SCons: Disable C++ exception handling

Upon investigating the extremely slow MSVC build times in #80513, I noticed
that while Godot policy is to never use exceptions, we weren't enforcing it
with compiler flags, and thus still included exception handling code and
stack unwinding.

This is wasteful on multiple aspects:

- Binary size: Around 20% binary size reduction with exceptions disabled
  for both MSVC and GCC binaries.
- Compile time:
  * More than 50% build time reduction with MSVC.
  * 10% to 25% build time reduction with GCC + LTO.
- Performance: Possibly, needs to be benchmarked.

Since users may want to re-enable exceptions in their own thirdparty code
or the libraries they compile with Godot, this behavior can be toggled with
the `disable_exceptions` SCons option, which defaults to true.

3 files changed, 5 insertions, 9 deletions

diff --git a/tests/SCsub b/tests/SCsub
index c59ce69b92..d96a1142e4 100644
--- a/tests/SCsub
+++ b/tests/SCsub
@@ -13,10 +13,8 @@ env_tests = env.Clone()
 if env_tests["platform"] == "windows":
     env_tests.Append(CPPDEFINES=[("DOCTEST_THREAD_LOCAL", "")])
 
-# Increase number of addressable sections in object files
-# due to doctest's heavy use of templates and macros.
-if env_tests.msvc:
-    env_tests.Append(CCFLAGS=["/bigobj"])
+if env["disable_exceptions"]:
+    env_tests.Append(CPPDEFINES=["DOCTEST_CONFIG_NO_EXCEPTIONS_BUT_WITH_ALL_ASSERTS"])
 
 env_tests.add_source_files(env.tests_sources, "*.cpp")
 
diff --git a/tests/core/io/test_image.h b/tests/core/io/test_image.h
index 92ab166ae8..1897971113 100644
--- a/tests/core/io/test_image.h
+++ b/tests/core/io/test_image.h
@@ -262,9 +262,7 @@ TEST_CASE("[Image] Modifying pixels of an image") {
 
 		for (const Rect2i &rect : rects) {
 			Ref<Image> img = memnew(Image(img_width, img_height, false, Image::FORMAT_RGBA8));
-			CHECK_NOTHROW_MESSAGE(
-					img->fill_rect(rect, Color(1, 1, 1, 1)),
-					"fill_rect() shouldn't throw for any rect.");
+			img->fill_rect(rect, Color(1, 1, 1, 1));
 			for (int y = 0; y < img->get_height(); y++) {
 				for (int x = 0; x < img->get_width(); x++) {
 					if (rect.abs().has_point(Point2(x, y))) {
@@ -317,7 +315,7 @@ TEST_CASE("[Image] Modifying pixels of an image") {
 	// Pre-multiply Alpha then Convert from RGBA to L8, checking alpha
 	{
 		Ref<Image> gray_image = memnew(Image(3, 3, false, Image::FORMAT_RGBA8));
-		CHECK_NOTHROW_MESSAGE(gray_image->fill_rect(Rect2i(0, 0, 3, 3), Color(1, 1, 1, 0)), "fill_rect() shouldn't throw for any rect.");
+		gray_image->fill_rect(Rect2i(0, 0, 3, 3), Color(1, 1, 1, 0));
 		gray_image->set_pixel(1, 1, Color(1, 1, 1, 1));
 		gray_image->set_pixel(1, 2, Color(0.5, 0.5, 0.5, 0.5));
 		gray_image->set_pixel(2, 1, Color(0.25, 0.05, 0.5, 1.0));
diff --git a/tests/scene/test_viewport.h b/tests/scene/test_viewport.h
index ab17459a41..dd4786977e 100644
--- a/tests/scene/test_viewport.h
+++ b/tests/scene/test_viewport.h
@@ -226,7 +226,7 @@ TEST_CASE("[SceneTree][Viewport] Controls and InputEvent handling") {
 
 	SUBCASE("[Viewport][GuiInputEvent] nullptr as argument doesn't lead to a crash.") {
 		ERR_PRINT_OFF;
-		CHECK_NOTHROW(root->push_input(nullptr));
+		root->push_input(nullptr);
 		ERR_PRINT_ON;
 	}