/GDNativeExample

Primary LanguageC

GDNativeExample

This is the official GDNative C example project from here (headers for Godot v3.3.stable from here), made to work as a CLion-compatible (CMakeLists.txt) project. It compiles and runs successfully under Windows.

CMakeLists.txt script:

cmake_minimum_required(VERSION 3.17)
project(GodotNeuralNetworkTests2)

set(CMAKE_CXX_STANDARD 14)
include_directories(${PROJECT_SOURCE_DIR}/godot-headers)
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ../project/gdnative/windows)

add_library(simple SHARED src/simple.c)

This does NOT work with the C++ version of GDNative, which requires SCons to generate the CPP bindings.

Library debugging from IDE

The IDE can also be made to run the game directly on debug by setting the following:

  • Executable to run: [path to Godot executable]
  • Working directory: <.../GDNativeExample/project/>

E.g. here's on my CLion settings: image

Library load/execution failure in Godot

For GDNative coding in general - there may be cases of the code perfectly compiling, but the library fails to load in the Godot project. This results in the infamous Error 126 ("The specified module could not be found") which gives back little to no information over the cause of the issue.

In the engine, it usually looks like failure on the load("res://<library_res_file_path>.gdns").new() line which throws the Attempt to call function 'new' in base 'NativeScript' on a null instance. error.

This error can be very annoying since it's very opaque and requires lots of trial and error to narrow down the culprit. From my experiments, I've found a couple of possible causes:

  • Failure to run godot_gdnative_init and/or registration of the library's class structure
  • Incorrect spelling of the class name (e.g. "Simple" instead of "SIMPLE" class_name field in the .gdns file)
  • Compiling the library init code as C++ instead of C (e.g. renaming "simple.c" to "simple.cpp")
  • Inclusion and usage of incompatible C++ mechanisms, like std::vector
  • Invalid externs which can be solved by using instead the following syntax: 
    #ifdef __cplusplus
#define CEXTERN extern "C"
#else
#define CEXTERN
#endif