#ifndef PICKNO
# define PICKNO 1
#endif
#if PICKNO == 2
# define PICK(fn1, fn2) #fn2
#else
# define PICK(fn1, fn2) #fn1
#endif
#ifdef __x86_64__
# define IFUNC_ASM(fn) "\tleaq " fn "(%rip), %rax\n\tretq\n"
#endif
#define IFUNC(name, globl, fn1, fn2) \
extern __typeof (fn1) fn1 __attribute__((used));	\
extern __typeof (fn2) fn2 __attribute__((used));	\
extern __typeof (fn1) name;				\
asm (globl " " #name "\n"				\
     "\t.type " #name ", @gnu_indirect_function\n"	\
     #name ":\n"					\
     IFUNC_ASM (PICK (fn1, fn2))			\
     "\t.size " #name ", .-" #name "\n")
#define IFUNC_LOCAL(name, fn1, fn2) IFUNC(name, ".local", fn1, fn2)
#define IFUNC_GLOBAL(name, fn1, fn2) IFUNC(name, ".globl", fn1, fn2)

static int foo1 (void) { return 1; }
static int foo2 (void) { return 2; }

IFUNC_LOCAL (foo, foo1, foo2);

extern void abort (void);

int
main (void)
{
  if (foo () != PICKNO)
    abort ();
  return 0;
}