added NORETURNs to functions that should not return

and added `UNREACHABLE();` to hint the compiler unreachable lines

added right signature for first parameter of `thread_stack_init()`
added `UNREACHABLE();` macro to `cpu/lpc1768/atom.c` and `cpu/msp430-common/cpu.c`

core/include/kernel_internal.h

@@ -20,6 +20,8 @@
 #ifndef KERNEL_INTERNAL_H_
 #define KERNEL_INTERNAL_H_
 
+#include "attributes.h"
+
 /**
  * @brief   Initializes scheduler and creates main and idle task
  */
@@ -44,7 +46,7 @@ char *thread_stack_init(void  (*task_func)(void), void *stack_start, int stack_s
 /**
  * @brief  Removes thread from scheduler and set status to #STATUS_STOPPED
  */
-void sched_task_exit(void);
+NORETURN void sched_task_exit(void);
 
 /**
  * @brief   Prints human readable, ps-like thread information for debugging purposes

core/include/sched.h

@@ -25,6 +25,7 @@
 #include <stddef.h>
 #include "bitarithm.h"
 #include "tcb.h"
+#include "attributes.h"
 
 #define MAXTHREADS 32 /**< the maximum number of threads to be scheduled */
 
@@ -65,7 +66,7 @@ void sched_switch(uint16_t current_prio, uint16_t other_prio);
 /**
  * @brief   Call context switching at thread exit
  */
-void cpu_switch_context_exit(void);
+NORETURN void cpu_switch_context_exit(void);
 
 /**
  * Flag indicating whether a context switch is necessary after handling an

core/sched.c

@@ -187,7 +187,7 @@ void sched_switch(uint16_t current_prio, uint16_t other_prio)
     }
 }
 
-void sched_task_exit(void)
+NORETURN void sched_task_exit(void)
 {
     DEBUG("sched_task_exit(): ending task %s...\n", active_thread->name);
 

cpu/lpc1768/atom.c

@@ -18,9 +18,9 @@
 #include "sched.h"
 #include "cpu.h"
 #include "irq.h"
+#include "kernel_internal.h"
 
-extern void sched_task_exit(void);
-void sched_task_return(void);
+NORETURN void sched_task_return(void);
 
 unsigned int atomic_set_return(unsigned int* p, unsigned int uiVal) {
 	//unsigned int cspr = disableIRQ();		//crashes
@@ -32,7 +32,7 @@ unsigned int atomic_set_return(unsigned int* p, unsigned int uiVal) {
 	return uiOldVal;
 }
 
-void cpu_switch_context_exit(void){
+NORETURN void cpu_switch_context_exit(void){
     sched_run();
     sched_task_return();
 }
@@ -78,7 +78,7 @@ void ctx_switch(void)
 	sched_task_return();
 }
 /* call scheduler so active_thread points to the next task */
-void sched_task_return(void)
+NORETURN void sched_task_return(void)
 {
 	/* load pdc->stackpointer in r0 */
 	asm("ldr     r0, =active_thread"); /* r0 = &active_thread */
@@ -89,6 +89,8 @@ void sched_task_return(void)
 	asm(" pop		{r0-r3,r12,lr}"); /* simulate register restor from stack */
 //	asm("pop 		{r4}"); /*foo*/
 	asm("pop		{pc}");
+
+    UNREACHABLE();
 }
 /*
  * cortex m4 knows stacks and handles register backups
@@ -109,7 +111,7 @@ void sched_task_return(void)
  *
  *
  */
-char * thread_stack_init(void * task_func, void * stack_start, int stack_size ) {
+char * thread_stack_init(void (*task_func)(void), void * stack_start, int stack_size ) {
 	unsigned int * stk;
 	stk = (unsigned int *) (stack_start + stack_size);
 

cpu/msp430-common/cpu.c

@@ -32,12 +32,14 @@ void thread_yield()
     __restore_context();
 }
 
-void cpu_switch_context_exit(void)
+NORETURN void cpu_switch_context_exit(void)
 {
     active_thread = sched_threads[0];
     sched_run();
 
     __restore_context();
+
+    UNREACHABLE();
 }
 
 /**