Error compiling GDExtension Demo - src\register_types.cpp(28): error C4430: missing type specifier

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:bust_in_silhouette: Asked By dcuny

I’m following the GDExtension tutorial, building on Windows 10, VS 2019.

At this point:

scons platform=windows

I get this error:

register_types.cpp
src\register_types.cpp(28): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
src\register_types.cpp(28): error C2143: syntax error: missing ',' before '*'
src\register_types.cpp(29): error C2065: 'p_interface': undeclared identifier
src\register_types.cpp(29): error C2065: 'p_library': undeclared identifier
src\register_types.cpp(29): error C2065: 'r_initialization': undeclared identifier
scons: *** [src\register_types.windows.template_debug.x86_64.obj] Error 2
scons: building terminated because of errors.

The source code is:

GDExtensionBool GDE_EXPORT example_library_init(const GDExtensionInterface *p_interface, const GDExtensionClassLibraryPtr p_library, GDExtensionInitialization *r_initialization) {
godot::GDExtensionBinding::InitObject init_obj(p_interface, p_library, r_initialization);

Since it’s complaining that it doesn’t recognize the type specifier, I assume that it’s not finding gdextension_interface.h, but the file exists and the definitions are there, such as:

...
typedef const void *GDExtensionMethodBindPtr;
typedef int64_t GDExtensionInt;
typedef uint8_t GDExtensionBool;
typedef uint64_t GDObjectInstanceID;
typedef void *GDExtensionRefPtr;
typedef const void *GDExtensionConstRefPtr;
...

But it appears that perhaps the path to the include file is broken?

I took a look at the SConstruct file, and it looks like

env.Dir("gdextension").abspath

is returning the correct path to gdextension_interface.h. So that’s not it.

dcuny | 2023-06-06 07:55

It looks like I might have a solution. gdextension_interface.h has the following comment:

Each GDExtension should define a C function that matches the signature 
of GDExtensionInitializationFunction, and export it so that it can be loaded via 
dlopen() or equivalent for the given platform.

For example:
 
GDExtensionBool my_extension_init(
    GDExtensionInterfaceGetProcAddress p_get_proc_address, 
    GDExtensionClassLibraryPtr p_library, 
    GDExtensionInitialization *r_initialization);

However, the signature of this function doesn’t match the one provided in the tutorial:

// Initialization.
GDExtensionBool GDE_EXPORT example_library_init(
  const GDExtensionInterface *p_interface, 
  const GDExtensionClassLibraryPtr p_library, 
  GDExtensionInitialization *r_initialization) {

    godot::GDExtensionBinding::InitObject init_obj(p_interface, p_library, r_initialization);

Changing it to this allows the code to compile (I haven’t tested execution yet, though):

// Initialization.
GDExtensionBool GDE_EXPORT example_library_init(
  const GDExtensionInterfaceGetProcAddress p_get_proc_address, 
  const GDExtensionClassLibraryPtr p_library, 
  GDExtensionInitialization *r_initialization) {

	godot::GDExtensionBinding::InitObject init_obj(p_get_proc_address, p_library, r_initialization);

dcuny | 2023-06-06 08:09

2
:bust_in_silhouette: Reply From: dcuny

Verified the documentation is incorrect and function parameter types have been changed. I found an example of register_types.cpp here:

GDE_EXPORT GDExtensionBool godot_init(
  const GDExtensionInterfaceGetProcAddress p_interface, 
  GDExtensionClassLibraryPtr p_library, 
  GDExtensionInitialization *r_initialization){

godot::GDExtensionBinding::InitObject init_obj(p_interface,p_library,r_initialization);
    ...

I’ll post a bug report on this.