Recursively freeing C structs

Question

I have a struct that only contains pointers to memory that I\'ve allocated. Is there a way to recursively free each element that is a pointer rather than calling free on eac

Answer 1

Such functionality is not built in to C, but you can cheat a little bit by abusing the macro preprocessor:

#define XX_MODEL_POINTERS do { \
  xx(vertices); xx(normals); xx(uv_coords); xx(quads); xx(triangles); \
} while(0)

To allocate:

model *mdl = malloc(sizeof(*mdl));
assert(mdl);
#define xx(N) mdl->N = malloc(sizeof(*mdl->N)); assert(mdl->N)
XX_MODEL_POINTERS;
#undef xx

To free:

assert(mdl);
#define xx(N) free(mdl->N); mdl->NULL
XX_MODEL_POINTERS;
#undef xx
free(mdl);
mdl = NULL;

The nasty bit is that the definition of struct model and the definition of XX_MODEL_POINTERS can become mutually inconsistent, and there's no way to catch it. For this reason it's often better to generate the definition of XX_MODEL_POINTERS by parsing a .h file somewhere.

Metaprogramming in C is never easy.