Get a pointer to the current function in C (gcc)?

I think you could build your table using strings (the function names) as keys, then look up by comparing with the __func__ builtin variable.

To enforce having a valid function name, you could use a macro that gets the function pointer, does some dummy operation with it (e.g. assigning it to a compatible function type temporary variable) to check that it's indeed a valid function identifier, and then stringifies (with #) the function name before being used as a key.

UPDATE:

What I mean is something like:

typedef struct {
  char[MAX_FUNC_NAME_LENGTH] func_name;
  //rest of the info here
} func_info;

func_info table[N_FUNCS];

#define CHECK_AND_GET_FUNC_NAME(f) ({void (*tmp)(int); tmp = f; #f})

void fill_it()
{
  int i = -1;
  strcpy(table[++i].func_name, CHECK_AND_GET_FUNC_NAME(foo));
  strcpy(table[++i].func_name, CHECK_AND_GET_FUNC_NAME(bar));
  //fill the rest
}

void lookup(char *name) {
  int i = -1;
  while(strcmp(name, table[++i]));
  //now i points to your entry, do whatever you need
}

void foo(int arg) {
  lookup(__func__);
  //do something
}

void bar(int arg) {
  lookup(__func__);
  //do something
}

(the code might need some fixes, I haven't tried to compile it, it's just to illustrate the idea)

void f() {
   void (*fpointer)() = &f;
}

#define FUNC_ADDR (dlsym(dlopen(NULL, RTLD_NOW), __func__))

And compile your program like

gcc -rdynamic -o foo foo.c -ldl

Here's a trick that gets the address of the caller, it can probably be cleaned up a bit. Relies on a GCC extension for getting a label's value.

#include <stdio.h>

#define MKLABEL2(x) label ## x
#define MKLABEL(x) MKLABEL2(x)
#define CALLFOO do { MKLABEL(__LINE__): foo(&&MKLABEL(__LINE__));} while(0)

void foo(void *addr)
{
    printf("Caller address %p\n", addr);
}

int main(int argc, char **argv)
{
    CALLFOO;
    return 0;
}