Append items to an array with a macro, in C

Question

I have an array (C language) that should be initialized at compile time.

For example:

DECLARE_CMD(f1, arg);
DECLARE_CMD(f2, arg);
         


        

Answer 1

You can actually use a single macro to set the function pointers, do the function declaration, set up enums to access the function pointer and strings to use in error messages and later you can use it in a switch().

#define X_MACRO(OP) \
  OP(addi, int x, int y) \
  OP(divi, int x, int y) \
  OP(muli, int x, int y) \
  OP(subi, int x, int y)

#define AS_FUNC_PTR(x,...) x,
#define AS_FUNC(x,...) int x(__VA_ARGS__);
#define AS_STRINGS(x,...) #x,
#define AS_ENUMS(x,...) ENUM_##x,

X_MACRO(AS_FUNC)

typedef int (*foo_ptr_t)( int, int );
foo_ptr_t foo[] = { X_MACRO(AS_FUNC_PTR) };

char *foo_strings[] = { X_MACRO(AS_STRINGS) };

enum foo_enums { X_MACRO(AS_ENUMS) };

/** example switch()
#define AS_CASE(x,...) ENUM_x : x(i,j);break;
switch (my_foo_enum){
  X_MACRO(AS_CASE)
  default: do_error();
}
**/