On Oct 15, 2008, at 7:31 PM, James Trankelson wrote:
I have a question about method parameters in Objective C. A long time
ago, I had a method like the following:
-(void) foo:(float)val { }
... and when I would call it ([inst foo:0.001], for example), the
value inside the foo method would NOT be 0.001. At the time, I
believed there to be an Objective C requirement that parameters to
methods need to be pointers to objects, not primitive values.
Nope, no such requirement.
So, I've got the following method:
+ (void)done:(MyObj*)dObj structure:(void*)pStruct
... and when I call it with a "structure" parameter, say a malloc'ed
char* at address 0x171eb070, as soon as I step into this method, the
address is no longer 0x171eb070, but some garbage value that causes
all sorts of trouble. Here's to hoping someone can tell me why this
doesn't work...
Do a clean build. Pay attention to and address _all_ warnings.
In particular, the compiler may warn about sending messages that
haven't been declared. It may assume parameter types that aren't the
same as the real method, which can cause garbage to be received.
Also, be careful when stepping in the debugger. If you step by
instruction, you may need to step a few instructions into a function/
method implementation before the stack frame is set up so that the
debugger can really interpret the values of arguments. In other
words, for the first few instructions it may show you garbage-seeming
values for arguments and locals.
Cheers,
Ken
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