warning about anonymous type

warning about anonymous type

[Shriramana Sharma]

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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