Re: C89 "bug"

antispam@fricas.org (Waldek Hebisch) writes:

Thiago Adams <thiago.adams@gmail.com> wrote:

Does anyone knows how can I convert this code (external declaration) to C89?
 
union U {
    int i;
    double d;
};
 
union U  u = {.d=1.2};
 
The problem is that in C89 only the first member of the union is
initialized.

>
The following:
>
union U {
    int i;
    double d;
};
>
union U u = (union U)(1.2);
>
is accepted by 'gcc -S -std=c90'.  I leave to others to check
if this is valid C89.

It's not.  With "-std=c90 -pedantic", gcc (correctly) warns:

    ISO C forbids casts to union type [-Wpedantic]

The specific constraint in the C90 standard is:

    Unless the type name specifies void type, the type name shall
    specify qualified or unqualified scalar type and the operand
    shall have scalar type.

(Later editions have similar wording.)

--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */