The #GModule struct is an opaque data structure to represent a [dynamically-loaded module][glib-Dynamic-Loading-of-Modules]. It should only be accessed via the following functions. Closes a module. %TRUE on success a #GModule to close Ensures that a module will never be unloaded. Any future g_module_close() calls on the module will be ignored. a #GModule to make permanently resident Returns the filename that the module was opened with. If @module refers to the application itself, "main" is returned. the filename of the module a #GModule Gets a symbol pointer from a module, such as one exported by %G_MODULE_EXPORT. Note that a valid symbol can be %NULL. %TRUE on success a #GModule the name of the symbol to find returns the pointer to the symbol value A portable way to build the filename of a module. The platform-specific prefix and suffix are added to the filename, if needed, and the result is added to the directory, using the correct separator character. The directory should specify the directory where the module can be found. It can be %NULL or an empty string to indicate that the module is in a standard platform-specific directory, though this is not recommended since the wrong module may be found. For example, calling g_module_build_path() on a Linux system with a @directory of `/lib` and a @module_name of "mylibrary" will return `/lib/libmylibrary.so`. On a Windows system, using `\Windows` as the directory it will return `\Windows\mylibrary.dll`. the complete path of the module, including the standard library prefix and suffix. This should be freed when no longer needed the directory where the module is. This can be %NULL or the empty string to indicate that the standard platform-specific directories will be used, though that is not recommended the name of the module Gets a string describing the last module error. a string describing the last module error A thin wrapper function around g_module_open_full() a #GModule on success, or %NULL on failure the name of the file containing the module, or %NULL to obtain a #GModule representing the main program itself the flags used for opening the module. This can be the logical OR of any of the #GModuleFlags. Opens a module. If the module has already been opened, its reference count is incremented. First of all g_module_open_full() tries to open @file_name as a module. If that fails and @file_name has the ".la"-suffix (and is a libtool archive) it tries to open the corresponding module. If that fails and it doesn't have the proper module suffix for the platform (%G_MODULE_SUFFIX), this suffix will be appended and the corresponding module will be opened. If that fails and @file_name doesn't have the ".la"-suffix, this suffix is appended and g_module_open_full() tries to open the corresponding module. If eventually that fails as well, %NULL is returned. a #GModule on success, or %NULL on failure the name of the file containing the module, or %NULL to obtain a #GModule representing the main program itself the flags used for opening the module. This can be the logical OR of any of the #GModuleFlags Checks if modules are supported on the current platform. %TRUE if modules are supported Specifies the type of the module initialization function. If a module contains a function named g_module_check_init() it is called automatically when the module is loaded. It is passed the #GModule structure and should return %NULL on success or a string describing the initialization error. %NULL on success, or a string describing the initialization error the #GModule corresponding to the module which has just been loaded Errors returned by g_module_open_full(). there was an error loading or opening a module file a module returned an error from its `g_module_check_init()` function Flags passed to g_module_open(). Note that these flags are not supported on all platforms. specifies that symbols are only resolved when needed. The default action is to bind all symbols when the module is loaded. specifies that symbols in the module should not be added to the global name space. The default action on most platforms is to place symbols in the module in the global name space, which may cause conflicts with existing symbols. mask for all flags. Specifies the type of the module function called when it is unloaded. If a module contains a function named g_module_unload() it is called automatically when the module is unloaded. It is passed the #GModule structure. the #GModule about to be unloaded A portable way to build the filename of a module. The platform-specific prefix and suffix are added to the filename, if needed, and the result is added to the directory, using the correct separator character. The directory should specify the directory where the module can be found. It can be %NULL or an empty string to indicate that the module is in a standard platform-specific directory, though this is not recommended since the wrong module may be found. For example, calling g_module_build_path() on a Linux system with a @directory of `/lib` and a @module_name of "mylibrary" will return `/lib/libmylibrary.so`. On a Windows system, using `\Windows` as the directory it will return `\Windows\mylibrary.dll`. the complete path of the module, including the standard library prefix and suffix. This should be freed when no longer needed the directory where the module is. This can be %NULL or the empty string to indicate that the standard platform-specific directories will be used, though that is not recommended the name of the module Gets a string describing the last module error. a string describing the last module error Checks if modules are supported on the current platform. %TRUE if modules are supported These functions provide a portable way to dynamically load object files (commonly known as 'plug-ins'). The current implementation supports all systems that provide an implementation of dlopen() (e.g. Linux/Sun), as well as Windows platforms via DLLs. A program which wants to use these functions must be linked to the libraries output by the command `pkg-config --libs gmodule-2.0`. To use them you must first determine whether dynamic loading is supported on the platform by calling g_module_supported(). If it is, you can open a module with g_module_open(), find the module's symbols (e.g. function names) with g_module_symbol(), and later close the module with g_module_close(). g_module_name() will return the file name of a currently opened module. If any of the above functions fail, the error status can be found with g_module_error(). The #GModule implementation features reference counting for opened modules, and supports hook functions within a module which are called when the module is loaded and unloaded (see #GModuleCheckInit and #GModuleUnload). If your module introduces static data to common subsystems in the running program, e.g. through calling `g_quark_from_static_string ("my-module-stuff")`, it must ensure that it is never unloaded, by calling g_module_make_resident(). Example: Calling a function defined in a GModule |[<!-- language="C" --> // the function signature for 'say_hello' typedef void (* SayHelloFunc) (const char *message); gboolean just_say_hello (const char *filename, GError **error) { SayHelloFunc say_hello; GModule *module; module = g_module_open (filename, G_MODULE_BIND_LAZY); if (!module) { g_set_error (error, FOO_ERROR, FOO_ERROR_BLAH, "%s", g_module_error ()); return FALSE; } if (!g_module_symbol (module, "say_hello", (gpointer *)&say_hello)) { g_set_error (error, SAY_ERROR, SAY_ERROR_OPEN, "%s: %s", filename, g_module_error ()); if (!g_module_close (module)) g_warning ("%s: %s", filename, g_module_error ()); return FALSE; } if (say_hello == NULL) { g_set_error (error, SAY_ERROR, SAY_ERROR_OPEN, "symbol say_hello is NULL"); if (!g_module_close (module)) g_warning ("%s: %s", filename, g_module_error ()); return FALSE; } // call our function in the module say_hello ("Hello world!"); if (!g_module_close (module)) g_warning ("%s: %s", filename, g_module_error ()); return TRUE; } ]|