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Date: Sat, 24 Nov 2007 11:28:30 -0700
From: Martin Sebor <sebor@roguewave.com>
Organization: Rogue Wave Software, Inc.
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To: stdcxx-dev@incubator.apache.org
Subject: Re: question on the examples for the source/forward/backward
 incompatible
 changes
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Sender: Martin Sebor <msebor@gmail.com>

Mark Brown wrote:
[...]
> Or adding overloads with different behavior to functions that are
> a better match for calls in existing programs. For instance, if we
> added an overload for the ostream inserter for wchar_t* that did
> something different than print the value of the pointer it would
> break programs that insert wchar_t pointers into narrow streams.
> So code like this: std::cout << L"insert a pointer"; inserts the
> address of the wide string today, but if we added the overload it
> would write the string itself.

This is an interesting example because it doesn't actually break
programs at compile time but rather changes their runtime behavior,
something that typically is associated with binary compatibility.
Incidentally, we even have an enhancement request for this new
inserter (maybe you've seen it):
     http://issues.apache.org/jira/browse/STDCXX-296

But there certainly are cases where adding an overload can break
programs by introducing an ambiguity where there previously was
none.

Martin