I have declared two global variables of same name in C. It should give error as we cannot declare same name variables in same storage class.
I have checked it in C++ — it gives a compile time error, but not in C. Why?
Following is the code:
int a;
int a = 25;
int main()
{
return 0;
}
Check it out at : Code Written at Ideone
I think this probably is the reason
Declaration and Definition in C
But this is not the case in C++. I think in C++, whether the variable is declared at global scope or auto scope the declaration and definition is happening at the same time.
Could anyone throw some more light on it.
Now when I define the variable two times giving it value two times it gives me error (instead of one declaration and one definition).
Code at : Two definitions now
int a;
int a;
int a;
int a = 25;
int main()
{
return 0;
}
2 Answers. Show activity on this post. In C, multiple global variables are "merged" into one. So you have indeed just one global variable, declared multiple times.
Said in simple terms, if multiple variables in a program have the same name, then there are fixed guidelines that the compiler follows as to which variable to pick for the execution.
C allows a global variable to be declared again when first declaration doesn't initialize the variable.
It's not possible, an if statement has no special scope, so you can't have two variables with the same name within the same scope and access both, the latter will overwrite the former, so they should have different names.
In C, multiple global variables are "merged" into one. So you have indeed just one global variable, declared multiple times. This goes back to a time when extern
wasn't needed (or possibly didn't exist - not quite sure) in C.
In other words, this is valid in C for historical reasons so that we can still compile code written before there was a ANSI standard for C.
Although, to allow the code to be used in C++, I would suggest avoiding it.
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