Question

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How to find the sizeof(a pointer pointing to an array)
Sizeof an array in the C programming language?

#include<stdio.h>

void doit(char x[10]){
    printf("%d\n", sizeof(x));
}

void main(void){
    char x[10];
    printf("%d\n", sizeof(x));
    doit(x);
}

** I don’t know why my question is removed first time. **
Two outputs here are different. Apparently the first one knows x is an array and second one only knows it a ptr. My question is why compiler knows that in the first case it’s an array instead of a ptr?

Answer 1

I am no compiler expert but during the compilation phase, the compiler performs something called semantic analysis. During this phase, type checking is done. sizeof is also a compile time operator ( barring VLArrays probably ) and during type checking the compiler determines that in main, x is an array and in doit function it is a pointer.

Its like, the compiler is the owner of the house and hence it knows the type of its tenants.

Read about the compilation process on wiki