Thread: Double Pointers and dynamic memory allocation

Hello I am new to C and we are currently covering double pointers and memory allocation. Currently getScrabbleWords is not working. when I compile with commented code (Main() works fine) I get a segmentation fault. Could I get guidance of where I have flukes?

This is the purpose of getScrabbleWords:
char **getScrabbleWords(char **allWords, char letters[]): This function takes an array of char* values (i.e. strings) representing all the words read from wordlist.txt. Each of these words is tested by callingcanWeMakeIt as a helper function, and pointers to the words that can be made are put into an array, myWords. Note, copies of the words are not made! In order to indicate the end of myWords, we terminate with a NULL pointer. Thus, if N words can be made from letters then myWords should have length N+1.

Are you sure the error is here? After all, you know you have a NULL pointer hanging around -- if a loop somewhere else goes awry and tries to use that NULL pointer, then that would be the (or a, at least) problem.

The error has to be there. So I should check to see if I have a null pointer in the loop and from there fix whatever is occurring? Be in a general sense is my looping and structure of my for-loop good?

There is an error in that your for loop will not go through your entire allWords array -- i will never go past 1, because sizeof(allWords) and sizeof(allWords[0]) will be the same number, specifically the size of a pointer on your system.

There is no reason (based on what you've said) to believe that the only error is here. (I did read where you said that it ran when you commented out this code; that's not particularly relevant.)

Oh i saw that. Thanks well you are saying it might be other areas of the code. Could you exam what I have and lead me in the right direction? I can post pics of the code or could upload the code if you are willing to assist me further.

The function here looks well-formed in that when you get to the end you've got exactly what the specs say you should have -- an array of pointers with the last one being NULL. There don't appear to be any problematic lines here. My instinct is that your segfault is from some other code not respecting the boundaries and trying to follow that NULL pointer.

Your debugger should be telling you what line caused the segfault (and if you're not using a debugger, now would be an excellent time to start), and that will most likely give you some clues.

Okay Ill try to install a debugger. Thanks Man.