C Interview Questions and Answers


If I have a char * variable pointing to the name of a function ...

If I have a char * variable pointing to the name of a function, how can I call that
function? Code like

extern int func(int, int);

char *funcname = "func";

int r = (*funcname)(1, 2);


r = (*(int (*)(int, int))funcname)(1, 2);

doesn't seem to work.

By the time a program is running, information about the names of its functions and
variables (the ``symbol table'') is no longer needed, and may therefore
not be available. The most straightforward thing to do, therefore, is to maintain
that information yourself, with a correspondence table of names and function pointers:

int one_func(), two_func();

int red_func(), blue_func();

struct { char *name; int (*funcptr)(); } symtab[] = {

"one_func", one_func,

"two_func", two_func,

"red_func", red_func,

"blue_func", blue_func,


Then, search the table for the name, and call via the associated function pointer,
with code like this:

#include <stddef.h>

int (*findfunc(char *name))()


int i;

for(i = 0; i < sizeof(symtab) / sizeof(symtab[0]); i++) {

if(strcmp(name, symtab[i].name) == 0)

return symtab[i].funcptr;


return NULL;



char *funcname = "one_func";

int (*funcp)() = findfunc(funcname);

if(funcp != NULL)


Posted by:Richards