ws_symbol_export.h

   1 /*
   2  * Cross platform defines for exporting symbols from shared libraries
   3  *
   4  * Wireshark - Network traffic analyzer
   5  * By Balint Reczey <balint@balintreczey.hu>
   6  * Copyright 2013 Balint Reczey
   7  *
   8  * SPDX-License-Identifier: GPL-2.0-or-later
   9  */
  10
  11 #include "ws_compiler_tests.h"
  12
  13 /** Reset symbol export behavior.
  14  * If you {un}define WS_BUILD_DLL on the fly you'll have to define this
  15  * as well.
  16  */
  17 #ifdef RESET_SYMBOL_EXPORT
  18
  19 #ifdef SYMBOL_EXPORT_H
  20 #undef SYMBOL_EXPORT_H
  21 #endif
  22
  23 #ifdef WS_DLL_PUBLIC
  24 #undef WS_DLL_PUBLIC
  25 #endif
  26
  27 #ifdef WS_DLL_PUBLIC_DEF
  28 #undef WS_DLL_PUBLIC_DEF
  29 #endif
  30
  31 #ifdef WS_DLL_LOCAL
  32 #undef WS_DLL_LOCAL
  33 #endif
  34
  35 #endif /* RESET_SYMBOL_EXPORT */
  36
  37 #ifndef SYMBOL_EXPORT_H
  38 #define SYMBOL_EXPORT_H
  39
  40 /*
  41  * NOTE: G_HAVE_GNUC_VISIBILITY is defined only if all of
  42  *
  43  *    __attribute__ ((visibility ("hidden")))
  44  *
  45  *    __attribute__ ((visibility ("internal")))
  46  *
  47  *    __attribute__ ((visibility ("protected")))
  48  *
  49  *    __attribute__ ((visibility ("default")))
  50  *
  51  * are supported, and at least some versions of GCC from Apple support
  52  * "default" and "hidden" but not "internal" or "protected", so it
  53  * shouldn't be used to determine whether "hidden" or "default" is
  54  * supported.
  55  *
  56  * This also means that we shouldn't use G_GNUC_INTERNAL instead of
  57  * WS_DLL_LOCAL, as GLib uses G_HAVE_GNUC_VISIBILITY to determine
  58  * whether to use __attribute__ ((visibility ("hidden"))) for
  59  * G_GNUC_INTERNAL, and that will not use it even with compilers
  60  * that support it.
  61  */
  62
  63 /* Originally copied from GCC Wiki at https://gcc.gnu.org/wiki/Visibility */
  64 #if defined _WIN32 || defined __CYGWIN__
  65   /* Compiling for Windows, so we use the Windows DLL declarations. */
  66   #ifdef WS_BUILD_DLL
  67     /*
  68      * Building a DLL; for all definitions, we want dllexport, and
  69      * (presumably so source from DLL and source from a program using the
  70      * DLL can both include a header that declares APIs and exported data
  71      * for the DLL), for declarations, either dllexport or dllimport will
  72      * work (they mean the same thing for a declaration when building a DLL).
  73      */
  74     #ifdef __GNUC__
  75       /* GCC */
  76       #define WS_DLL_PUBLIC_DEF __attribute__ ((dllexport))
  77     #else /* ! __GNUC__ */
  78       /*
  79        * Presumably MSVC.
  80        * Note: actually gcc seems to also support this syntax.
  81        */
  82       #define WS_DLL_PUBLIC_DEF __declspec(dllexport)
  83     #endif /* __GNUC__ */
  84   #else /* WS_BUILD_DLL */
  85     /*
  86      * Building a program; we should only see declarations, not definitions,
  87      * with WS_DLL_PUBLIC, and they all represent APIs or data imported
  88      * from a DLL, so use dllimport.
  89      *
  90      * For functions, export shouldn't be necessary; for data, it might
  91      * be necessary, e.g. if what's declared is an array whose size is
  92      * not given in the declaration.
  93      */
  94     #ifdef __GNUC__
  95       /* GCC */
  96       #define WS_DLL_PUBLIC_DEF __attribute__ ((dllimport))
  97     #elif ! (defined ENABLE_STATIC) /* ! __GNUC__ */
  98       /*
  99        * Presumably MSVC, and we're not building all-static.
 100        * Note: actually gcc seems to also support this syntax.
 101        */
 102       #define WS_DLL_PUBLIC_DEF __declspec(dllimport)
 103     #else /* ! __GNUC__  && ENABLE_STATIC */
 104       /*
 105        * Presumably MSVC, and we're building all-static, so we're
 106        * not building any DLLs.
 107        */
 108       #define WS_DLL_PUBLIC_DEF
 109     #endif /* __GNUC__ */
 110   #endif /* WS_BUILD_DLL */
 111
 112   /*
 113    * Symbols in a DLL are *not* exported unless they're specifically
 114    * flagged as exported, so, for a non-static but non-exported
 115    * symbol, we don't have to do anything.
 116    */
 117   #define WS_DLL_LOCAL
 118 #else /* defined _WIN32 || defined __CYGWIN__ */
 119   /*
 120    * Compiling for UN*X, where the dllimport and dllexport stuff
 121    * is neither necessary nor supported; just specify the
 122    * visibility if we have a compiler that supports doing so.
 123    */
 124   #if WS_IS_AT_LEAST_GNUC_VERSION(3,4) \
 125       || WS_IS_AT_LEAST_XL_C_VERSION(12,0)
 126     /*
 127      * GCC 3.4 or later, or some compiler asserting compatibility with
 128      * GCC 3.4 or later, or XL C 13.0 or later, so we have
 129      * __attribute__((visibility()).
 130      */
 131
 132     /*
 133      * Symbols exported from libraries.
 134      */
 135     #define WS_DLL_PUBLIC_DEF __attribute__ ((visibility ("default")))
 136
 137     /*
 138      * Non-static symbols *not* exported from libraries.
 139      */
 140     #define WS_DLL_LOCAL  __attribute__ ((visibility ("hidden")))
 141   #elif WS_IS_AT_LEAST_SUNC_VERSION(5,5)
 142     /*
 143      * Sun C 5.5 or later, so we have __global and __hidden.
 144      * (Sun C 5.9 and later also have __attribute__((visibility()),
 145      * but there's no reason to prefer it with Sun C.)
 146      */
 147
 148     /*
 149      * Symbols exported from libraries.
 150      */
 151     #define WS_DLL_PUBLIC_DEF __global
 152
 153     /*
 154      * Non-static symbols *not* exported from libraries.
 155      */
 156     #define WS_DLL_LOCAL __hidden
 157   #else
 158     /*
 159      * We have neither a way to make stuff not explicitly marked as
 160      * visible invisible outside a library nor a way to make stuff
 161      * explicitly marked as local invisible outside the library.
 162      */
 163
 164     /*
 165      * Symbols exported from libraries.
 166      */
 167     #define WS_DLL_PUBLIC_DEF
 168
 169     /*
 170      * Non-static symbols *not* exported from libraries.
 171      */
 172     #define WS_DLL_LOCAL
 173   #endif
 174 #endif
 175
 176 /*
 177  * You *must* use this for exported data *declarations*; if you use
 178  * WS_DLL_PUBLIC_DEF, some compilers, such as MSVC++, will complain
 179  * about array definitions with no size.
 180  *
 181  * You must *not* use this for exported data *definitions*, as that
 182  * will, for some compilers, cause warnings about items being initialized
 183  * and declared extern.
 184  *
 185  * Either can be used for exported *function* declarations and definitions.
 186  */
 187 #define WS_DLL_PUBLIC  WS_DLL_PUBLIC_DEF extern
 188
 189 #endif /* SYMBOL_EXPORT_H */
 190
 191 /*
 192  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 193  *
 194  * Local Variables:
 195  * c-basic-offset: 2
 196  * tab-width: 8
 197  * indent-tabs-mode: nil
 198  * End:
 199  *
 200  * vi: set shiftwidth=2 tabstop=8 expandtab:
 201  * :indentSize=2:tabSize=8:noTabs=true:
 202  */