CODEWITHSUNDEEP
c
sind
sind

Reputation: 41

Why am I not getting an error when re-declaring a variable?

#include<stdio.h>
int x;
int main()
{
    int x;
    return 0;
}

Why am I not getting an error, even though I am re-declaring the variable x with the same name?

Upvotes: 0

Views: 82

Answers (2)

RKou
RKou

Reputation: 5221

It is allowed although not advised to define variables with the same names provided that they are not in the same scope. Inside the main() function, the x in the local scope has more precedence than x in the global scope.

But it is confusing and error prone to define variables with the same names. With a compiler like gcc, you can activate some options to track them. For example, the "-Wshadow" will warn you that x in main() shadows the global variable with the same name:

$ gcc try.c -Wshadow
try.c: In function ‘main’:
try.c:5:5: warning: declaration of ‘x’ shadows a global declaration [-Wshadow]
 int x;
     ^
try.c:2:5: note: shadowed declaration is here
 int x;
     ^

Upvotes: 3

Nassim Gadhi
Nassim Gadhi

Reputation: 173

To expand on what Some programmer dude said in the comment,

A scope is a region of the program and broadly speaking there are three places, where variables can be declared −

  • Inside a function or a block which is called local variables,

  • In the definition of function parameters which is called formal parameters.

  • Outside of all functions which is called global variables.

The int x above your main is a global variable which can be used by any function inside your program.

The int x inside your main is a local variable and can only be used logically inside your main.

Check out this link for more info. https://www.tutorialspoint.com/cplusplus/cpp_variable_scope.htm

Upvotes: 4

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