[Core] Optionally delete Ref nullptr comparisons

Adds an optional (default true) compile option to enable comparing
`Ref` to `nullptr` to ensure correct use

.github/workflows/android_builds.yml

@@ -6,7 +6,7 @@ on:
 env:
   # Used for the cache key. Add version suffix to force clean build.
   GODOT_BASE_BRANCH: master
-  SCONSFLAGS: verbose=yes warnings=extra werror=yes debug_symbols=no module_text_server_fb_enabled=yes
+  SCONSFLAGS: verbose=yes warnings=extra werror=yes debug_symbols=no module_text_server_fb_enabled=yes ref_null_compare=no
 
 concurrency:
   group: ci-${{github.actor}}-${{github.head_ref || github.run_number}}-${{github.ref}}-android

.github/workflows/ios_builds.yml

@@ -6,7 +6,7 @@ on:
 env:
   # Used for the cache key. Add version suffix to force clean build.
   GODOT_BASE_BRANCH: master
-  SCONSFLAGS: verbose=yes warnings=extra werror=yes debug_symbols=no module_text_server_fb_enabled=yes
+  SCONSFLAGS: verbose=yes warnings=extra werror=yes debug_symbols=no module_text_server_fb_enabled=yes ref_null_compare=no
 
 concurrency:
   group: ci-${{github.actor}}-${{github.head_ref || github.run_number}}-${{github.ref}}-ios

.github/workflows/linux_builds.yml

@@ -6,7 +6,7 @@ on:
 env:
   # Used for the cache key. Add version suffix to force clean build.
   GODOT_BASE_BRANCH: master
-  SCONSFLAGS: verbose=yes warnings=extra werror=yes module_text_server_fb_enabled=yes
+  SCONSFLAGS: verbose=yes warnings=extra werror=yes module_text_server_fb_enabled=yes ref_null_compare=no
   DOTNET_NOLOGO: true
   DOTNET_CLI_TELEMETRY_OPTOUT: true
   TSAN_OPTIONS: suppressions=misc/error_suppressions/tsan.txt

.github/workflows/macos_builds.yml

@@ -6,7 +6,7 @@ on:
 env:
   # Used for the cache key. Add version suffix to force clean build.
   GODOT_BASE_BRANCH: master
-  SCONSFLAGS: verbose=yes warnings=extra werror=yes module_text_server_fb_enabled=yes
+  SCONSFLAGS: verbose=yes warnings=extra werror=yes module_text_server_fb_enabled=yes ref_null_compare=no
 
 concurrency:
   group: ci-${{github.actor}}-${{github.head_ref || github.run_number}}-${{github.ref}}-macos

.github/workflows/web_builds.yml

@@ -6,7 +6,7 @@ on:
 env:
   # Used for the cache key. Add version suffix to force clean build.
   GODOT_BASE_BRANCH: master
-  SCONSFLAGS: verbose=yes warnings=extra werror=yes debug_symbols=no use_closure_compiler=yes
+  SCONSFLAGS: verbose=yes warnings=extra werror=yes debug_symbols=no use_closure_compiler=yes ref_null_compare=no
   EM_VERSION: 3.1.64
   EM_CACHE_FOLDER: "emsdk-cache"
 

.github/workflows/windows_builds.yml

@@ -7,7 +7,7 @@ on:
 env:
   # Used for the cache key. Add version suffix to force clean build.
   GODOT_BASE_BRANCH: master
-  SCONSFLAGS: verbose=yes warnings=extra werror=yes module_text_server_fb_enabled=yes d3d12=yes "angle_libs=${{github.workspace}}/"
+  SCONSFLAGS: verbose=yes warnings=extra werror=yes module_text_server_fb_enabled=yes d3d12=yes ref_null_compare=no "angle_libs=${{github.workspace}}/"
   SCONS_CACHE_MSVC_CONFIG: true
 
 concurrency:

SConstruct

@@ -262,6 +262,7 @@ opts.Add(
     "",
 )
 opts.Add(BoolVariable("use_precise_math_checks", "Math checks use very precise epsilon (debug option)", False))
+opts.Add(BoolVariable("ref_null_compare", "Allows comparison between Ref and nullptr (debug option)", True))
 opts.Add(BoolVariable("scu_build", "Use single compilation unit build", False))
 opts.Add("scu_limit", "Max includes per SCU file when using scu_build (determines RAM use)", "0")
 opts.Add(BoolVariable("engine_update_check", "Enable engine update checks in the Project Manager", True))
@@ -518,6 +519,9 @@ if methods.get_cmdline_bool("fast_unsafe", env.dev_build):
 if env["use_precise_math_checks"]:
     env.Append(CPPDEFINES=["PRECISE_MATH_CHECKS"])
 
+if env["ref_null_compare"]:
+    env.Append(CPPDEFINES=["REF_NULL_COMPARE"])
+
 if env.editor_build:
     if env["engine_update_check"]:
         env.Append(CPPDEFINES=["ENGINE_UPDATE_CHECK_ENABLED"])

core/object/ref_counted.h

@@ -86,6 +86,11 @@ class Ref {
 	_FORCE_INLINE_ bool operator!=(const T *p_ptr) const {
 		return reference != p_ptr;
 	}
+#ifndef REF_NULL_COMPARE
+	// Delete these to prevent raw comparisons with `nullptr`.
+	bool operator==(std::nullptr_t) const = delete;
+	bool operator!=(std::nullptr_t) const = delete;
+#endif // REF_NULL_COMPARE
 
 	_FORCE_INLINE_ bool operator<(const Ref<T> &p_r) const {
 		return reference < p_r.reference;