Initialization of constants...

[Werner]

Hi all,

The following code snippet does not compile under GCC > 4.6:

namespace { //anonymous
const bool error_notImplemented;
}//end namespace anonymous

Removing the const causes it to compile. I'm surprised by
this behaviour. I would have thought that zero-initialization
would kick in here. I can't make up my mind about what the
standard says about this case. Any hints?

{PS. I realize const bool error_NotImplemented( false ) would be
sufficient and more verbose, but is it required by standard?}

Kind regards,

Werner

 

[Victor Bazarov]

The following code snippet does not compile under GCC > 4.6:

namespace { //anonymous
const bool error_notImplemented;
}//end namespace anonymous

Removing the const causes it to compile. I'm surprised by
this behaviour. I would have thought that zero-initialization
would kick in here. I can't make up my mind about what the
standard says about this case. Any hints?

Since it's a namespace object, it has static storage duration, and it's
supposed to be zero-initialized (i.e. to 'false') before the program
starts. Hence there should be no need to explicitly initialize it (see
[basic.start.init]/2). _HOWEVER_ there is another requirement (see
[dcl.type.cv]/1) which says that "If a cv-qualifier appears in a
decl-specifier-seq, the initdeclarator-list of the declaration shall not
be empty." It means that a declaration of an object with 'const' *must*
have an initializer.

{PS. I realize const bool error_NotImplemented( false ) would be
sufficient and more verbose, but is it required by standard?}

Yes AFAICS.

V