Redeclaration of global variable in C

• Difficulty Level : Easy
• Last Updated : 28 May, 2017

Consider the below two programs:

// Program 1

int main()

{

   int x;

   int x = 5;

   printf("%d", x);

   return 0; 

}

Output in C:

redeclaration of ‘x’ with no linkage

// Program 2

int x;

int x = 5;

int main()

{

   printf("%d", x);

   return 0; 

}

Output in C:

5

In C, the first program fails in compilation, but second program works fine. In C++, both programs fail in compilation.

C allows a global variable to be declared again when first declaration doesn’t initialize the variable.

The below program fails in both C also as the global variable is initialized in first declaration itself.

int x = 5;

int x = 10;

int main()

{

   printf("%d", x);

   return 0;

}

Output:

error: redefinition of ‘x’