Unable to recreate GDExtension instance with hot reloading enabled

[LouChiSoft]

Godot version

4.3-stable (Double precision)

godot-cpp version

4.3-stable (Double precision)

System information

Windows 10, R9 7900, RX 7900XT

Issue description

Debug compile for Windows 10, using CMake included via FetchContent and enabling hot reloading via GODOT_ENABLE_HOT_RELOAD set to ON or YES results in a Unable to recreate GDExtension instance - does this extension support hot reloading? error when rebuilding the project.

I've verified that the gdextension file has reloading enabled by adding a status message to the godot-cpp cmake file to print out the value of GODOT_ENABLE_HOT_RELOAD and make sure that it propagates from the top level which it does.

Steps to reproduce

• Clone this project: https://github.com/LouChiSoft/GDFlecs
• Optional: Add a status print to the godot-cpp CMakeLists.txt inside the build folder and print the value of GODOT_ENABLE_HOT_RELOAD from inside the CMakeLists to ensure that the value is set properly
• Configure with: cmake -B ./build -DPRECISION="double"
• Build with: cmake --build ./build --config Debug --parallel *desired thread count*
• Run with Godot 4.3.stable.double
• Make a code change and rebuild
• Make Godot the active window and Unable to recreate GDExtension instance - does this extension support hot reloading? should be in the output

Minimal reproduction project

https://github.com/LouChiSoft/GDFlecs

[LouChiSoft]

Hi, I was wondering if anyone had managed to have a look at this yet?

[dsnopek]

It sounds like HOT_RELOAD_ENABLED isn't defined when building your extension. I had thought the cmake configuration in the 4.3 branch did do that, but I haven't had a chance to double check

[LouChiSoft]

Is HOT_RELOAD_ENABLED different from GODOT_ENABLE_HOT_RELOAD? GODOT_ENABLE_HOT_RELOAD is the one in the comments at the top of the CMake file for Godot-cpp

[enetheru]

@LouChiSoft

in CMake:
GODOT_ENABLE_HOT_RELOAD is not a valid flag, and is not used anywhere.

GODOT_USE_HOT_RELOAD is the option for the cmake build, can be specified as part of the cmake configuration process like
cmake <path to source> -DGODOT_HOT_RELOAD=ON or added to your cmake scripts, or in a preset file, etc..

HOT_RELOAD_ENABLED is the cpp define added to the compiler command when compiling the extension, however it may not be the only thing needed to create a hot-reloadable library, for example gcc requires -fno-gnu-unique (After reviewing the build tools it appears to be the only other requirement).

In SCons the equivalent flag is use_hot_reload

[enetheru]

also, if the flag is not specified, then only the template_debug and editor builds define HOT_RELOAD_ENABLED