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Hi,

Can someone explain me why gcc-4.0 gives me the 'Initializer element is
not constant' error with this code ? Everything seems to be constant
here...

#include <stdio.h>
typedef struct { int a; int b;} t;
int main(int argc, char** argv)
{
static t* array[2] = {
(t[1]){ {1, 2} },
(t[2]){ {3, 4}, {5, 6} } };
return 0;
}

Thanks,
Fred

wrote:
> Hi,
>
> Can someone explain me why gcc-4.0 gives me the 'Initializer element is
> not constant' error with this code ? Everything seems to be constant
> here...
>
> #include <stdio.h>
> typedef struct { int a; int b;} t;
> int main(int argc, char** argv)
> {
> static t* array[2] = {
> (t[1]){ {1, 2} },
> (t[2]){ {3, 4}, {5, 6} } };
> return 0;
> }

A compound literal is not a constant.

Robert Gamble

wrote:

> Hi,
>
> Can someone explain me why gcc-4.0 gives me the 'Initializer element is
> not constant' error with this code ? Everything seems to be constant
> here...
>
> #include <stdio.h>
> typedef struct { int a; int b;} t;
> int main(int argc, char** argv)
> {
> static t* array[2] = {
> (t[1]){ {1, 2} },
> (t[2]){ {3, 4}, {5, 6} } };
> return 0;
> }

Static objects (such as `array` in the program), when initialized,
require their initializers to be constant expressions. The elements of
`array` array are of type t*, a pointer, so their initializers should
be address constants. However, compound literals in a function are not
static objects, and thus the addresses are not constants and can not be
taken as the initializers.

Robert Gamble a écrit :

> wrote:
> > Hi,
> >
> > Can someone explain me why gcc-4.0 gives me the 'Initializer element is
> > not constant' error with this code ? Everything seems to be constant
> > here...
> >
> > #include <stdio.h>
> > typedef struct { int a; int b;} t;
> > int main(int argc, char** argv)
> > {
> > static t* array[2] = {
> > (t[1]){ {1, 2} },
> > (t[2]){ {3, 4}, {5, 6} } };
> > return 0;
> > }
>
> A compound literal is not a constant.
>
> Robert Gamble

OK, I see, but is it only a C restriction ? Because it seems that
everything can be known at compile time in this code so that the
compiler should be able to do something in this case.

whyglinux a écrit :

> wrote:
>
> > Hi,
> >
> > Can someone explain me why gcc-4.0 gives me the 'Initializer element is
> > not constant' error with this code ? Everything seems to be constant
> > here...
> >
> > #include <stdio.h>
> > typedef struct { int a; int b;} t;
> > int main(int argc, char** argv)
> > {
> > static t* array[2] = {
> > (t[1]){ {1, 2} },
> > (t[2]){ {3, 4}, {5, 6} } };
> > return 0;
> > }
>
> Static objects (such as `array` in the program), when initialized,
> require their initializers to be constant expressions. The elements of
> `array` array are of type t*, a pointer, so their initializers should
> be address constants. However, compound literals in a function are not
> static objects, and thus the addresses are not constants and can not be
> taken as the initializers.

OK, I tried to initialize/declare 'array' in the global context, and it
compiles. I can't understand why those compound literals are not static
in a function. Can anyone tell me ?

f...@mayot.net wrote:

> OK, I tried to initialize/declare 'array' in the global context, and it
> compiles. I can't understand why those compound literals are not static
> in a function. Can anyone tell me ?

6.5.2.5 Compound literals, paragraph 6:

.... If the compound literal occurs outside the body of a function, the
object has static storage duration; otherwise, it has automatic storage
duration associated with the enclosing block.