[cpp] attach CXXFLAGS to reduce the resource consumptions

Author: mysterywolf

components/libc/cplusplus/Kconfig

@@ -16,4 +16,8 @@ if RT_USING_CPLUSPLUS
         bool "Enable RT-Thread APIs C++ wrapper"
         default n
 
+    config RT_USING_CPP_REDUCE_OVERHEAD
+        bool "Disable exceptions to reduce overhead"
+        default n
+
 endif

components/libc/cplusplus/SConscript

@@ -5,8 +5,14 @@ Import('rtconfig')
 cwd     = GetCurrentDir()
 src     = ['cxx_crt_init.c', 'cxx_crt.cpp']
 CPPPATH = [cwd]
+CXXFLAGS = ''
 
-group = DefineGroup('CPP', src, depend=['RT_USING_CPLUSPLUS'], CPPPATH=CPPPATH)
+
+
+if GetDepend('RT_USING_CPP_REDUCE_OVERHEAD') and rtconfig.PLATFORM in ['gcc', 'armclang', 'llvm-arm']:
+    CXXFLAGS += ' -fno-exceptions -fno-rtti -ffunction-sections -fdata-sections -Wl,--gc-sections' # reduce resource consumptions
+
+group = DefineGroup('CPP', src, depend=['RT_USING_CPLUSPLUS'], CPPPATH=CPPPATH, CXXFLAGS=CXXFLAGS)
 
 list = os.listdir(cwd)
 for d in list:

components/libc/cplusplus/cpp11/gcc/__utils.h

@@ -17,11 +17,9 @@
 
 #include <rtthread.h>
 
-#define RT_USING_CPP_EXCEPTION
-
 inline void throw_system_error(int err, const char *what_msg)
 {
-#ifdef RT_USING_CPP_EXCEPTION
+#ifndef RT_USING_CPP_REDUCE_OVERHEAD
     throw std::system_error(std::error_code(err, std::system_category()), what_msg);
 #else
     (void)err;