Re: GNU Guile 1.9.5 released (alpha)

[Ken Raeburn <raeburn@raeburn.org>]

On Nov 28, 2009, at 20:24, Linas Vepstas wrote:
> googleing the error messages indicates that anonymous structs
> are OK in C, but are somehow bad form in C++, thus gcc
> generates this error. I don't understand why this would matter.

The error message you quoted refers specifically to a function taking  
a SCM argument.  When a C++ function not declared 'extern "C"' takes  
an object or pointer using a struct/class type, the name of the type  
is used in the "name mangling" that encodes the function signature in  
the object-code name for the function; for example, "foo(int)" may  
become "_Z3fooi" (something like: _Z = function encoding prefix, 3 =  
length of function name, i = int), and "foo(struct x)" may become  
"_Z3foo1x" (1 = length of name of user-defined type), but for an  
anonymous type, you can't encode it.

I'm not sure of the rules for anonymous classes in C++; searching the  
1998 standard I see only references to anonymous unions.  My best  
guess is that you're just not allowed to use them for declaring  
objects with linkage, but I can't (so far) quote you chapter and verse  
to support that.

Ken