Is this a C language undefined behaviour? Different results in clang and GCC

I'm getting different results for the same code with different compilers. Is this a undefined behaivour?

#include <stdio.h>
int a;
int b=10;
int puan_ekle(int puan, int bonus){
    puan=puan+bonus;
    a=puan-5;
    bonus--;
    return bonus;
}
int main(){
    a=23;
    printf("Result1 %d \n", a);
    a=a+puan_ekle(a,b);
    printf("Result2 %d \n", a);
    a=a+puan_ekle(a,b);
    printf("Result3 %d \n", a);
}