lib/compiler.h

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #ifndef COMPILER_H
  18 #define COMPILER_H 1
  19
  20 #if __GNUC__ && !__CHECKER__
  21 #define NO_RETURN __attribute__((__noreturn__))
  22 #define OVS_UNUSED __attribute__((__unused__))
  23 #define PRINTF_FORMAT(FMT, ARG1) __attribute__((__format__(printf, FMT, ARG1)))
  24 #define STRFTIME_FORMAT(FMT) __attribute__((__format__(__strftime__, FMT, 0)))
  25 #define MALLOC_LIKE __attribute__((__malloc__))
  26 #define ALWAYS_INLINE __attribute__((always_inline))
  27 #define WARN_UNUSED_RESULT __attribute__((__warn_unused_result__))
  28 #define SENTINEL(N) __attribute__((sentinel(N)))
  29 #define OVS_LIKELY(CONDITION) __builtin_expect(!!(CONDITION), 1)
  30 #define OVS_UNLIKELY(CONDITION) __builtin_expect(!!(CONDITION), 0)
  31 #else
  32 #define NO_RETURN
  33 #define OVS_UNUSED
  34 #define PRINTF_FORMAT(FMT, ARG1)
  35 #define STRFTIME_FORMAT(FMT)
  36 #define MALLOC_LIKE
  37 #define ALWAYS_INLINE
  38 #define WARN_UNUSED_RESULT
  39 #define SENTINEL(N)
  40 #define OVS_LIKELY(CONDITION) (!!(CONDITION))
  41 #define OVS_UNLIKELY(CONDITION) (!!(CONDITION))
  42 #endif
  43
  44 #ifdef __CHECKER__
  45 /* "sparse" annotations for mutexes and mutex-like constructs.
  46  *
  47  * In a function prototype, OVS_ACQUIRES(MUTEX) indicates that the function
  48  * must be called without MUTEX acquired and that it returns with MUTEX
  49  * acquired.  OVS_RELEASES(MUTEX) indicates the reverse.  OVS_MUST_HOLD
  50  * indicates that the function must be called with MUTEX acquired by the
  51  * caller and that the function does not release MUTEX.
  52  *
  53  * In practice, sparse ignores the MUTEX argument.  It need not even be a
  54  * valid expression.  It is meant to indicate to human readers what mutex is
  55  * being acquired.
  56  *
  57  * Since sparse ignores MUTEX, it need not be an actual mutex.  It can be
  58  * any construct on which paired acquire and release semantics make sense:
  59  * read/write locks, temporary memory allocations, whatever.
  60  *
  61  * OVS_ACQUIRE, OVS_RELEASE, and OVS_HOLDS are suitable for use within macros,
  62  * where there is no function prototype to annotate. */
  63 #define OVS_ACQUIRES(MUTEX) __attribute__((context(MUTEX, 0, 1)))
  64 #define OVS_RELEASES(MUTEX) __attribute__((context(MUTEX, 1, 0)))
  65 #define OVS_MUST_HOLD(MUTEX) __attribute__((context(MUTEX, 1, 1)))
  66 #define OVS_ACQUIRE(MUTEX) __context__(MUTEX, 0, 1)
  67 #define OVS_RELEASE(MUTEX) __context__(MUTEX, 1, 0)
  68 #define OVS_HOLDS(MUTEX) __context__(MUTEX, 1, 1)
  69 #else
  70 #define OVS_ACQUIRES(MUTEX)
  71 #define OVS_RELEASES(MUTEX)
  72 #define OVS_MUST_HOLD(MUTEX)
  73 #define OVS_ACQUIRE(MUTEX)
  74 #define OVS_RELEASE(MUTEX)
  75 #define OVS_HOLDS(MUTEX)
  76 #endif
  77
  78 /* ISO C says that a C implementation may choose any integer type for an enum
  79  * that is sufficient to hold all of its values.  Common ABIs (such as the
  80  * System V ABI used on i386 GNU/Linux) always use a full-sized "int", even
  81  * when a smaller type would suffice.
  82  *
  83  * In GNU C, "enum __attribute__((packed)) name { ... }" defines 'name' as an
  84  * enum compatible with a type that is no bigger than necessary.  This is the
  85  * intended use of OVS_PACKED_ENUM.
  86  *
  87  * OVS_PACKED_ENUM is intended for use only as a space optimization, since it
  88  * only works with GCC.  That means that it must not be used in wire protocols
  89  * or otherwise exposed outside of a single process. */
  90 #if __GNUC__ && !__CHECKER__
  91 #define OVS_PACKED_ENUM __attribute__((__packed__))
  92 #else
  93 #define OVS_PACKED_ENUM
  94 #endif
  95
  96 #ifndef _MSC_VER
  97 #define OVS_PACKED(DECL) DECL __attribute__((__packed__))
  98 #else
  99 #define OVS_PACKED(DECL) __pragma(pack(push, 1)) DECL __pragma(pack(pop))
 100 #endif
 101
 102 #endif /* compiler.h */