How to do a computed goto in an inline function in GCC

dragons.c

#include <stdio.h>
#include <stdlib.h>

/*
 * How to do a computed goto in an inline function.
 * "Here be Dragons"
 */

 /* 
 * This is used to keep the compiler from 
 * optimizing out the label code blocks because
 * they looks unreachable.
 */
int unknown = 1;

/*
 * Instantiate a label 
 * 
 * This uses linker trickery to put the address
 * of the code block in a separate ELF section 
 * called my_jump_table
 */
#define label_me() \
	asm volatile (	\
		"1: \n" \
		".section my_jump_table,\"a\"\n" \
		".align 4\n" \
		".long 1b\n" \
		".text\n"  \
		: : : "memory") 
/*
 * Start a new block in the jump table
 * 
 * Because each instance of the inline function
 * needs its own set of jump table entries for
 * all the labels, we keep a different block in
 * the jump table for each instance of the inline
 * function.
 * 
 * This little nuggets open a new block in the 
 * jump table by writing a jump table block header
 * which is a single long with the address of block
 * instantiation (unused except for debugging) and 
 * returning the address of the first entry - 
 * which stores the address of the first label for
 * this block.
 */
#define start_here(_table_addr) \
	asm volatile ( \
		".section my_jump_table,\"a\"\n" \
		".align 4\n" \
		"1: .long 1b\n" \
		".text \n" \
		"movl $1b, %0\n" \
		: "=r"(_table_addr): : "memory"); \
		_table_addr++

/*
 * Change PC (jump) to the supplied address.
 * This is simply a computed goto. 
 */
#define jump(_addr) \
	asm volatile ( \
		"jmp *%0\n" : : "r"(_addr) : "memory")

#define always_inline inline __attribute__((always_inline))

#define LABELS_NUM 8

static always_inline int test(void) 
{
	int labels[LABELS_NUM] = {1, 0 ,1, 0, 1 ,1, 0, 2};
	int i = 0;
	void ** p;

	start_here(p);

	printf("Jump table address for this instance is %p\n", p);

	for(i=0; i< LABELS_NUM; i++) {

		// printf("p[%d] is %p\n", i, p[i]);

		jump(p[labels[i]]);

		printf("Not reached!\n");

		label_me();
		printf("Hello world! %d\n", i);
		if(unknown) continue;

		label_me();
		printf("Middle ground %d\n", i);
		if(unknown) continue;

		label_me();
		printf("Last stop! %d\n", i);
		break;
	}

	return 0;
}

int main(void) 
{
	printf("First call...\n");
	test();
	printf("Done.\n\n");

	printf("2nd call...\n");
	test();
	printf("Done.\n\n");

	printf("3rd call...\n");
	test();
	printf("Done.\n\n");

	return EXIT_SUCCESS;
}