include/ws_symbol_export.h

   1 /** @file
   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 ENABLE_STATIC
  95       /*
  96        * We're building all-static, so we're not building any DLLs.
  97        */
  98       #define WS_DLL_PUBLIC_DEF
  99     #elif defined(__GNUC__)
 100       /* GCC */
 101       #define WS_DLL_PUBLIC_DEF __attribute__ ((dllimport))
 102     #else /* ! ENABLE_STATIC && ! __GNUC__ */
 103       /*
 104        * Presumably MSVC, and we're not building all-static.
 105        * Note: actually gcc seems to also support this syntax.
 106        */
 107       #define WS_DLL_PUBLIC_DEF __declspec(dllimport)
 108     #endif
 109   #endif /* WS_BUILD_DLL */
 110
 111   /*
 112    * Symbols in a DLL are *not* exported unless they're specifically
 113    * flagged as exported, so, for a non-static but non-exported
 114    * symbol, we don't have to do anything.
 115    */
 116   #define WS_DLL_LOCAL
 117 #else /* defined _WIN32 || defined __CYGWIN__ */
 118   /*
 119    * Compiling for UN*X, where the dllimport and dllexport stuff
 120    * is neither necessary nor supported; just specify the
 121    * visibility if we have a compiler that supports doing so.
 122    */
 123   #if WS_IS_AT_LEAST_GNUC_VERSION(3,4) \
 124       || WS_IS_AT_LEAST_XL_C_VERSION(12,0)
 125     /*
 126      * GCC 3.4 or later, or some compiler asserting compatibility with
 127      * GCC 3.4 or later, or XL C 13.0 or later, so we have
 128      * __attribute__((visibility()).
 129      */
 130
 131     /*
 132      * Symbols exported from libraries.
 133      */
 134     #define WS_DLL_PUBLIC_DEF __attribute__ ((visibility ("default")))
 135
 136     /*
 137      * Non-static symbols *not* exported from libraries.
 138      */
 139     #define WS_DLL_LOCAL  __attribute__ ((visibility ("hidden")))
 140   #elif WS_IS_AT_LEAST_SUNC_VERSION(5,5)
 141     /*
 142      * Sun C 5.5 or later, so we have __global and __hidden.
 143      * (Sun C 5.9 and later also have __attribute__((visibility()),
 144      * but there's no reason to prefer it with Sun C.)
 145      */
 146
 147     /*
 148      * Symbols exported from libraries.
 149      */
 150     #define WS_DLL_PUBLIC_DEF __global
 151
 152     /*
 153      * Non-static symbols *not* exported from libraries.
 154      */
 155     #define WS_DLL_LOCAL __hidden
 156   #else
 157     /*
 158      * We have neither a way to make stuff not explicitly marked as
 159      * visible invisible outside a library nor a way to make stuff
 160      * explicitly marked as local invisible outside the library.
 161      */
 162
 163     /*
 164      * Symbols exported from libraries.
 165      */
 166     #define WS_DLL_PUBLIC_DEF
 167
 168     /*
 169      * Non-static symbols *not* exported from libraries.
 170      */
 171     #define WS_DLL_LOCAL
 172   #endif
 173 #endif
 174
 175 /*
 176  * You *must* use this for exported data *declarations*; if you use
 177  * WS_DLL_PUBLIC_DEF, some compilers, such as MSVC++, will complain
 178  * about array definitions with no size.
 179  *
 180  * You must *not* use this for exported data *definitions*, as that
 181  * will, for some compilers, cause warnings about items being initialized
 182  * and declared extern.
 183  *
 184  * Either can be used for exported *function* declarations and definitions.
 185  */
 186 #define WS_DLL_PUBLIC  WS_DLL_PUBLIC_DEF extern
 187
 188 /*
 189  * This is necessary to export symbols from wsutil to another DLL
 190  * (not an executable) using MSVC.
 191  */
 192 #ifdef _MSC_VER
 193 #  ifdef BUILD_WSUTIL
 194 #    define WSUTIL_EXPORT  __declspec(dllexport) extern
 195 #  else
 196 #    define WSUTIL_EXPORT  __declspec(dllimport) extern
 197 #  endif
 198 #else /* _MSC_VER */
 199 #  define WSUTIL_EXPORT    WS_DLL_PUBLIC
 200 #endif /* _MSC_VER */
 201
 202
 203
 204 #endif /* SYMBOL_EXPORT_H */
 205
 206 /*
 207  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 208  *
 209  * Local Variables:
 210  * c-basic-offset: 2
 211  * tab-width: 8
 212  * indent-tabs-mode: nil
 213  * End:
 214  *
 215  * vi: set shiftwidth=2 tabstop=8 expandtab:
 216  * :indentSize=2:tabSize=8:noTabs=true:
 217  */