Re: Does the standard specify calling conventions?
On Sep 13, 10:25 am, Stuart Redmann <DerTop...@web.de> wrote:
On 09/13/10 Stuart Redmann wrote:
On 13 Sep., Stuart Redmann wrote:
I stumbled over this when someone in this newsgroup asked about IO
manipulators for his ostream-derived class (see
d1cd356b-9407-481a-8d6c-a5a1151dc...@t11g2000vbc.googlegroups.com). I
posted some code that works under MS Visual C, and would be standard-
conformant WRT calling conventions, but still does work on his
machine:
std::ostream& operator<< (std::ostream& (__cdecl *_F)
(std::ostream&));
cannot be compiled with his version of the STL because it doesn't kno=
w
__cdecl.
Am I getting this 100% right: Above definition of IO
manipulators is standard-conformant? Or are IO
manipulators not part of the standard?
On 13 Sep., Ian Collins wrote:
"__cdecl" is a windows thingy, not used elsewhere.
Right. But is it standard-compliant? According
tohttp://www.cplusplus.com/reference/iostream/ostream/operator<</
I would say no. However, the answers I got this far give me
the impression that the standard does not disallow the usage
of calling convention modifiers. This would mean that above
code would be standard-conformant.
It depends on your point of view. The standard says that
identifiers beginning with __ are "undefined behavior". In
other words, an implementation can do whatever it wants when
a program contains one. In this case, the "undefined behavior"
is there precisely to allow compilers to create extensions
without running the risk of breaking standard conformant
code---both VC++ and g++ make extensive use of this feature.
From a compiler implementor's point of view: adding additional
keywords does not render the compiler non compliant, as long as
the keywords start with __. From a user's point of view: if you
have a symbol in your code which starts with __, that code is
not compliant. It is using an implementation defined extension.
What I actually want is the clarity that the standard
disallows above code (at best with section number and
everything) because else I'll become a LabView programmer
(shudder). Or rather join the forces and become a Ada95
programmer ;-)
=A717.4.3.1.2: "Each name that contains a double underscore (__)
or begins with an underscore followed by an uppercase letter
(2.11) is reserved to the implementation for any use."
--
James Kanze