PureBasic Forum

Hi guys,

I am trying to speed up a program which parses millions of strings, but sometimes I get a crash




Any idea why?

Now j is verified that is it less than buffer which holds the string

EDIT: Comment removed, mis-read the post

When you assign a new string to *ptr\s, *ptr (which was pointing to *p which points to a string at *Buffer + j) may attempt to free the string memory that is pointed to by *p (before allocating new memory to receive the new string being assigned).

In my tests it would seem that because the new string Chr(0) is small it is just overwriting the previous string memory with the new value. If it instead tries to free the string memory and allocate new memory for the string it will cause a crash. I think it does this occasionally and when it does it causes your problem.

It might also occur if *p does not point to *Buffer (j <> 0). If an attempt is made to free the memory then, it would cause it to free memory at an invalid location (not the start) which is in the middle of the memory area pointed to by *Buffer.


If you are simply trying to overwrite the string at *Buffer + j with a #Null try using PokeS(*p, 0) instead. This will avoid any possible attempts to free and reallocate the affected memory.

@Demivec your logic is sound.
But I wanted to avoid using poke.

Is there any other way I can overwrite part of a string will null without using a library function?

Do all parsing in memory and assign to a string only when necessary.
Take care whether you are working in Unicode(2 bytes/char) or not.

yes that did the trick
and i should have thought about it myself
thanks for your help