On 7/29/05 7:03 AM, Norio Ota didst favor us with:
> I'm wondering why a released CFDataRef returns a valid value using
> CFDataGetBytePtr?
> Does CFRelease actually deallocate/free memory which is allocated and
> copied from source memory?
The contents of the memory are not overwritten just because it was freed
unless you're using some kind of special debug library that writes junk to
freed memory. It may be valid immediately after you release it, but you have
no way to know how long it will be before it's overwritten and becomes
invalid.
Larry
> If not, where and how do I free the memory that the dataRef has been
> holding?
>
> int main ()
> {
> const char* kMyName = "Norio Ota";
> size_t len = strlen (kMyName);
> char * newString, *dStr;
> CFDataRef data;
>
> newString = (char*) malloc (len + 1);
> memcpy (newString, kMyName, len);
> newString[len] = '\0';
>
> data = CFDataCreate (kCFAllocatorDefault, newString, len +1);
> CFShow (data);
> fprintf (stderr, "newString is %s\n", newString);
> free (newString);
>
> fprintf (stderr, "freed newString is %s\n", newString);
>
> CFShow (data);
> CFRelease (data);
>
> dStr = CFDataGetBytePtr (data);
> fprintf (stderr, "after releasing, stored newString is %s\n", dStr);
>
> return 0;
> }
>
> The log is something like below.
>
>
> <CFData 0x11011d0 [0xa01c00e0]>{length = 10, capacity = 10, bytes =
> 0x4e6f72696f204f746100}
> newString is Norio Ota
> freed newString is
> <CFData 0x11011d0 [0xa01c00e0]>{length = 10, capacity = 10, bytes =
> 0x4e6f72696f204f746100}
> after releasing, stored newString is Norio Ota
>
>
> As you can see, despite the data was released before being called
> CFDataGetBytePtr, it returns a value which seems to be valid.
>
> Thanks,
> Norio
>
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