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58 lines
2.0 KiB
C
58 lines
2.0 KiB
C
/* IFUNC generic definitions.
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This file is part of the GNU C Library.
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Copyright (C) 2017-2025 Free Software Foundation, Inc.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/* These macros are used to implement ifunc selection in C. To implement
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an ifunc function, foo, which returns the address of __foo_impl1 or
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__foo_impl2:
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#define foo __redirect_foo
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#include <foo.h>
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#undef foo
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#define SYMBOL_NAME foo
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#include <ifunc-init.h>
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extern __typeof (REDIRECT_NAME) OPTIMIZE (impl1) attribute_hidden;
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extern __typeof (REDIRECT_NAME) OPTIMIZE (impl2) attribute_hidden;
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static inline void *
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foo_selector (void)
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{
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if (condition)
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return OPTIMIZE (impl2);
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return OPTIMIZE (impl1);
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}
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libc_ifunc_redirected (__redirect_foo, foo, IFUNC_SELECTOR ());
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*/
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#define PASTER1(x,y) x##_##y
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#define EVALUATOR1(x,y) PASTER1 (x,y)
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#define PASTER2(x,y) __##x##_##y
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#define EVALUATOR2(x,y) PASTER2 (x,y)
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/* Basically set '__redirect_<symbol>' to use as type definition,
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'__<symbol>_<variant>' as the optimized implementation and
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'<symbol>_ifunc_selector' as the IFUNC selector. */
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#define REDIRECT_NAME EVALUATOR1 (__redirect, SYMBOL_NAME)
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#define IFUNC_SELECTOR EVALUATOR1 (SYMBOL_NAME, ifunc_selector)
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#define OPTIMIZE1(name) EVALUATOR1 (SYMBOL_NAME, name)
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#define OPTIMIZE2(name) EVALUATOR2 (SYMBOL_NAME, name)
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/* Default is to use OPTIMIZE2. */
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#define OPTIMIZE(name) OPTIMIZE2(name)
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