17 Nov
2020
17 Nov
'20
6:51 p.m.
Am 17.11.20 um 10:59 schrieb Fons Adriaensen:
But it doesn't make sense to me.
Yes, we are in the same boat here.
I've always understood 'extern' has
'defined somewhere but not here'. In other words 'extern' must be
part of a declaration, and not of a definition as that would be
a contradiction in terms.
I finally have found something in the C++11 standard. But only in
appendix C that lists the differences to ISO C. There is a rationale,
but I don't get why this is more important than consistency ...
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf
* Change :: A name of file scope that is explicitly declared =const=,
and not explicitly declared =extern=, has internal linkage, while in
C it would have external linkage
* Rationale :: Because =const= objects can be used as compile-time
values in C++, this feature urges programmers to provide explicit
initializer values for each =const=. This feature allows the user to
put =const= objects in header files that are included in many
compilation units.
* Effect on original feature :: Change to semantics of well-defined
feature.
* Difficulty of converting :: Semantic transformation
* How widely used :: Seldom
Uwe