How do you know how much space to allocate with malloc()?

Question

I\'m a total C newbie, I come from C#. I\'ve been learning about memory management and the malloc() function. I\'ve also came across this code:

char         


        

Answer 1

Well, for a start, sizeof(char) is always 1, so you could just malloc(3).

What you're allocating there is enough space for three characters. But keep in mind you need one for a null terminator for C strings.

What you tend to find is things like:

#define NAME_SZ 30
: : :
char *name = malloc (NAME_SZ+1);

to get enough storage for a name and terminator character (keeping in mind that the string "xyzzy" is stored in memory as:

+---+---+---+---+---+----+
| x | y | z | z | y | \0 |
+---+---+---+---+---+----+

Sometimes with non-char based arrays, you'll see:

int *intArray = malloc (sizeof (int) * 22);

which will allocate enough space for 22 integers.