G-Fact 19 (Redeclaration of global variable in C)

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’