mfbt/Types.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /* mfbt foundational types and macros. */
   8
   9 #ifndef mozilla_Types_h
  10 #define mozilla_Types_h
  11
  12 /*
  13  * This header must be valid C and C++, includable by code embedding either
  14  * SpiderMonkey or Gecko.
  15  */
  16
  17 /* Expose all <stdint.h> types and size_t. */
  18 #include <stddef.h>
  19 #include <stdint.h>
  20
  21 /* Implement compiler and linker macros needed for APIs. */
  22
  23 /*
  24  * MOZ_EXPORT is used to declare and define a symbol or type which is externally
  25  * visible to users of the current library.  It encapsulates various decorations
  26  * needed to properly export the method's symbol.
  27  *
  28  *   api.h:
  29  *     extern MOZ_EXPORT int MeaningOfLife(void);
  30  *     extern MOZ_EXPORT int LuggageCombination;
  31  *
  32  *   api.c:
  33  *     int MeaningOfLife(void) { return 42; }
  34  *     int LuggageCombination = 12345;
  35  *
  36  * If you are merely sharing a method across files, just use plain |extern|.
  37  * These macros are designed for use by library interfaces -- not for normal
  38  * methods or data used cross-file.
  39  */
  40 #if defined(WIN32) || defined(XP_OS2)
  41 #  define MOZ_EXPORT   __declspec(dllexport)
  42 #else /* Unix */
  43 #  ifdef HAVE_VISIBILITY_ATTRIBUTE
  44 #    define MOZ_EXPORT       __attribute__((visibility("default")))
  45 #  elif defined(__SUNPRO_C) || defined(__SUNPRO_CC)
  46 #    define MOZ_EXPORT      __global
  47 #  else
  48 #    define MOZ_EXPORT /* nothing */
  49 #  endif
  50 #endif
  51
  52
  53 /*
  54  * Whereas implementers use MOZ_EXPORT to declare and define library symbols,
  55  * users use MOZ_IMPORT_API and MOZ_IMPORT_DATA to access them.  Most often the
  56  * implementer of the library will expose an API macro which expands to either
  57  * the export or import version of the macro, depending upon the compilation
  58  * mode.
  59  */
  60 #ifdef _WIN32
  61 #  if defined(__MWERKS__)
  62 #    define MOZ_IMPORT_API /* nothing */
  63 #  else
  64 #    define MOZ_IMPORT_API __declspec(dllimport)
  65 #  endif
  66 #elif defined(XP_OS2)
  67 #  define MOZ_IMPORT_API  __declspec(dllimport)
  68 #else
  69 #  define MOZ_IMPORT_API MOZ_EXPORT
  70 #endif
  71
  72 #if defined(_WIN32) && !defined(__MWERKS__)
  73 #  define MOZ_IMPORT_DATA  __declspec(dllimport)
  74 #elif defined(XP_OS2)
  75 #  define MOZ_IMPORT_DATA  __declspec(dllimport)
  76 #else
  77 #  define MOZ_IMPORT_DATA  MOZ_EXPORT
  78 #endif
  79
  80 /*
  81  * Consistent with the above comment, the MFBT_API and MFBT_DATA macros expose
  82  * export mfbt declarations when building mfbt, and they expose import mfbt
  83  * declarations when using mfbt.
  84  */
  85 #if defined(IMPL_MFBT)
  86 #  define MFBT_API     MOZ_EXPORT
  87 #  define MFBT_DATA    MOZ_EXPORT
  88 #else
  89   /*
  90    * On linux mozglue is linked in the program and we link libxul.so with
  91    * -z,defs. Normally that causes the linker to reject undefined references in
  92    * libxul.so, but as a loophole it allows undefined references to weak
  93    * symbols. We add the weak attribute to the import version of the MFBT API
  94    * macros to exploit this.
  95    */
  96 #  if defined(MOZ_GLUE_IN_PROGRAM)
  97 #    define MFBT_API   __attribute__((weak)) MOZ_IMPORT_API
  98 #    define MFBT_DATA  __attribute__((weak)) MOZ_IMPORT_DATA
  99 #  else
 100 #    define MFBT_API   MOZ_IMPORT_API
 101 #    define MFBT_DATA  MOZ_IMPORT_DATA
 102 #  endif
 103 #endif
 104
 105 /*
 106  * C symbols in C++ code must be declared immediately within |extern "C"|
 107  * blocks.  However, in C code, they need not be declared specially.  This
 108  * difference is abstracted behind the MOZ_BEGIN_EXTERN_C and MOZ_END_EXTERN_C
 109  * macros, so that the user need not know whether he is being used in C or C++
 110  * code.
 111  *
 112  *   MOZ_BEGIN_EXTERN_C
 113  *
 114  *   extern MOZ_EXPORT int MostRandomNumber(void);
 115  *   ...other declarations...
 116  *
 117  *   MOZ_END_EXTERN_C
 118  *
 119  * This said, it is preferable to just use |extern "C"| in C++ header files for
 120  * its greater clarity.
 121  */
 122 #ifdef __cplusplus
 123 #  define MOZ_BEGIN_EXTERN_C    extern "C" {
 124 #  define MOZ_END_EXTERN_C      }
 125 #else
 126 #  define MOZ_BEGIN_EXTERN_C
 127 #  define MOZ_END_EXTERN_C
 128 #endif
 129
 130 /*
 131  * GCC's typeof is available when decltype is not.
 132  */
 133 #if defined(__GNUC__) && defined(__cplusplus) && \
 134   !defined(__GXX_EXPERIMENTAL_CXX0X__) && __cplusplus < 201103L
 135 #  define decltype __typeof__
 136 #endif
 137
 138 #endif /* mozilla_Types_h */