[NUC472/M453] Remove mbed_sdk_init_forced()

1. With mbed OS 5, mbed_sdk_init() is ensured to call before C++ global object constructor.
2. Refine startup file with GCC_ARM toolchain related to this modification.

Author: ccli8

targets/TARGET_NUVOTON/TARGET_M451/TARGET_NUMAKER_PFM_M453/mbed_overrides.c

@@ -16,14 +16,6 @@
 
 #include "analogin_api.h"
 
-// NOTE: Ensurce mbed_sdk_init() will get called before C++ global object constructor.
-#if defined(__CC_ARM) || defined(__GNUC__)
-void mbed_sdk_init_forced(void) __attribute__((constructor(101)));
-#elif defined(__ICCARM__)
-    // FIXME: How to achieve it in IAR?
-#endif
-
-
 void mbed_sdk_init(void)
 {
     // NOTE: Support singleton semantics to be called from other init functions
@@ -75,8 +67,3 @@ void mbed_sdk_init(void)
     /* Lock protected registers */
     SYS_LockReg();
 }
-
-void mbed_sdk_init_forced(void)
-{
-    mbed_sdk_init();
-}

targets/TARGET_NUVOTON/TARGET_M451/device/startup_M451Series.c

@@ -61,12 +61,11 @@ extern uint32_t __bss_start__;
 extern uint32_t __bss_end__;
 
 extern void uvisor_init(void);
-//#if defined(TOOLCHAIN_GCC_ARM)
-//extern void _start(void);
-//#endif
-extern void software_init_hook(void) __attribute__((weak));
-extern void __libc_init_array(void);
-extern int main(void);
+#if defined(TOOLCHAIN_GCC_ARM)
+extern void _start(void);
+#else
+#error("For GCC toolchain, only support GNU ARM Embedded")
+#endif
 #endif
 
 /* Default empty handler */
@@ -307,19 +306,8 @@ void Reset_Handler(void)
         }
     }
 
-    //uvisor_init();
+    _start();
 
-    if (software_init_hook) {
-        /**
-         * Give control to the RTOS via software_init_hook() which will also call __libc_init_array().
-         * Assume software_init_hook() is defined in libraries/rtos/rtx/TARGET_CORTEX_M/RTX_CM_lib.h.
-         */
-        software_init_hook();
-    }
-    else {
-        __libc_init_array();
-        main();
-    }
 #endif
 
     /* Infinite loop */

targets/TARGET_NUVOTON/TARGET_NUC472/TARGET_NUMAKER_PFM_NUC472/mbed_overrides.c

@@ -17,13 +17,6 @@
 #include "cmsis.h"
 #include "analogin_api.h"
 
-// NOTE: Ensurce mbed_sdk_init() will get called before C++ global object constructor.
-#if defined(__CC_ARM) || defined(__GNUC__)
-void mbed_sdk_init_forced(void) __attribute__((constructor(101)));
-#elif defined(__ICCARM__)
-    // FIXME: How to achieve it in IAR?
-#endif
-
 void mbed_sdk_init(void)
 {
     // NOTE: Support singleton semantics to be called from other init functions
@@ -88,8 +81,3 @@ void mbed_sdk_init(void)
     /* Lock protected registers */
     SYS_LockReg();
 }
-
-void mbed_sdk_init_forced(void)
-{
-    mbed_sdk_init();
-}

targets/TARGET_NUVOTON/TARGET_NUC472/device/startup_NUC472_442.c

@@ -63,12 +63,11 @@ extern uint32_t __bss_extern_start__  WEAK;
 extern uint32_t __bss_extern_end__ WEAK;
 
 extern void uvisor_init(void);
-//#if defined(TOOLCHAIN_GCC_ARM)
-//extern void _start(void);
-//#endif
-extern void software_init_hook(void) __attribute__((weak));
-extern void __libc_init_array(void);
-extern int main(void);
+#if defined(TOOLCHAIN_GCC_ARM)
+extern void _start(void);
+#else
+#error("For GCC toolchain, only support GNU ARM Embedded")
+#endif
 #endif
 
 /* Default empty handler */
@@ -476,19 +475,7 @@ void Reset_Handler(void)
         }
     }
 
-    //uvisor_init();
-
-    if (software_init_hook) {
-        /**
-         * Give control to the RTOS via software_init_hook() which will also call __libc_init_array().
-         * Assume software_init_hook() is defined in libraries/rtos/rtx/TARGET_CORTEX_M/RTX_CM_lib.h.
-         */
-        software_init_hook();
-    }
-    else {
-        __libc_init_array();
-        main();
-    }
+    _start();
 
 #endif
     /* Infinite loop */