| re: Initialisation
grid wrote:[color=blue]
>
> Hi,
> I have the following code that seems to fail :
>
> #include<stdio.h>
> char c = "hello"[0];
> int main()
> {
> printf("c == [%c]\n",c);
> return 0;
> }
>
> And the below snippet passes :
> #include<stdio.h>
> int main()
> {
> char c = "hello"[0];
> printf("c == [%c]\n",c);
> return 0;
> }
>
> From the standard :
> All objects in static storage shall be initialized
> (set to their initial values)
> before program startup. The manner and timing of such
> initialization are otherwise unspecified.
>
> But I can see in one compiler that it dosent even warn and compiles
> cleanly though gcc cribs about it that "initializer element is not
> constant".
>
> Which behaviour seems to be correct ??[/color]
The externally defined object initialization
requires a constant expression and doesn't have one.
Violation of a "shall" constraint, gives undefined behavior.
N869
6.7.8 Initialization
[#4] All the expressions in an initializer for an object
that has static storage duration shall be constant
expressions or string literals.
6.6 Constant expressions
[#7] More latitude is permitted for constant expressions in
initializers. Such a constant expression shall be, or
evaluate to, one of the following:
-- an arithmetic constant expression,
-- a null pointer constant,
-- an address constant, or
-- an address constant for an object type plus or minus an
integer constant expression.
[#8] An arithmetic constant expression shall have arithmetic
type and shall only have operands that are integer
constants, floating constants, enumeration constants,
character constants, and sizeof expressions.
--
pete
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