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dbd25fc75a
While gcc only emits warnings about unused static functions, Clang also emits such a warning when the functions are inlined. This is a bit annoying at certain places where functions are provided to manipulate multiple data types and are not yet used. Let's have a type modifier "__maybe_unused" which sets the "unused" attribute like the Linux kernel does. It's elegant as it allows the code author to indicate that it knows that this element might be unused. It works on variables as well, which is convenient to remove ifdefs around local variables in certain functions, but doesn't work on labels.
112 lines
3.1 KiB
C
112 lines
3.1 KiB
C
/*
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* include/common/compiler.h
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* This files contains some compiler-specific settings.
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*
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* Copyright (C) 2000-2009 Willy Tarreau - w@1wt.eu
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*
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* This 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, version 2.1
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* exclusively.
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*
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* This 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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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef _COMMON_COMPILER_H
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#define _COMMON_COMPILER_H
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/*
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* Gcc before 3.0 needs [0] to declare a variable-size array
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*/
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#ifndef VAR_ARRAY
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#if __GNUC__ < 3
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#define VAR_ARRAY 0
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#else
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#define VAR_ARRAY
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#endif
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#endif
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/* Support passing function parameters in registers. For this, the
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* CONFIG_REGPARM macro has to be set to the maximal number of registers
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* allowed. Some functions have intentionally received a regparm lower than
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* their parameter count, it is in order to avoid register clobbering where
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* they are called.
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*/
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#ifndef REGPRM1
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#if CONFIG_REGPARM >= 1 && __GNUC__ >= 3
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#define REGPRM1 __attribute__((regparm(1)))
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#else
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#define REGPRM1
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#endif
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#endif
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#ifndef REGPRM2
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#if CONFIG_REGPARM >= 2 && __GNUC__ >= 3
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#define REGPRM2 __attribute__((regparm(2)))
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#else
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#define REGPRM2 REGPRM1
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#endif
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#endif
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#ifndef REGPRM3
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#if CONFIG_REGPARM >= 3 && __GNUC__ >= 3
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#define REGPRM3 __attribute__((regparm(3)))
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#else
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#define REGPRM3 REGPRM2
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#endif
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#endif
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/* By default, gcc does not inline large chunks of code, but we want it to
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* respect our choices.
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*/
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#if !defined(forceinline)
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#if __GNUC__ < 3
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#define forceinline inline
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#else
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#define forceinline inline __attribute__((always_inline))
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#endif
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#endif
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/* silence the "unused" warnings without having to place painful #ifdefs.
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* For use with variables or functions.
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*/
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#define __maybe_unused __attribute__((unused))
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/*
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* Gcc >= 3 provides the ability for the programme to give hints to the
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* compiler about what branch of an if is most likely to be taken. This
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* helps the compiler produce the most compact critical paths, which is
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* generally better for the cache and to reduce the number of jumps.
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*/
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#if !defined(likely)
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#if __GNUC__ < 3
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#define __builtin_expect(x,y) (x)
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#define likely(x) (x)
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#define unlikely(x) (x)
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#elif __GNUC__ < 4 || __GNUC__ >= 5
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/* gcc 3.x and 5.x do the best job at this */
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#define likely(x) (__builtin_expect((x) != 0, 1))
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#define unlikely(x) (__builtin_expect((x) != 0, 0))
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#else
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/* GCC 4.x is stupid, it performs the comparison then compares it to 1,
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* so we cheat in a dirty way to prevent it from doing this. This will
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* only work with ints and booleans though.
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*/
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#define likely(x) (x)
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#define unlikely(x) (__builtin_expect((unsigned long)(x), 0))
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#endif
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#endif
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#endif /* _COMMON_COMPILER_H */
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