Static storage duration question.

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08-10-2010
nimitzhunter

Static storage duration question.

Hi,
I'm reading C Primer Plus by Prata, and he mentioned that if you initilize a variable with static storage duration, then you have to use constant values. I don't understand what he means by 'constant values'. Did he mean that I have to declare my variable with the qualifier "const"?
08-10-2010
Sebastiani

Quote:

Originally Posted by nimitzhunter

Hi,
I'm reading C Primer Plus by Prata, and he mentioned that if you initilize a variable with static storage duration, then you have to use constant values. I don't understand what he means by 'constant values'. Did he mean that I have to declare my variable with the qualifier "const"?

Actually, there is no such requirement.
08-10-2010
laserlight

Quote:

Originally Posted by nimitzhunter

I don't understand what he means by 'constant values'. Did he mean that I have to declare my variable with the qualifier "const"?

No, it means that you should say, use a literal, or an expression that can be resolved as if it were a literal, to initialise an object with static storage duration. It does not mean that all variables with static storage duration must be declared const.

Quote:

Originally Posted by Sebastiani

Actually, there is no such requirement.

Actually, there is:

Quote:

Originally Posted by C99 Section 6.7.8 Paragraph 4

All the expressions in an initializer for an object that has static storage duration shall be constant expressions or string literals.
08-10-2010
Sebastiani

Quote:

Originally Posted by laserlight

Actually, there is:

Heheh. I think this is the second time you've pointed that out to me, too. :D

Why then does GCC not complain with this code?

Code:

int bar( void ) { } int main( void ) { static int foo = bar( ); }
08-10-2010
laserlight

Quote:

Originally Posted by Sebastiani

Why then does GCC not complain with this code?

But it does...

Code:

test.c: In function `main': test.c:6: error: initializer element is not constant

at least for the MinGW port of gcc 3.4.5 with the -pedantic option.
08-10-2010
Sebastiani

Quote:

Originally Posted by laserlight

But it does...

Code:

test.c: In function `main': test.c:6: error: initializer element is not constant

at least for the MinGW port of gcc 3.4.5 with the -pedantic option.

I see. Yeah, I haven't got the "pedantic" switch enabled, apparently (fixed). I wonder why it's required, anyway? Related to initialization order not being guaranteed WRT different translation units or some such?