src/lib/cc/compat_compiler.h

   1 /* Copyright (c) 2003-2004, Roger Dingledine
   2  * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   3  * Copyright (c) 2007-2019, The Tor Project, Inc. */
   4 /* See LICENSE for licensing information */
   5
   6 /**
   7  * \file compat_compiler.h
   8  * \brief Utility macros to handle different features and behavior in different
   9  *    compilers.
  10  **/
  11
  12 #ifndef TOR_COMPAT_COMPILER_H
  13 #define TOR_COMPAT_COMPILER_H
  14
  15 #include "orconfig.h"
  16 #include <inttypes.h>
  17
  18 #if defined(__has_feature)
  19 #  if __has_feature(address_sanitizer)
  20 /* Some of the fancy glibc strcmp() macros include references to memory that
  21  * clang rejects because it is off the end of a less-than-3. Clang hates this,
  22  * even though those references never actually happen. */
  23 #    undef strcmp
  24 #endif /* __has_feature(address_sanitizer) */
  25 #endif /* defined(__has_feature) */
  26
  27 #ifndef NULL_REP_IS_ZERO_BYTES
  28 #error "It seems your platform does not represent NULL as zero. We can't cope."
  29 #endif
  30
  31 #ifndef DOUBLE_0_REP_IS_ZERO_BYTES
  32 #error "It seems your platform does not represent 0.0 as zeros. We can't cope."
  33 #endif
  34
  35 #if 'a'!=97 || 'z'!=122 || 'A'!=65 || ' '!=32
  36 #error "It seems that you encode characters in something other than ASCII."
  37 #endif
  38
  39 /* GCC can check printf and scanf types on arbitrary functions. */
  40 #ifdef __GNUC__
  41 #define CHECK_PRINTF(formatIdx, firstArg) \
  42    __attribute__ ((format(printf, formatIdx, firstArg)))
  43 #else
  44 #define CHECK_PRINTF(formatIdx, firstArg)
  45 #endif /* defined(__GNUC__) */
  46 #ifdef __GNUC__
  47 #define CHECK_SCANF(formatIdx, firstArg) \
  48    __attribute__ ((format(scanf, formatIdx, firstArg)))
  49 #else
  50 #define CHECK_SCANF(formatIdx, firstArg)
  51 #endif /* defined(__GNUC__) */
  52
  53 /* What GCC do we have? */
  54 #ifdef __GNUC__
  55 #define GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
  56 #else
  57 #define GCC_VERSION 0
  58 #endif
  59
  60 /* Temporarily enable and disable warnings. */
  61 #ifdef __GNUC__
  62 #  define PRAGMA_STRINGIFY_(s) #s
  63 #  define PRAGMA_JOIN_STRINGIFY_(a,b) PRAGMA_STRINGIFY_(a ## b)
  64 /* Support for macro-generated pragmas (c99) */
  65 #  define PRAGMA_(x) _Pragma (#x)
  66 #  ifdef __clang__
  67 #    define PRAGMA_DIAGNOSTIC_(x) PRAGMA_(clang diagnostic x)
  68 #  else
  69 #    define PRAGMA_DIAGNOSTIC_(x) PRAGMA_(GCC diagnostic x)
  70 #  endif
  71 #  if defined(__clang__) || GCC_VERSION >= 406
  72 /* we have push/pop support */
  73 #    define DISABLE_GCC_WARNING(warningopt) \
  74           PRAGMA_DIAGNOSTIC_(push) \
  75           PRAGMA_DIAGNOSTIC_(ignored PRAGMA_JOIN_STRINGIFY_(-W,warningopt))
  76 #    define ENABLE_GCC_WARNING(warningopt) \
  77           PRAGMA_DIAGNOSTIC_(pop)
  78 #else /* !(defined(__clang__) || GCC_VERSION >= 406) */
  79 /* older version of gcc: no push/pop support. */
  80 #    define DISABLE_GCC_WARNING(warningopt) \
  81          PRAGMA_DIAGNOSTIC_(ignored PRAGMA_JOIN_STRINGIFY_(-W,warningopt))
  82 #    define ENABLE_GCC_WARNING(warningopt) \
  83          PRAGMA_DIAGNOSTIC_(warning PRAGMA_JOIN_STRINGIFY_(-W,warningopt))
  84 #endif /* defined(__clang__) || GCC_VERSION >= 406 */
  85 #else /* !(defined(__GNUC__)) */
  86 /* not gcc at all */
  87 # define DISABLE_GCC_WARNING(warning)
  88 # define ENABLE_GCC_WARNING(warning)
  89 #endif /* defined(__GNUC__) */
  90
  91 /* inline is __inline on windows. */
  92 #ifdef _WIN32
  93 #define inline __inline
  94 #endif
  95
  96 /* Try to get a reasonable __func__ substitute in place. */
  97 #if defined(_MSC_VER)
  98
  99 #define __func__ __FUNCTION__
 100
 101 #else
 102 /* For platforms where autoconf works, make sure __func__ is defined
 103  * sanely. */
 104 #ifndef HAVE_MACRO__func__
 105 #ifdef HAVE_MACRO__FUNCTION__
 106 #define __func__ __FUNCTION__
 107 #elif HAVE_MACRO__FUNC__
 108 #define __func__ __FUNC__
 109 #else
 110 #define __func__ "???"
 111 #endif /* defined(HAVE_MACRO__FUNCTION__) || ... */
 112 #endif /* !defined(HAVE_MACRO__func__) */
 113 #endif /* defined(_MSC_VER) */
 114
 115 #ifdef ENUM_VALS_ARE_SIGNED
 116 #define ENUM_BF(t) unsigned
 117 #else
 118 /** Wrapper for having a bitfield of an enumerated type. Where possible, we
 119  * just use the enumerated type (so the compiler can help us and notice
 120  * problems), but if enumerated types are unsigned, we must use unsigned,
 121  * so that the loss of precision doesn't make large values negative. */
 122 #define ENUM_BF(t) t
 123 #endif /* defined(ENUM_VALS_ARE_SIGNED) */
 124
 125 /* GCC has several useful attributes. */
 126 #if defined(__GNUC__) && __GNUC__ >= 3
 127 #define ATTR_NORETURN __attribute__((noreturn))
 128 #define ATTR_CONST __attribute__((const))
 129 #define ATTR_MALLOC __attribute__((malloc))
 130 #define ATTR_NORETURN __attribute__((noreturn))
 131 #define ATTR_WUR __attribute__((warn_unused_result))
 132 #define ATTR_UNUSED __attribute__ ((unused))
 133
 134 /** Macro: Evaluates to <b>exp</b> and hints the compiler that the value
 135  * of <b>exp</b> will probably be true.
 136  *
 137  * In other words, "if (PREDICT_LIKELY(foo))" is the same as "if (foo)",
 138  * except that it tells the compiler that the branch will be taken most of the
 139  * time.  This can generate slightly better code with some CPUs.
 140  */
 141 #define PREDICT_LIKELY(exp) __builtin_expect(!!(exp), 1)
 142 /** Macro: Evaluates to <b>exp</b> and hints the compiler that the value
 143  * of <b>exp</b> will probably be false.
 144  *
 145  * In other words, "if (PREDICT_UNLIKELY(foo))" is the same as "if (foo)",
 146  * except that it tells the compiler that the branch will usually not be
 147  * taken.  This can generate slightly better code with some CPUs.
 148  */
 149 #define PREDICT_UNLIKELY(exp) __builtin_expect(!!(exp), 0)
 150 #else /* !(defined(__GNUC__) && __GNUC__ >= 3) */
 151 #define ATTR_NORETURN
 152 #define ATTR_CONST
 153 #define ATTR_MALLOC
 154 #define ATTR_NORETURN
 155 #define ATTR_UNUSED
 156 #define ATTR_WUR
 157 #define PREDICT_LIKELY(exp) (exp)
 158 #define PREDICT_UNLIKELY(exp) (exp)
 159 #endif /* defined(__GNUC__) && __GNUC__ >= 3 */
 160
 161 /** Expands to a syntactically valid empty statement.  */
 162 #define STMT_NIL (void)0
 163
 164 /** Expands to a syntactically valid empty statement, explicitly (void)ing its
 165  * argument. */
 166 #define STMT_VOID(a) while (0) { (void)(a); }
 167
 168 #ifdef __GNUC__
 169 /** STMT_BEGIN and STMT_END are used to wrap blocks inside macros so that
 170  * the macro can be used as if it were a single C statement. */
 171 #define STMT_BEGIN (void) ({
 172 #define STMT_END })
 173 #elif defined(sun) || defined(__sun__)
 174 #define STMT_BEGIN if (1) {
 175 #define STMT_END } else STMT_NIL
 176 #else
 177 #define STMT_BEGIN do {
 178 #define STMT_END } while (0)
 179 #endif /* defined(__GNUC__) || ... */
 180
 181 /* Some tools (like coccinelle) don't like to see operators as macro
 182  * arguments. */
 183 #define OP_LT <
 184 #define OP_GT >
 185 #define OP_GE >=
 186 #define OP_LE <=
 187 #define OP_EQ ==
 188 #define OP_NE !=
 189
 190 #if defined(__MINGW32__) || defined(__MINGW64__)
 191 #define MINGW_ANY
 192 #endif
 193
 194 /** Macro: yield a pointer to the field at position <b>off</b> within the
 195  * structure <b>st</b>.  Example:
 196  * <pre>
 197  *   struct a { int foo; int bar; } x;
 198  *   off_t bar_offset = offsetof(struct a, bar);
 199  *   int *bar_p = STRUCT_VAR_P(&x, bar_offset);
 200  *   *bar_p = 3;
 201  * </pre>
 202  */
 203 #define STRUCT_VAR_P(st, off) ((void*) ( ((char*)(st)) + (off) ) )
 204
 205 /** Macro: yield a pointer to an enclosing structure given a pointer to
 206  * a substructure at offset <b>off</b>. Example:
 207  * <pre>
 208  *   struct base { ... };
 209  *   struct subtype { int x; struct base b; } x;
 210  *   struct base *bp = &x.base;
 211  *   struct *sp = SUBTYPE_P(bp, struct subtype, b);
 212  * </pre>
 213  */
 214 #define SUBTYPE_P(p, subtype, basemember) \
 215   ((void*) ( ((char*)(p)) - offsetof(subtype, basemember) ))
 216
 217 /** Macro: Yields the number of elements in array x. */
 218 #define ARRAY_LENGTH(x) ((sizeof(x)) / sizeof(x[0]))
 219
 220 #endif /* !defined(TOR_COMPAT_H) */