va_list, va_start, va_pass!!! or how to pass variable-argument list to next va-function

#include <stdarg.h>

/* Replace with your best guesstimate of the max total unnamed argument size */
#define VA_MAX_SIZE 256

struct _va_block_s {
    char _dummy[VA_MAX_SIZE];
};

#define va_pass(args) va_arg(args, struct _va_block_s)


/* Example usage */
#include <stdio.h>

int my_printf(const char *format, ...) {
    int ret_val;
    va_list args;

    va_start(args, format);
    /* Stuff approximately 60 more arguments than we actually need... */
    ret_val = printf(format, va_pass(args));
    va_end(args);
    return ret_val;
}

my_printf("%lf %c %ld", 4.7, 'A', -17);

push    -17             ; Pass an int (pointer-sided argument) (4 bytes)
push    65              ; Pass a char (aligned to pointer-sized, still 4 bytes)
sub     esp, 8          ; Reserve room for a double-sized argument (8 bytes)
fstp    qword ptr[esp]  ; Pass a double
push    offset format   ; Pass the format string pointer (4 bytes)
call    my_printf       ; Nothing on the parameter stack indicates total vararg size or types;
...                     ;   it's just a block of memory with known base but unknown size
add     esp, 20         ; *Somewhere* after the call, clean up the stack, rewinding it by the total
                        ;   size of passed arguments. This number changes based on the number of
                        ;   arguments actually passed, but the instruction is not guaranteed to
                        ;   immediately follow the call, or even be this exact instruction...

#define my_printf(...) { \
	/* Declare local variables, do something */ \
	printf(__VA_ARGS__); \
	/* Do something else */ \
}

/* Or */

#define my_printf(...) ( \
	/* Evaluate some expressions separated with a comma */
	printf(__VA_ARGS__), \
	/* Evaluate the return result */
)