141 lines
5 KiB
C
141 lines
5 KiB
C
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/**
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* PANDA 3D SOFTWARE
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* Copyright (c) Carnegie Mellon University. All rights reserved.
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*
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* All use of this software is subject to the terms of the revised BSD
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* license. You should have received a copy of this license along
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* with this source code in a file named "LICENSE."
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*
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* @file dtoolsymbols.h
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* @author drose
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* @date 2000-02-18
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*/
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#ifndef DTOOLSYMBOLS_H
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#define DTOOLSYMBOLS_H
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/*
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This file defines a slew of symbols that have particular meaning
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only when compiling in the WIN32 environment. These symbols are
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prefixed to each class declaration, and each global function, that
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is to be made visible outside of a DLL.
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The problem is that in Windows, you must prefix each DLL-public
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symbol with "__declspec(dllexport)" when you are compiling the DLL,
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but with "__declspec(dllimport)" when you are compiling code that
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links with the DLL. This strange convention means that you must, in
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principle, have two different .h files for a DLL: one to use for
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compiling the DLL (it must export all of the symbols), and a
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different one for presenting the public interface for other users to
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use (it must import all of the same symbols).
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In practice, of course, maintaining two different .h files is silly
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and error-prone; almost everyone solves this problem by defining a
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macro that evaluates to "__declspec(dllexport)" in one case and
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"__declspec(dllimport)" in another case. Many systems use the
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system macro _DLL to switch between these two case, which works well
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in a simple system because _DLL is defined only if compiler is
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currently generating code for a DLL. So you can export the symbols
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if _DLL is defined, and import them if it is not defined.
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However, this fails if you are compiling a DLL that wants to import
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symbols from another DLL, since in this case _DLL is defined, but
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the symbols in the other DLL need to be imported, not exported.
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In the general case of compiling multiple DLL's that might reference
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each other's symbols, we need have a separate macro for each DLL.
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Then when we are compiling code for each DLL, the macro for that
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particular DLL evaluates to "__declspec(dllexport)", exporting all
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the symbols from the DLL, while all the other DLL's macros evaluate
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to "__declspec(dllimport)", importing all the symbols from the other
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DLL's.
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That is the approach we have taken here in Panda. When we are
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compiling code for a particular DLL, the build scripts define the
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macro BUILDING_libname on the command line. This file then uses
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that macro to define EXPCL_libname appropriately for each DLL; this
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macro is then used to prefix each symbol to be exported from the
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DLL. The macro name stands for "export class", since it is used
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most often to mark a class for export, although the same macro can
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be used to export global functions. (We also define EXPTP_libname,
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which is used in conjunction with exporting template instantiations,
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another dicey task in Windows. It is used far less often.)
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Of course, this whole thing only matters under WIN32. In the rest
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of the world we don't have to deal with this nonsense, and so we
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can define all of these stupid symbols to the empty string.
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*/
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#ifdef BUILDING_DTOOL
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#define BUILDING_DTOOL_DTOOLBASE
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#define BUILDING_DTOOL_DTOOLUTIL
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#endif
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#ifdef BUILDING_DTOOLCONFIG
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#define BUILDING_DTOOL_PRC
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#define BUILDING_DTOOL_DCONFIG
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#endif
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#ifdef BUILDING_DTOOL_DTOOLBASE
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#define EXPCL_DTOOL_DTOOLBASE EXPORT_CLASS
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#define EXPTP_DTOOL_DTOOLBASE EXPORT_TEMPL
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#else
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#define EXPCL_DTOOL_DTOOLBASE IMPORT_CLASS
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#define EXPTP_DTOOL_DTOOLBASE IMPORT_TEMPL
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#endif
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#ifdef BUILDING_DTOOL_DTOOLUTIL
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#define EXPCL_DTOOL_DTOOLUTIL EXPORT_CLASS
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#define EXPTP_DTOOL_DTOOLUTIL EXPORT_TEMPL
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#else
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#define EXPCL_DTOOL_DTOOLUTIL IMPORT_CLASS
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#define EXPTP_DTOOL_DTOOLUTIL IMPORT_TEMPL
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#endif
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#ifdef BUILDING_DTOOL_PRC
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#define EXPCL_DTOOL_PRC EXPORT_CLASS
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#define EXPTP_DTOOL_PRC EXPORT_TEMPL
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#else
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#define EXPCL_DTOOL_PRC IMPORT_CLASS
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#define EXPTP_DTOOL_PRC IMPORT_TEMPL
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#endif
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#ifdef BUILDING_DTOOL_DCONFIG
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#define EXPCL_DTOOL_DCONFIG EXPORT_CLASS
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#define EXPTP_DTOOL_DCONFIG EXPORT_TEMPL
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#else
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#define EXPCL_DTOOL_DCONFIG IMPORT_CLASS
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#define EXPTP_DTOOL_DCONFIG IMPORT_TEMPL
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#endif
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#ifdef BUILDING_INTERROGATEDB
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#define EXPCL_INTERROGATEDB EXPORT_CLASS
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#define EXPTP_INTERROGATEDB EXPORT_TEMPL
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#else
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#define EXPCL_INTERROGATEDB IMPORT_CLASS
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#define EXPTP_INTERROGATEDB IMPORT_TEMPL
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#endif
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#ifdef BUILDING_MISC
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#define EXPCL_MISC EXPORT_CLASS
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#define EXPTP_MISC EXPORT_TEMPL
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#else /* BUILDING_MISC */
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#define EXPCL_MISC IMPORT_CLASS
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#define EXPTP_MISC IMPORT_TEMPL
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#endif /* BUILDING_MISC */
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/* These two are always defined empty, because pystub is statically
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built. But we leave the symbol around in case we change our minds
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to make pystub once again be a dynamic library. */
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#if __GNUC__ >= 4
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/* In GCC, though, we still need to mark the symbols as visible. */
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#define EXPCL_PYSTUB __attribute__((visibility("default")))
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#else
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#define EXPCL_PYSTUB
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#endif
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#define EXPTP_PYSTUB
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#endif
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