Best way to handle memory allocation in C?

Question

I think I\'ve got a good grasp on how to handle memory in C++ but doing it in C is different I\'m a bit off.

In C++ I\'ve got constructors and destructors, I\'ve got the

Answer 1

I'm not quite sure what you're asking, but C is pretty straightforward:

struct Foo *f0 = malloc(sizeof(*f));   // alloc uninitialized Foo struct
struct Foo *f1 = calloc(1,sizeof(*f)); // alloc Foo struct cleared to all zeroes

//You usually either want to clear your structs using calloc on allocation, or memset. If 
// you need a constructor, just write a function:
Foo *Foo_Create(int a, char *b)
{
   Foo *r = calloc(1,sizeof(*r));
   r->a = a;
   r->b = strdup(b);
   return r;
}

Here is a simple C workflow with arrays:
struct Foo **foos = NULL;
int n_foos = 0;
...
for(i = 0; i < n_foos; ++i)
{
   struct Foo *f = calloc(1,sizeof(*f));
   foos = realloc(foos,sizeof(*foos)*++n_foos); // foos before and after may be different
   foos[n_foos-1] = f;
}

If you get fancy, you can write macros to help:

#define MALLOCP(P) calloc(1,sizeof(*P)) // calloc inits alloc'd mem to zero

A couple of points:

• malloc, calloc, realloc, etc. all use free(), so managing these things is easy. Just be consistant.
• performance for mallocs can be slow. Someone posted a link on this above. These days fast multi-threaded allocations is key, see tcmalloc et al. You probably don't have to worry about this.
• on a modern virtual memory architecture, malloc will almost never fail unless you are out of virtual address space. If this happens, switch to 64bit ;)
• Make sure you're using a system that has bounds checking, wiped free values, leak tracking and all that good stuff (see valgrind, win32 debug heap, etc.)