--- a/src/proc.c	Wed Jun 19 17:28:28 2019 +0900
+++ b/src/proc.c	Wed Jun 19 17:53:14 2019 +0900
@@ -314,8 +314,10 @@
 
 int get_highest_priority_proc(void)
 {
-  int  highest_priority=ptable.proc->priority;
-  for(struct proc *p = ptable.proc; p < &ptable.proc[NPROC]; p++){
+  int highest_priority;
+   highest_priority=ptable.proc->priority;
+   struct proc *p;
+  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
     if(p->state != RUNNABLE) {
       continue;
     }   
@@ -338,7 +340,6 @@
 
 void scheduler(void)
 {
-    struct proc *p;
 
     for(;;){
         // Enable interrupts on this processor.
@@ -352,7 +353,8 @@
             // Switch to chosen process.  It is the process's job
             // to release ptable.lock and then reacquire it
             // before jumping back to us.
-	struct proc *p =ptable.proc[highest_priority];
+	struct proc *p; 
+          p=&ptable.proc[highest_priority];
             switchuvm(p);
          
             p->state = RUNNING;

--- a/src/syscall.c	Wed Jun 19 17:28:28 2019 +0900
+++ b/src/syscall.c	Wed Jun 19 17:53:14 2019 +0900
@@ -114,8 +114,8 @@
 extern int sys_wait(void);
 extern int sys_write(void);
 extern int sys_uptime(void);
-extern void sys_setpriority(void);
-
+extern int sys_setpriority(void);
+extern int getpriority(void);
 static int (*syscalls[])(void) = {
         [SYS_fork]    sys_fork,
         [SYS_exit]    sys_exit,

--- a/src/sysproc.c	Wed Jun 19 17:28:28 2019 +0900
+++ b/src/sysproc.c	Wed Jun 19 17:53:14 2019 +0900
@@ -94,15 +94,17 @@
 
     return xticks;
 }
-extern setpriority(int);
+extern void setpriority(int);
 
-void sys_setpriority(void)
+int sys_setpriority(void)
 { 
   int priority;
   if(argint(0, &priority) < 0) {
     return -1;
    }
   setpriority(priority);
+  return 0;
 }
 
 
+