Extension registry

Beyond the automatic discovery of arcdps_*.dll files at startup (described in Getting Started), arcdps exposes a small runtime API for loading, unloading, and enumerating extensions programmatically — used by chainloaders and multi-module extension managers. It also exports a couple of exception/update-related utility functions with less certain documentation status.

Descriptions for addextension2, removeextension2, and listextension are sourced from the official arcdps API reference (https://www.deltaconnected.com/arcdps/api/README.txt). c_closeandupdate and c_exceptionerrormsg are not described in that document — their sections below are reconstructed from binary evidence (strings in arcdps build 1.2026.718.905) and labeled as such.

One naming note for readers of community bindings: the Rust arcdps-rs bindings expose removeextension2 under the name freeextension2 — the actual export in arcdps’ table is removeextension2.

addextension2 — load an extension

uint32_t addextension2(HINSTANCE hinst);

Loads an extension. arcdps will LoadLibrary the given HINSTANCE to increment its refcount, call its get_init_addr, and call the function it returns — the same load sequence used for extensions discovered automatically at startup (see Getting Started).

Return value is 0 on success, or non-zero on error, per enum n_arcdpsextensionload. (The official notes give the parameter as HINSTANCE hinst and describe the return only in prose; the uint32_t return type above is inferred from it being a small status code.)

/* arcdps api extension load result */
enum n_arcdpsextensionload {
    ARCDPSEXTENLOAD_OK,
    ARCDPSEXTENLOAD_NO_SIG,
    ARCDPSEXTENLOAD_INVALID_IMGUI, // extension stays loaded with imgui functions disabled
    ARCDPSEXTENLOAD_OBSOLETE,
    ARCDPSEXTENLOAD_ALREADY_LOADED,
    ARCDPSEXTENLOAD_NO_FUNCTION_TABLE_RETURNED,
    ARCDPSEXTENLOAD_NO_INIT_FUNCTION_RETURNED,
    ARCDPSEXTENLOAD_LOADLIBRARY_ERROR,
    ARCDPSEXTENLOAD_NO_SLOTS_LEFT,
    ARCDPSEXTENLOAD_MISSING_GET_RELEASE_ADDR,
    ARCDPSEXTENLOAD_SHUTDOWN,
    ARCDPSEXTENLOAD_REMOVE_VIA_EXPORT,
};

removeextension2 — remove an extension

HINSTANCE removeextension2(uint32_t sig);

Removes an extension identified by sig (the same sig value the extension set on its arcdps_exports table — see Getting Started). arcdps will FreeLibrary the module, call its get_release_addr, and call the function it returns.

Upon returning from removal, there will be no more pending callbacks; however, the caller must ensure no callbacks are executing before freeing the module.

Return value is 0 if the module was not found, or the HINSTANCE of the DLL otherwise.

listextension — enumerate loaded extensions

void listextension(void* callback_fn);

Callback-driven listing of currently loaded extensions. callback_fn is of type:

void callback_fn(arcdps_exports* exp);

The callback is invoked once for each extension currently loaded, with a pointer to that extension’s arcdps_exports table (the same struct shape described in Getting Started).

c_closeandupdate — rundll32 self-update entry point

Not described in the official arcdps API reference — but the arcdps binary itself (build 1.2026.718.905) reveals how it’s used. The DLL contains this command-line template:

rundll32.exe "%s",c_closeandupdate "%lu,%s"

i.e. arcdps re-invokes itself through rundll32.exe, calling this export in a fresh process to swap in a downloaded update after the game closes. Surrounding strings confirm the workflow: staged *.dll_update files, “failed to find arcdps dll_update file, update aborted”, “multiple arcdps modules detected, update aborted”, and “failed to find arcdps in process module list”. The signature is therefore the standard rundll32 entry convention (void CALLBACK fn(HWND, HINSTANCE, LPSTR cmdline, int)), with the "%lu,%s" argument string carrying a process id and path.

This is an internal updater mechanism, not extension-facing API — don’t call it. (Classification is binary evidence, not official documentation.)

c_exceptionerrormsg — rundll32 crash-dialog entry point

Also undocumented officially; also resolved by binary evidence. The DLL contains:

rundll32.exe "%s",c_exceptionerrormsg "%s"

used alongside the crash-handler strings (“Intercepted unhandled exception in GW2 process. Game will terminate when this box is closed”) — arcdps spawns itself via rundll32 to display the crash dialog from outside the dying game process, with the message text as the argument. Same rundll32 entry convention; same caveat: internal, not extension-facing.