/* IFUNC generic definitions.

   This file is part of the GNU C Library.

   Copyright (C) 2017-2018 Free Software Foundation, Inc.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

/* These macros are used to implement ifunc selection in C.  To implement

   an ifunc function, foo, which returns the address of __foo_impl1 or

   __foo_impl2:

   #define foo __redirect_foo

   #include <foo.h>

   #undef foo

   #define SYMBOL_NAME foo

   #include <ifunc-init.h>

   extern __typeof (REDIRECT_NAME) OPTIMIZE (impl1) attribute_hidden;

   extern __typeof (REDIRECT_NAME) OPTIMIZE (impl2) attribute_hidden;

   static inline void *

   foo_selector (void)

   {

     if (condition)

      return OPTIMIZE (impl2);

     return OPTIMIZE (impl1);

   }

   libc_ifunc_redirected (__redirect_foo, foo, IFUNC_SELECTOR ());

*/

#define PASTER1(x,y)	x##_##y

#define EVALUATOR1(x,y)	PASTER1 (x,y)

#define PASTER2(x,y)	__##x##_##y

#define EVALUATOR2(x,y)	PASTER2 (x,y)

/* Basically set '__redirect_<symbol>' to use as type definition,

   '__<symbol>_<variant>' as the optimized implementation and

   '<symbol>_ifunc_selector' as the IFUNC selector.  */

#define REDIRECT_NAME	EVALUATOR1 (__redirect, SYMBOL_NAME)

#define OPTIMIZE(name)	EVALUATOR2 (SYMBOL_NAME, name)

#define IFUNC_SELECTOR	EVALUATOR1 (SYMBOL_NAME, ifunc_selector)