a strange problem in my code

hi,
I have a new problem in my code.

I try to call a function in a loop:
=========================================
while( read_image )
{
read_chunk();
}

and the function is to do:
========================================
chunk_idat idat;
idat.data_block = new unsigned char[ 8186 ];
read_image.read( (char*) &idat, (int) chunk_length );

delete [] idat.data_block;


break;
=========================================

the strcut is:

struct chunk_idat
{

unsigned char flag_code;
unsigned char check_bit;
unsigned char* data_block;
unsigned long int check_value;

};


----------------------------------------
when I executed this code, a error message wiil pop up and termined it .
I found that the error is caused when the first time finished ( before the sencond time looping )

ps: the code is much longer than above, so cannnot post it

Hey there. I believe the problem is when you make the call to read_image.read(). The first parameter you passed in is the (char*)&idat, try passing the (char*)&idat.data_block instead. Hope this helps.

well, I found the problem is when I "new" a size to "unsigned char* data_block;"
If I use a fix number then there is no problem occured.

here are my code ( I am writing a program to read and write PNG files)
please help me to solve the problem


( I changed the code structure from using "struct to class" )