This lib is required to build Modules to be loaded with the Wii U Module System Loader.

A module needs to implements at least the following macros.

#include <wums.h>

WUMS_MODULE_EXPORT_NAME("homebrew_modulename");

WUMS_INITIALIZE() {
    /** THIS CODE WILL BE RUN ONCE **/ 
}

The WUMS_MODULE_EXPORT_NAME needs to be a globally unique name across all loaded modules. WUMS_INITIALIZE defines the code that will be run after the module was loaded. The module will have full permission to the sd card via fs:/vol/external01.

Other optional macros/hooks are support, here some examples:

WUMS_APPLICATION_STARTS() {
    /** Is called when a new application was started. **/
}

WUMS_APPLICATION_REQUESTS_EXIT() {
    /** Is called when a new application is going to be closed. **/
}

This list is incomplete, see hooks.h for all hooks and meta.h for all macros.

Modules can be used to export functions for other modules or "normal" applications.

#include <wums.h>

void MyCustomFunction() {
    /** Some special code that should be useable for everyone */
}

WUMS_EXPORT_FUNCTION(MyCustomFunction);

This function can then be used like they would be inside a .rpl, where the name of the "rpl" is the one defined in WUMS_MODULE_EXPORT_NAME.

Example using the Cafe OS OSDynLoad API:

if (OSDynLoad_Acquire("homebrew_modulename", &sModuleHandle) != OS_DYNLOAD_OK) {
    OSFatal("OSDynLoad_Acquire failed.");
}

void (*sMyCustomFunction)() = NULL;

if (OSDynLoad_FindExport(sModuleHandle, FALSE, "MyCustomFunction", (void**) &sMyCustomFunction) != OS_DYNLOAD_OK) {
    OSFatal("OSDynLoad_FindExport failed.");
}

A prebuilt version of this lib can found on dockerhub. To use it for your projects, add this to your Dockerfile.

[...]
COPY --from=wiiuenv/wiiumodulesystem:[tag] /artifacts $DEVKITPRO
[...]

Replace [tag] with a tag you want to use, a list of tags can be found here. It's highly recommended to pin the version to the latest date instead of using latest.

docker run --rm -v ${PWD}:/src wiiuenv/clang-format:13.0.0-2 -r ./include ./libraries ./example/example_module/source -i