Question

My application falls over when I make the following call to strcat any ideas why?

char *encryptedLine[255] = {0};  
char encryptedLString[8];        
sprintf(encryptedLString, "%08lX", L);
strcat(*encryptedLine, encryptedLString);  

Answer 1

*encryptedLine is NULL pointer: it needs to point a char buffer.

*encyptedLine is equivalent to encryptedLine[0], which is the first entry in the array of char* encryptedLine:

char *encryptedLine[255] = { 0 };

which is a NULL pointer.

To fix, either change to:

char encryptedLine[255] = { 0 };

strcat(encryptedLine, encryptedString);

or:

encryptedLine[0] = malloc(255);
strcat(*encryptedLine, encryptedString);

I think you also need to increase the size of encryptedLString by 1 as:

sprintf(encryptedLString, "%08lX", L);

will attempt to write 9 characters: 8 specified by the format plus 1 for the null terminator:

char encryptedLString[9];