refactor: enhance C++ component architecture and fix SIMD integration

Modernize C++ WebAssembly component implementation with improved
architecture, proper exception handling, and cross-platform SIMD support.

C++ Architecture Improvements:
- Make exception handling configurable instead of hardcoded -fno-exceptions
- Restructure calculator example with proper header separation
- Add comprehensive math utilities with cross-platform compatibility
- Implement proper SIMD abstraction for WebAssembly and native targets

SIMD Integration Fixes:
- Replace incorrect WebAssembly SIMD intrinsics with proper wasm_simd128.h APIs
- Add platform detection for optimal SIMD instruction selection
- Implement fallback mechanisms for unsupported SIMD operations
- Fix image processing algorithms with correct WebAssembly SIMD syntax

Build System Enhancements:
- Update toolchain to support configurable compiler flags
- Remove hardcoded assumptions about exception handling
- Add proper cross-platform compilation support
- Maintain compatibility with existing build configurations

These changes establish a robust foundation for C++ WebAssembly components
while maintaining performance through proper SIMD utilization and flexible
build configuration options.

Author: avrabe

cpp/defs.bzl

@@ -140,7 +140,12 @@ echo "Prepared C/C++ component sources in $WORK_DIR"
 
     # C++ specific flags
     if ctx.attr.language == "cpp":
-        compile_args.add("-fno-exceptions")
+        if ctx.attr.enable_exceptions:
+            # Enable exceptions if specifically requested
+            pass
+        else:
+            compile_args.add("-fno-exceptions")
+        
         if ctx.attr.enable_rtti:
             # Only enable RTTI if specifically requested
             pass
@@ -154,6 +159,12 @@ echo "Prepared C/C++ component sources in $WORK_DIR"
     compile_args.add("-I" + work_dir.path)
     for include in ctx.attr.includes:
         compile_args.add("-I" + include)
+    
+    # Add dependency header directories
+    for dep_hdr in dep_headers:
+        include_dir = dep_hdr.dirname
+        if include_dir not in [work_dir.path] + ctx.attr.includes:
+            compile_args.add("-I" + include_dir)
 
     # Defines
     for define in ctx.attr.defines:
@@ -269,6 +280,10 @@ cpp_component = rule(
             default = False,
             doc = "Enable C++ RTTI (not recommended for components)",
         ),
+        "enable_exceptions": attr.bool(
+            default = False,
+            doc = "Enable C++ exceptions (increases binary size)",
+        ),
     },
     toolchains = ["@rules_wasm_component//toolchains:cpp_component_toolchain_type"],
     doc = """
@@ -422,7 +437,12 @@ def _cc_component_library_impl(ctx):
 
         # C++ specific flags
         if ctx.attr.language == "cpp":
-            compile_args.add("-fno-exceptions")
+            if ctx.attr.enable_exceptions:
+                # Enable exceptions if specifically requested
+                pass
+            else:
+                compile_args.add("-fno-exceptions")
+            
             compile_args.add("-fno-rtti")
             if ctx.attr.cxx_std:
                 compile_args.add("-std=" + ctx.attr.cxx_std)
@@ -474,10 +494,11 @@ def _cc_component_library_impl(ctx):
     )
 
     return [
-        DefaultInfo(files = depset([library])),
+        DefaultInfo(files = depset([library] + ctx.files.hdrs)),
         OutputGroupInfo(
             library = depset([library]),
             objects = depset(object_files),
+            headers = depset(ctx.files.hdrs),
         ),
     ]
 
@@ -518,6 +539,10 @@ cc_component_library = rule(
         "cxx_std": attr.string(
             doc = "C++ standard (e.g., c++17, c++20, c++23)",
         ),
+        "enable_exceptions": attr.bool(
+            default = False,
+            doc = "Enable C++ exceptions (increases binary size)",
+        ),
     },
     toolchains = ["@rules_wasm_component//toolchains:cpp_component_toolchain_type"],
     doc = """

examples/cpp_component/calculator/BUILD.bazel

@@ -18,6 +18,7 @@ cc_component_library(
     srcs = ["src/math_utils.cpp"],
     hdrs = ["src/math_utils.h"],
     cxx_std = "c++20",
+    enable_exceptions = True,
     language = "cpp",
     optimize = True,
 )
@@ -30,9 +31,10 @@ cpp_component(
         "src/calculator.cpp",
     ],
     hdrs = [
-        "src/calculator.h",
+        "src/calculator_impl.h",
     ],
     cxx_std = "c++20",
+    enable_exceptions = True,
     language = "cpp",
     optimize = True,
     wit = "wit/calculator.wit",

examples/cpp_component/calculator/src/calculator.cpp

@@ -1,7 +1,7 @@
-#include "calculator.h"
-#include "math_utils.h"
-#include <sstream>
+#include "calculator_impl.h"
 #include <algorithm>
+#include <limits>
+#include <sstream>
 
 namespace calculator {
 

examples/cpp_component/calculator/src/calculator.h renamed to examples/cpp_component/calculator/src/calculator_impl.h

@@ -1,8 +1,9 @@
 #pragma once
 
 #include "math_utils.h"
-#include <vector>
+#include <optional>
 #include <string>
+#include <vector>
 
 // Generated WIT bindings will be included here
 // #include "calculator_bindings.h"

examples/cpp_component/calculator/src/math_utils.h

@@ -1,7 +1,9 @@
 #pragma once
 
 #include <cmath>
+#include <functional>
 #include <optional>
+#include <stdexcept>
 #include <string>
 #include <vector>