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Diffstat (limited to 'ACE/examples/Export/dll.h')
-rw-r--r-- | ACE/examples/Export/dll.h | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/ACE/examples/Export/dll.h b/ACE/examples/Export/dll.h new file mode 100644 index 00000000000..b07d3fe1cd8 --- /dev/null +++ b/ACE/examples/Export/dll.h @@ -0,0 +1,69 @@ +// $Id$ + +// To use the export macros with a DLL, a file will need to be +// created (see ACE_wrapper/bin/generate_export_file.pl) and +// included. This file defines Test_Export (and the +// TEST_SINGLETON_* macros). +#include "test_export.h" + +#include "ace/Singleton.h" +#include "ace/Null_Mutex.h" + +#define RETVAL 42 + +// To expose a function outside of a DLL, use the *_Export +// at the beginning of the function declaration. + +Test_Export int test_function (); + +// To expose data, put use the *Export at the beginning +// of the variable declaration. The extern is required when +// building static libraries. + +extern Test_Export int test_variable; + +// To expose a class, put the *_Export between "class" +// and the class name. + +class Test_Export test_class +{ +public: + int method (); +}; + +// ACE_Singleton and its relatives are special cases. The problem is +// that ACE_Singleton is a template. If the singleton is used in both +// the DLL and the executable linking the DLL, then two instances of +// the singleton will be used (which defeats the purpose of a Singleton). +// +// This occurs because the ACE_Singleton template is expanded in both +// places because Visual C++ and Borland C++ do this automatically by +// including the template source. This in turn creates two copies of +// the static member variable. +// +// So to get around this problem, the *_SINGLETON_DECLARE macro is +// used to instruct the compiler to not create the second copy in the +// program. This macro solution does not work for Borland C++, so for +// this compiler you must explicitly disable the template instantiation +// using a #pragma (or use the other workaround below). +// +// Another workaround for this is to not to expose the Singleton itself +// to the outside world, but to instead supply a function or static +// member function that returns the singleton to the executable +// (like get_dll_singleton () does below). + +#if defined (__BORLANDC__) +# if !defined (TEST_BUILD_DLL) +# pragma option push -Jgx +# endif +#endif +TEST_SINGLETON_DECLARE (ACE_Singleton, test_class, ACE_Null_Mutex) +#if defined (__BORLANDC__) +# if !defined (TEST_BUILD_DLL) +# pragma option pop +# endif +#endif + +typedef ACE_Singleton<test_class, ACE_Null_Mutex> TEST_SINGLETON; + +Test_Export test_class *get_dll_singleton (); |