Question

Possible Duplicate:
How do I work with dynamic multi-dimensional arrays in C?
pointer to array type, c

If my C89 ANSI (e.g. not C99) C code declares a variable AND allocates memory using:

char myArray[30000][3];

Is there a way I can de-couple the declaration from the memory allocation by using malloc()? For example (and pardon my newbie-ness):

char *myArray;
int i, arrayLength;
...
/* compute arrayLength */
...
myArray = malloc( sizeof(char) * arrayLength * 3);
for (i=0; ii<arrayLength; i++) 
   strncpy(myArray[i], "ab", 3);
...
free(myArray);

The goal is to create myArray looking like, for example:

myArray[0] = "ab"
myArray[1] = "ab"
myArray[2] = "ab"
...
myArray[arrayLength-1] = "ab"

Is that the right approach?

Answer 1

It looks like you want to make the first array size a variable run-time value (specified by arrayLength), while keeping the second size as fixed compile-time value (3). In that specific situation it is easy

char (*myArray)[3];
int arrayLength;
...
/* compute arrayLength */
...
myArray = malloc(arrayLength * sizeof *myArray);
for (i = 0; i < arrayLength; ++i) 
  strcpy(myArray[i], "ab");
...
free(myArray);

Things will get more complicated if you decide to make the second array size a run-time value as well.

P.S. strncpy is not supposed to serve as a “safe” version of strcpy (see https://stackoverflow.com/a/2115015/187690, https://stackoverflow.com/a/6987247/187690), so I used strcpy in my code. But you can stick with strncpy if you so desire.