

        VALUE result;
        char type = '@';
        ocdata_to_rbobj(Qnil,&type, (const void *)&d, &result, false) ;
        return result;
      }
    "
    end
  end
end
bytes = [128].pack('i1')
data = CFDataWrapper.fromString(bytes)
puts data.inspect

The output from inspect is different from under 10.6 but I can pass it back into methods that expect NSData instances and they appear to work, call NSData methods on it etc. Beyond this toy script it works a script i use to populate core data documents, where one of the entities has a binary data attribute

Thanks, maybe Lion changed something that affected both – Duncan McGregor Sep 18 '11 at 15:25 — Duncan McGregor, Sep 18 '11 at 15:25

ergosys · Answer 3 · 2011-08-04T02:22:17.533

0

I will guess that the problem is actually pack corrupting memory because it is not handling the signed overflow in a good way. Some things to try that may lead you to the answer:

try pack('C1')
Dump out bytes, compare to irb's output.
call some other function which allocates memory right after the pack (not using bytes at all).

edited Aug 04 '11 at 02:22

answered Aug 03 '11 at 20:28

ergosys

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I don't think it is pack, as that is standard Ruby – Duncan McGregor Sep 18 '11 at 15:24

score 0 · Accepted Answer · answered Sep 18 '11 at 15:26

0

This is fixed in RubyCocoa 1.0.2

answered Sep 18 '11 at 15:26

Duncan McGregor

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Segmentation fault on Lion creating NSData from RubyCocoa with any bytes > 127

4 Answers4