A question about static.

[User Name:]

From what I understand, in a function, static makes the variable retain it's value between calls to the function. What about initialization, say I have this function:

int functiona(void)
{
    static int number_of_times_called = 0;
    return ++number_of_times_called;
}

Would the variable be initialized to 0 every time I call this, or would it only be initialized to 0 once, retaining it's value from the last call to "functiona"?

[laserlight]

It would be initialised to 0 on the first call to the function.

[User Name:]

What's the difference between const and static?

[laserlight]

const is an abbreviation for constant, and something that is constant should not be changed. static depends on context; you have mentioned one in this thread.

[MK27]

Const is not suppose to change at all.

[quzah]

You can change the value of a static variable, you shouldn't be trying to change the value of a constant variable.


Quzah.

[User Name:]

I think I read somewhere that static used on a global makes it only visible to the source being compiled, is that true, and if so, is that also true for const?

[laserlight]

I think I read somewhere that static used on a global makes it only visible to the source being compiled, is that true

Yes.

is that also true for const?

I do not think so, but I do not have a copy of the C standard at hand to verify, nor do I have a compiler installed. You could check it for yourself, just as you could have checked the answer for your original post in this thread

[MK27]

is that also true for const?

It would be true for a "static const", but for sure not for just const, no.

You could check it for yourself, just as you could have checked the answer for your original post in this thread

Eek! That would require compiling some code!

[User Name:]

just as you could have checked the answer for your original post in this thread

True. I thought of that right after posting, but I couldn't find the delete thread button. But look at the bright side, I'm sure you didn't get to 12104 by only answering good questions, true?

[MK27]

True. I thought of that

As long as everyone is on the same page with this then that's great

[nonoob]

It would be initialised to 0 on the first call to the function.

I would say it's initialized to 0 when the program starts executing. Part of initialization procedure... same as where global variables are initialized. i.e. not part of the execution thread.

[Elysia]

True. I thought of that right after posting, but I couldn't find the delete thread button. But look at the bright side, I'm sure you didn't get to 12104 by only answering good questions, true?

As they say, there are no bad questions, only dumb questions.
Others can learn from your mistakes and curiosity. That is why most boards don't want to delete threads, and this one is no different.

[User Name:]

So basically, it's the abstract form of declaring an integer of the value 0 in the '.data' segment(In other words, it's never initialized, the '.data' segment is initialized at compile time.)? Sometimes the abstraction of HLLs can lead to ambiguity as to what is really being done, especially for someone like me, who sees everything in asm. It's the different structures within the sources that lead to my confusion.

And a const would be in '.rodata', I assume?

[laserlight]

So basically, it's the abstract form of declaring an integer of the value 0 in the '.data' segment(In other words, it's never initialized, the '.data' segment is initialized at compile time.)? Sometimes the abstraction of HLLs can lead to ambiguity as to what is really being done, especially for someone like me, who sees everything in asm.

With respect to the C standard, an object with static storage duration (this include global variables) has a lifetime that is the whole period of execution of the program, and it is initialised before program start-up. The details are implementation defined, so yes, what is really being done is deliberately ambiguous

And a const would be in '.rodata', I assume?

Not really: const may apply to a given context, e.g., you might have a const int* parameter for a function, thus declaring that the int is not to be changed via this pointer parameter. But the int variable in the function that calls this function may well be non-const.