How to relate X-macro to array of function pointer

Question

I applied X-macro mechanism to get enumeration-to-string relation.

#define CMD_TABLE \
                     X(cmd_A)\
                     X(cmd_B)\
////////////////////////////////////
typedef enum
{
    EMPTY, 
#define X(x) x,
    CMD_TABLE
#undef X
}cmd_t;
////////////////////////////////////
const static struct
{
    char* name;
    cmd_t index;
} conversionMap[] = {
#define X(x) {#x, x},
        CMD_TABLE
#undef X
};

Then, this function converts string to enum.

cmd_t str2enum(const char* str);

Finally, corresponding function is called by treating enum as the index of array.

(*func[index])();

This method has a big problem that it force programmer to remember enum-to-function mapping relationship.

In other words, in initialization stage, the order of following functions

void (*func[])(void) = 
{
    &cmd_A_function,
    &cmd_B_function,
};

needs to be as same as that of CMD_TABLE.

Further, once CMD_TABLE grows, code is getting worse to maintain because

1. if a command is not going to support, people might delete wrong line in array of function pointer.

2. if I want to know what does cmd_Z do, I have to count up from 1 to 26.

3. list of CMD_TABLE and void (*func[])(void) will be far away from each other such that programmer needs to write code in two places in order to add one feature.

Answer 1

You have already used X-macro twice.
You can use it a third time.
Here is a proposal how to do that, using the ugly undef-using pattern you applied the first two times:

void (*func[])(void) = 
{
#define X(x) &x##_function,
    CMD_TABLE
#undef X
};