mfbt/Types.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 /* mfbt foundational types and macros. */
   7
   8 #ifndef mozilla_Types_h_
   9 #define mozilla_Types_h_
  10
  11 /*
  12  * This header must be valid C and C++, includable by code embedding either
  13  * SpiderMonkey or Gecko.
  14  */
  15
  16 /*
  17  * Expose all the integer types defined in C99's <stdint.h> (and the integer
  18  * limit and constant macros, if compiling C code or if compiling C++ code and
  19  * the right __STDC_*_MACRO has been defined for each).  These are all usable
  20  * throughout mfbt code, and throughout Mozilla code more generally.
  21  */
  22 #include "mozilla/StandardInteger.h"
  23
  24 /* Also expose size_t. */
  25 #include <stddef.h>
  26
  27 /* Implement compiler and linker macros needed for APIs. */
  28
  29 /*
  30  * MOZ_EXPORT is used to declare and define a symbol or type which is externally
  31  * visible to users of the current library.  It encapsulates various decorations
  32  * needed to properly export the method's symbol.
  33  *
  34  *   api.h:
  35  *     extern MOZ_EXPORT int MeaningOfLife(void);
  36  *     extern MOZ_EXPORT int LuggageCombination;
  37  *
  38  *   api.c:
  39  *     int MeaningOfLife(void) { return 42; }
  40  *     int LuggageCombination = 12345;
  41  *
  42  * If you are merely sharing a method across files, just use plain |extern|.
  43  * These macros are designed for use by library interfaces -- not for normal
  44  * methods or data used cross-file.
  45  */
  46 #if defined(WIN32) || defined(XP_OS2)
  47 #  define MOZ_EXPORT   __declspec(dllexport)
  48 #else /* Unix */
  49 #  ifdef HAVE_VISIBILITY_ATTRIBUTE
  50 #    define MOZ_EXPORT       __attribute__((visibility("default")))
  51 #  elif defined(__SUNPRO_C) || defined(__SUNPRO_CC)
  52 #    define MOZ_EXPORT      __global
  53 #  else
  54 #    define MOZ_EXPORT /* nothing */
  55 #  endif
  56 #endif
  57
  58
  59 /*
  60  * Whereas implementers use MOZ_EXPORT to declare and define library symbols,
  61  * users use MOZ_IMPORT_API and MOZ_IMPORT_DATA to access them.  Most often the
  62  * implementer of the library will expose an API macro which expands to either
  63  * the export or import version of the macro, depending upon the compilation
  64  * mode.
  65  */
  66 #ifdef _WIN32
  67 #  if defined(__MWERKS__)
  68 #    define MOZ_IMPORT_API /* nothing */
  69 #  else
  70 #    define MOZ_IMPORT_API __declspec(dllimport)
  71 #  endif
  72 #elif defined(XP_OS2)
  73 #  define MOZ_IMPORT_API  __declspec(dllimport)
  74 #else
  75 #  define MOZ_IMPORT_API MOZ_EXPORT
  76 #endif
  77
  78 #if defined(_WIN32) && !defined(__MWERKS__)
  79 #  define MOZ_IMPORT_DATA  __declspec(dllimport)
  80 #elif defined(XP_OS2)
  81 #  define MOZ_IMPORT_DATA  __declspec(dllimport)
  82 #else
  83 #  define MOZ_IMPORT_DATA  MOZ_EXPORT
  84 #endif
  85
  86 /*
  87  * Consistent with the above comment, the MFBT_API and MFBT_DATA macros expose
  88  * export mfbt declarations when building mfbt, and they expose import mfbt
  89  * declarations when using mfbt.
  90  */
  91 #if defined(IMPL_MFBT)
  92 #  define MFBT_API     MOZ_EXPORT
  93 #  define MFBT_DATA    MOZ_EXPORT
  94 #else
  95   /*
  96    * On linux mozglue is linked in the program and we link libxul.so with
  97    * -z,defs. Normally that causes the linker to reject undefined references in
  98    * libxul.so, but as a loophole it allows undefined references to weak
  99    * symbols. We add the weak attribute to the import version of the MFBT API
 100    * macros to exploit this.
 101    */
 102 #  if defined(MOZ_GLUE_IN_PROGRAM)
 103 #    define MFBT_API   __attribute__((weak)) MOZ_IMPORT_API
 104 #    define MFBT_DATA  __attribute__((weak)) MOZ_IMPORT_DATA
 105 #  else
 106 #    define MFBT_API   MOZ_IMPORT_API
 107 #    define MFBT_DATA  MOZ_IMPORT_DATA
 108 #  endif
 109 #endif
 110
 111 /*
 112  * C symbols in C++ code must be declared immediately within |extern "C"|
 113  * blocks.  However, in C code, they need not be declared specially.  This
 114  * difference is abstracted behind the MOZ_BEGIN_EXTERN_C and MOZ_END_EXTERN_C
 115  * macros, so that the user need not know whether he is being used in C or C++
 116  * code.
 117  *
 118  *   MOZ_BEGIN_EXTERN_C
 119  *
 120  *   extern MOZ_EXPORT int MostRandomNumber(void);
 121  *   ...other declarations...
 122  *
 123  *   MOZ_END_EXTERN_C
 124  *
 125  * This said, it is preferable to just use |extern "C"| in C++ header files for
 126  * its greater clarity.
 127  */
 128 #ifdef __cplusplus
 129 #  define MOZ_BEGIN_EXTERN_C    extern "C" {
 130 #  define MOZ_END_EXTERN_C      }
 131 #else
 132 #  define MOZ_BEGIN_EXTERN_C
 133 #  define MOZ_END_EXTERN_C
 134 #endif
 135
 136 #endif  /* mozilla_Types_h_ */