[boost] Re: VC7 and wchar_t in Boost

From: Carl Daniel (cpdaniel_at_[hidden])
Date: 2002-10-20 16:53:17

"Edward Diener" <eddielee_at_[hidden]> wrote in message
news:aov76u$h57$1_at_main.gmane.org...
> The exported function changes mangled signature depending on the type of
> wchar_t chosen by the end user. And of course the different types may be
> different sizes, I'm not sure.

Fortunately, they're the same.  AFIAK, only GCC on Linux defines wchar_t as
other than 16 bits.

>
> Boost has at least one library of which I know there are wchar_t
interfaces,
> regex++, and possibly other implementations where functions and/or member
> functions pass or return wchar_t objects from a DLL rather than through
just
> a header file implementation. If the DLL is created with one type of
wchar_t
> for VC7 and the end user decides to use the other type of wchar_t, program
> havoc and crashes will likely occur. Of course becasue the exported
> interfaces are different, this will be caught at link time before the run
> time problem occurs. The problem no doubt extends to std::wstring which is
a
> sequence of wchar_t characters, but that mismatch will not be caught at
link
> time and only runtime.

Not true.  std::wstring is no different than any other class (after all,
it's written in C++ - all the source code is in the header).  If two modules
that were compiled with different settings for /Zc:wchar_t attempt to
exchange wstrings, there are two possibilities.  !) If std::wstring is
coming from a DLL or static library, then there will likely be errors at
link time.  2) If std::wstring is all inline, everything will "work fine",
since the two types really are identical, even though they have different
names.

It is a mess though...  :|

-cd