Ported: 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.
- akien-mga
55550da68b

SConstruct

@@ -129,12 +129,12 @@ opts.Add(EnumVariable("optimize", "Optimization type", "speed", ("speed", "size"
 opts.Add(BoolVariable("production", "Set defaults to build Pandemonium for use in production", False))
 opts.Add(EnumVariable("lto", "Link-time optimization (production builds)", "none", ("none", "auto", "thin", "full")))
 opts.Add(BoolVariable("use_rtti", "Use RTTI", False))
-opts.Add(BoolVariable("use_exceptions", "Use exceptions", False))
 
 # Components
 opts.Add(BoolVariable("deprecated", "Enable deprecated features", True))
 opts.Add(BoolVariable("minizip", "Enable ZIP archive support using minizip", True))
 opts.Add(BoolVariable("xaudio2", "Enable the XAudio2 audio driver", False))
+opts.Add(BoolVariable("disable_exceptions", "Force disabling exception handling code", True))
 opts.Add("custom_modules", "A list of comma-separated directory paths containing custom modules to build.", "")
 opts.Add(BoolVariable("custom_modules_recursive", "Detect custom modules recursively for each specified path.", True))
 
@@ -475,36 +475,6 @@ if selected_platform in platform_list:
         env_base.Prepend(CPPDEFINES=["NO_SAFE_CAST"])
         env.Prepend(CPPDEFINES=["NO_SAFE_CAST"])
 
-    if not env_base["use_exceptions"]:
-        if not env.msvc:
-            env_base.Prepend(CXXFLAGS=["-fno-exceptions"])
-            env.Prepend(CXXFLAGS=["-fno-exceptions"])
-        else:
-            #env_base.Prepend(CXXFLAGS=["/EHa-"])
-            #env_base.Prepend(CXXFLAGS=["/EHs-"])
-            #env_base.Prepend(CXXFLAGS=["/EHc-"])
-            #not needed
-            #env_base.Prepend(CXXFLAGS=["/EHr-"])
-
-            #env.Prepend(CXXFLAGS=["/EHa-"])
-            #env.Prepend(CXXFLAGS=["/EHs-"])
-            #env.Prepend(CXXFLAGS=["/EHc-"])
-            #not needed
-            #env.Prepend(CXXFLAGS=["/EHr-"])
-
-            # Apparently disabling exceptions when you also need to have stl containers 
-            # (Some of the 3rd party code needs them)
-            # is not as simple with msvc as I originally thought.
-            # So for now they are always enabled.
-            # TODO: Write drop-in replacement for them. (They should use error macros, etc)
-            # (I bet it will come handy having them in more ways later.)
-            env_base.Prepend(CXXFLAGS=["/EHsc"])
-            env.Prepend(CXXFLAGS=["/EHsc"])
-    else:
-        if env.msvc:
-            env_base.Prepend(CXXFLAGS=["/EHsc"])
-            env.Prepend(CXXFLAGS=["/EHsc"])
-
     # Handle renamed options.
     if "use_lto" in ARGUMENTS or "use_thinlto" in ARGUMENTS:
         print("Error: The `use_lto` and `use_thinlto` boolean options have been unified to `lto=<none|thin|full>`.")
@@ -515,6 +485,16 @@ if selected_platform in platform_list:
         print("       Please adjust your scripts accordingly.")
         Exit(255)
 
+    # Disable exception handling. Godot doesn't use exceptions anywhere, and this
+    # saves around 20% of binary size and very significant build time (GH-80513).
+    if env["disable_exceptions"]:
+        if env.msvc:
+            env.Append(CPPDEFINES=[("_HAS_EXCEPTIONS", 0)])
+        else:
+            env.Append(CCFLAGS=["-fno-exceptions"])
+    elif env.msvc:
+        env.Append(CCFLAGS=["/EHsc"])
+
     # Configure compiler warnings
     if env.msvc:  # MSVC
         # Truncations, narrowing conversions, signed/unsigned comparisons...

platform/iphone/detect.py

@@ -34,7 +34,6 @@ def get_opts():
         ),
         ("IPHONESDK", "Path to the iPhone SDK", ""),
         BoolVariable("ios_simulator", "Build for iOS Simulator", False),
-        BoolVariable("ios_exceptions", "Enable exceptions", False),
         ("ios_triple", "Triple for ios toolchain", ""),
     ]
 
@@ -157,13 +156,6 @@ def configure(env):
         env.Append(CPPDEFINES=["NEED_LONG_INT"])
         env.Append(CPPDEFINES=["LIBYUV_DISABLE_NEON"])
 
-    # Disable exceptions on non-tools (template) builds
-    if not env["tools"]:
-        if env["ios_exceptions"]:
-            env.Append(CCFLAGS=["-fexceptions"])
-        else:
-            env.Append(CCFLAGS=["-fno-exceptions"])
-
     # Temp fix for ABS/MAX/MIN macros in iPhone SDK blocking compilation
     env.Append(CCFLAGS=["-Wno-ambiguous-macro"])
 

servers/audio_server.h

@@ -250,6 +250,11 @@ private:
 #ifdef DEBUG_ENABLED
 			uint64_t prof_time;
 #endif
+
+			Effect() {
+				enabled = false;
+				prof_time = 0;
+			}
 		};
 
 		Vector<Effect> effects;