SVGQuartzRenderer::parse is not thread safe about svgquartzrenderer HOT 4 CLOSED

Thanks ansoni. Now, there are no class variables in Objective C. Perhaps you meant static; but svgXml is not static.
So, not sure what the issue is here......

from svgquartzrenderer.

Indeed class scope was the wrong wording. Instance scope is how I would describe it.

So we have the NSData* svgXml declaration in the header file declared as a private variable. So, when I create an instance of SVQuartzRenderer, it will have a single svgXm variable.

The svgXml pointer gets initialized at the beginning of the parse method, then the data gets parsed which might take a few millisseconds and then the pointer is free'd. If called twice from two different threads at the exact same time, I would expect one or both concurrent method calls to fail with this potential scenario:

1st call creates an NSData object and writes the address to the svgXml variable.
1st call goes on to use the variable.
2nd call creates a new NSData object and overwrites the existing svgXml pointer.
1st call potentially could potentially error here.
2nd call goes on to use the variable.
1st call releases the svgXML variable
2nd call might go bad here?
2nd call tries to release svgXML variable.

I will write some code to verify this behavior so you don't need to waste time if this is Obj-C ignorance on my part.

from svgquartzrenderer.

Hi Anonsi,
The parser is not designed to be thread safe. If two threads need the same parser, they must implement locking
to avoid data corruption.

from svgquartzrenderer.

BTW, Anonsi, private just means that derived classes do not have access to the variable. It doesn't mean that two instances of the parser share the same variable. If it is marked static, then it will be shared.

from svgquartzrenderer.