Is a global or static declaration safer in an embedded environment?

Question

I have a choice to between declaring a variable static or global.

I want to use the variable in one function to maintain counter.

for example

void count()
{
   static int a=0;
   for(i=0;i<7;i++)
   {
      a++;
   }

}

My other choice is to declare the variable a as global. I will only use it in this function count().

Which way is the safest solution?

Answer 1

It matters only at compile and link-time. A static local variable should be stored and initialised in exactly the same way as a global one.

Declaring a local static variable only affects its visibility at the language level, making it visible only in the enclosing function, though with a global lifetime.

A global variable (or any object in general) not marked static has external linkage and the linker will consider the symbol when merging each of the object files.

A global variable marked static only has internal linkage within the current translation unit, and the linker will not see such a symbol when merging the individual translation units.

Answer 2

The internal static is probably better from a code-readability point of view, if you'll only ever use it inside that function.

If it was global, some other function could potentially modify it, which could be dangerous.