[fpc-devel] Access Violation withnested DLL'scompiledbyFPC(andsome more info on bug #4538)

[Jonas Maebe]

On 15 dec 2005, at 05:45, L505 wrote:

> Why does it generate a DecStringRef before you assigned the string?  
> What if it is the
> first time and you are already at 0, it can't decrement it to -1  
> can it?

The reference count can never be zero, because when it becomes zero  
the string is freed and replaced with a nil pointer. Calling  
DecStringRef() on a nil pointer does nothing.

> Does the reference count start at 0, or 1?

All ansistring variables are initialised with nil.

> That seems like it isn't doing anything useful, since we are  
> incrementing and
> decrementing by one, every time we assign a string.

An ansistring is a pointer which points to a string. Many different  
ansistring variables can point to the same string, and then the  
reference count of this ansistring will be equal to the amount of  
ansistring variables pointing to it.

s := t; (-> reference count of ansistring to which s points is  
decreased by 1 and freed if reference count became zero, the one to  
which t points is increased by 1)
q := t; (-> reference count of ansistring to which q points is  
decreased by 1 and freed if reference count became zero, the one to  
which t points is again increased by 1)


Jonas