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From: pkturner@cup.portal.com (Prescott K Turner)
Newsgroups: comp.lang.c++,gnu.g++.bug
Subject: Re: Linkage & a question on name mangling
Message-ID: <25400@cup.portal.com>
Date: 27 Dec 89 02:27:47 GMT
References: <1545@aber-cs.UUCP> <259312BD.11972@paris.ics.uci.edu>
Distribution: usa
Organization: The Portal System (TM)
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In article <259312BD.11972@paris.ics.uci.edu> rfg@ics.uci.edu (Ron Guilmette) w
rites:
> In article <1545@aber-cs.UUCP> pcg@cs.aber.ac.uk (Piercarlo Grandi) writes:
> > ...
> >Notice that since mangling does not apply to variable names yet...
> 
> Yes.  Can somebody please tell me why that is the case?  It seems to me that
> all of the "type checking" effects that are squeezed out of the linker via
> name mangling function names would be equally applicable to the problem
> of assuring that the types of variables and (extern) const's were consistant
> across object files.  What's the story?

This was a conscious decision documented in Stroustrup's paper on type-safe
linkage at Usenix '88.  The difference between variables and functions is
that in most references to a function name, arguments are present which
neatly determine which overloaded alternative to call.  Consider a header
file which declares
   extern long count;
then in a file which includes this header a user declares
   int count;
   ...  // and refer to count:
   long i = count;
There are two ways to look at this that relate to name mangling:
   1. "count" is an overloaded variable name, and the user is going
      to get the variable declared long.
   2. "count" has inconsistent declarations.
Number 1 is unsatisfactory because this kind of example can surprise the user.
The paper doesn't find it worth discussing.

Number 2 is not supported by name mangling.  Since "long count" and
"int count" would have different mangled names, the linker would not
find the error in the program.
--
Prescott K. Turner, Jr.
Language Processors, Inc.
959 Concord St., Framingham, MA 01701 USA    (508) 626-0006 x232
UUCP: ...sun!cup.portal.com!pkturner    Internet: pkturner@cup.portal.com