Date: Tue, 22 May 2001 13:34:58 -0700
To: pgsql-hackers@postgresql.org
Subject: Re: C++ Headers
Message-ID: <20010522133458.H18121@store.zembu.com>
Reply-To: pgsql-hackers@postgresql.org
References: <3B08D94D.AE828050@petig-baender.de>
	<200105220419.f4M4JfQ29720@candle.pha.pa.us>
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	from pgman@candle.pha.pa.us on Tue, May 22, 2001 at 12:19:41AM
	-0400
From: ncm@zembu.com (Nathan Myers)

On Tue, May 22, 2001 at 12:19:41AM -0400, Bruce Momjian wrote:
> > This in fact has happened within ECPG. But since sizeof(bool) is passed to
> > libecpg it was possible to figure out which 'bool' is requested.
> > 
> > Another issue of C++ compatibility would be cleaning up the usage of
> > 'const' declarations. C++ is really strict about 'const'ness. But I don't
> > know whether postgres' internal headers would need such a cleanup. (I
> > suspect that in ecpg there is an oddity left with respect to host variable
> > declaration. I'll check that later)
> 
> We have added more const-ness to libpq++ for 7.2.

Breaking link compatibility without bumping the major version number
on the library seems to me serious no-no.

To const-ify member functions without breaking link compatibility,
you have to add another, overloaded member that is const, and turn
the non-const function into a wrapper.  For example:

  void Foo::bar() { ... }   // existing interface

becomes

  void Foo::bar() { ((const Foo*)this)->bar(); }   
  void Foo::bar() const { ... }   

Nathan Myers
ncm@zembu.com