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/* IFUNC generic definitions.
This file is part of the GNU C Library.
Copyright (C) 2017-2019 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
<https://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)
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