Question

here is my code.

#include <stdio.h>
#define MAX(a,b) ((a)>(b)?(a):(b))
#define SZA(a) (sizeof(a)/sizeof(a[0]))

int anish=0; // global variable showing abrupt behaviour
int a[]={0,1,5,8,9,10,17,17,20,24,30};
int n= SZA(a);

int cache[100];
int road(int len)
{
    anish++;

    if(cache[len]!=-1)
        return cache[len];
    if(len<=0)
        return 0;
    int max=0;
    int i;
    for(i=1;(i<n && len>=i);i++)
    {
        max=MAX(max,a[i]+road(len-i));
    }
    return cache[len]=max;
}

void f()
{
    anish=13;
}

int main()
{
    int i;
    for(i=0;i<=13;i++)
        cache[i]=-1;
    int len=10;
    // f();

    printf("%d %d\n",road(len),anish);
    return 0;
}

In this, road() is a recursive function and I want to calculate the number of times this function is being executed. So, I am doing this via a global variable anish.
But the value of anish is not changing in this road() function, while in function f() value of anish is being modified.

Any reason for this absurd behavior?

Answer 1

your c code shows an outdated anish variable
succesive printf’s shows different value

this has something to do with c’s internals

it has something to do with this : Parameter evaluation order before a function calling in C

loki astari said:

The order that function parameters are evaluated is unspecified
behavior. (This won’t make your program crash, explode, or order
pizza… unlike undefined behavior.)

The only requirement is that all parameters must be fully evaluated
before the function is called.