GDExtension reload spam on Windows 10 due to inconsistent last_modified_time handling

[kkolyan]

Godot version

v4.2.dev (0ca8542)

System information

Godot v4.2.dev (0ca8542) - Windows 10.0.19042 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1660 Ti (NVIDIA; 31.0.15.3713) - Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz (12 Threads)

Issue description

Context: godot-rust/gdext hot reload support.

The root cause of the problem is last_modified_time is updated using original DLL file, but checked using DLL copy (that is really loaded).

library_path is checked:

godot/core/extension/gdextension.cpp

Line 976 in 0ca8542

if (FileAccess::get_modified_time(library_path) > last_modified_time) {

library_path is initialized by loaded DLL path:

godot/core/extension/gdextension.cpp

Line 686 in 0ca8542

Error err = OS::get_singleton()->open_dynamic_library(p_path, library, true, &library_path);

library path is updated using original DLL modification time:

godot/core/extension/gdextension.cpp

Line 883 in 0ca8542

FileAccess::get_modified_time(library_path),

From debug inside GDExtension::has_library_changed:

FileAccess::get_modified_time(String::utf8("res://rust/target/debug/fmandate.dll", 36)) = {unsigned long long} 1696116779
FileAccess::get_modified_time(library_path) = {unsigned long long} 									1696117721
FileAccess::get_modified_time(get_path()) = {unsigned long long} 									1696099045
last_modified_time = {unsigned long long} 														1696116779
library_path = U"C:\dev\godot\fmandate-gd\rust\target\debug\~fmandate.dll"

Steps to reproduce

1. checkout godot master branch
2. compile it with scons dev_build=yes debug_symbols=yes platform=windows compiledb=yes -j8
3. get some gdextension. dodge-the-creeps example from gdext is fine, then git clone https://github.com/godot-rust/gdext.git && cd gdext/examples/dodge-the-creeps/rust
4. compile this gdextension cargo build --package dodge-the-creeps --lib
5. place breakpoint inside GDExtensionManager::reload_extension
6. start editor with debugger (I used CLion) path_to_godot_working_copy\bin\godot.windows.editor.x86_64.exe --editor --path ../godot (that's path from rust dir to gdext/examples/dodge-the-creeps/godot)
7. wait for scene loading. it should load fine.
8. alt+tab somewhere
9. catch breakpoint
10. repeat 8-9 infinitely

Minimal reproduction project

N/A