142 lines
5.6 KiB
C
142 lines
5.6 KiB
C
/*
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* Copyright (c) 2003, 2006, 2008, 2009
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* The President and Fellows of Harvard College.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef _CDEFS_H_
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#define _CDEFS_H_
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/*
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* Some miscellaneous C language definitions and related matters.
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*/
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/*
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* Build-time assertion. Doesn't generate any code. The error message
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* on failure is less than ideal, but you can't have everything.
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*/
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#define COMPILE_ASSERT(x) ((void)sizeof(struct { unsigned : ((x)?1:-1); }))
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/*
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* Handy macro for the number of elements in a static array.
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*/
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#define ARRAYCOUNT(arr) (sizeof(arr) / sizeof((arr)[0]))
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/*
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* Tell GCC how to check printf formats. Also tell it about functions
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* that don't return, as this is helpful for avoiding bogus warnings
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* about uninitialized variables.
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*/
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#ifdef __GNUC__
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#define __PF(a,b) __attribute__((__format__(__printf__, a, b)))
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#define __DEAD __attribute__((__noreturn__))
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#define __UNUSED __attribute__((__unused__))
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#else
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#define __PF(a,b)
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#define __DEAD
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#define __UNUSED
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#endif
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/*
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* Material for supporting inline functions.
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*
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* A function marked inline can be handled by the compiler in three
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* ways: in addition to possibly inlining into the code for other
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* functions, the compiler can (1) generate a file-static out-of-line
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* copy of the function, (2) generate a global out-of-line copy of the
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* function, or (3) generate no out-of-line copy of the function.
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*
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* None of these alone is thoroughly satisfactory. Since an inline
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* function may or may not be inlined at the compiler's discretion, if
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* no out-of-line copy exists the build may fail at link time with
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* undefined symbols. Meanwhile, if the compiler is told to generate a
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* global out-of-line copy, it will generate one such copy for every
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* source file where the inline definition is visible; since inline
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* functions tend to appear in header files, this leads to multiply
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* defined symbols and build failure. The file-static option isn't
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* really an improvement, either: one tends to get compiler warnings
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* about inline functions that haven't been used, which for any
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* particular source file tends to be at least some of the ones that
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* have been defined. Furthermore, this method leads to one
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* out-of-line copy of the inline function per source file that uses
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* it, which not only wastes space but makes debugging painful.
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*
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* Therefore, we use the following scheme.
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*
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* In the header file containing the inline functions for the module
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* "foo", we put
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*
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* #ifndef FOO_INLINE
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* #define FOO_INLINE INLINE
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* #endif
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*
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* where INLINE selects the compiler behavior that does *not* generate
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* an out-of-line version. Then we define the inline functions
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* themselves as FOO_INLINE. This allows the compiler to inline the
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* functions anywhere it sees fit with a minimum of hassles. Then,
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* when compiling foo.c, before including headers we put
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*
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* #define FOO_INLINE // empty
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*
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* which causes the inline functions to appear as ordinary function
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* definitions, not inline at all, when foo.c is compiled. This
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* ensures that an out-of-line definition appears, and furthermore
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* ensures that the out-of-line definition is the same as the inline
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* definition.
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*
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* The situation is complicated further because gcc is historically
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* not compliant with the C standard. In C99, "inline" means "do not
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* generate an out-of-line copy" and "extern inline" means "generate a
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* global out-of-line copy". In gcc, going back far longer than C99,
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* the meanings were reversed. This eventually changed, but varies
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* with compiler version and options. The macro __GNUC_STDC_INLINE__
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* is defined if the behavior is C99-compliant.
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*
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* (Note that inline functions that appear only within a single source
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* file can safely be declared "static inline"; to avoid whining from
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* compiler in some contexts you may also want to add __UNUSED to
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* that.)
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*/
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#if defined(__GNUC__) && !defined(__GNUC_STDC_INLINE__)
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/* gcc's non-C99 inline semantics */
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#define INLINE extern inline
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#elif defined(__STDC__) && __STDC_VERSION__ >= 199901L
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/* C99 */
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#define INLINE inline
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#else
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/* something else; static inline is safest */
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#define INLINE static __UNUSED inline
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#endif
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#endif /* _CDEFS_H_ */
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