donn@utah-cs.UUCP (04/12/87)
The following fragment is accepted by cfront under c++ 1.2 but is
rejected by all of our local C compilers:
------------------------------------------------------------------------
void x() {
struct y {
int a, b, c;
} yy;
yy.a = 1;
}
struct y zz;
------------------------------------------------------------------------
I believe K&R C requires that typedefs obey scoping rules; in PCC
compilers that I'm familiar with, structure tags have the same
constraint. At any rate I tried to compile the example with the
standard C compilers on two System V boxen (an SGI Iris and an HP
Bobcat) and two BSD boxen (a Gould 9080 and a VAX 8600); the VAX
compiler complained about 'undefined structure' and the others
complained about 'unknown size'.
This wouldn't be so bad except that c++ 1.2 cfront passes this syntax to
the C compiler pretty much unchanged. If cfront extracted the struct
definition and generated it into external scope, the C compilers would
have no problem with the translated code; but as things stand, the C
compilers uniformly choke. This little problem may not look very
interesting unless you realize that classes which are declared in local
scope are translated so that members which are not functions end up in
a C struct in local scope. The member functions of such a class are
unable to use other members of the class because member functions are
all generated into external scope to comply with C's rule preventing
nested function definitions...
We've advised our users to avoid declaring structs or classes in local
scope for the time being. Is there a fix for cfront which would help
us out?
Donn Seeley University of Utah CS Dept donn@cs.utah.edu
40 46' 6"N 111 50' 34"W (801) 581-5668 utah-cs!donn