memcpy c++ - crashing

Question

I have a very simple routine (at least should be simple)

I create a large char array and I am copying data to it as I receive it moving. After about the third iteration the app crashes.

first create a large buffer

_buffer = new char(7931880);

...

void writeData(char* newData,size_t size)
{
  memcpy(_buffer,newData,size); //this call succeeds the first 4 times then fails bytes received
 _buffer+=size;                 //(size) is never larger than 16000
}

Answer 1

_buffer = new char(7931880);

This is a pointer to a SINGLE character. To get an array use

_buffer = new char[7931880];

And turn on compiler warnings to detect the overflow.

Answer 2

You are dynamically allocating a single char with value 7931880 . Making an assumption that your buffer should be a little more than a single char (not much of a buffer), perhaps you were looking for _buffer = new char[7931880]; . This would allocate 7931880 char s.