warning about anonymous type

I need to have a single global variable containing some members. I read that using a singleton class is not recommended and really I don't have a need for a class. So I just tested g++ -c on a code fragment:

---------------------------

struct {
	int a, b, c ;
} mystruct ;

class {
	int a, b, c ;
} myclass ;

---------------------------

g++ -c gives me the warnings:

singleton.cpp:7: warning: non-local variable ‘<anonymous struct> mystruct’ uses anonymous type singleton.cpp:13: warning: non-local variable ‘<anonymous class> myclass’ uses anonymous type

However, testing the struct declaration in C does not give any warnings. OK, C++ is pickier than C, so this is fine. But I don't really know what to make of the warnings that g++ gave me. What is the potential problem if a non-local variable has an anonymous type?

Apparently if a **local** variable has an anonymous type it is OK, since I did not get this warning when I put the mystruct and myclass definitions into main(). But I don't get the logic behind:

1) the warning
2) the distinction between local and nonlocal in this case

Please explain.

With thanks as always,

Shriramana Sharma.

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