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<DIV><SPAN class=812595301-19112007><FONT face=Arial
size=2>Robert</FONT></SPAN></DIV>
<DIV><SPAN class=812595301-19112007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=812595301-19112007><FONT face=Arial size=2>Can you explain
exactly in simple english</FONT></SPAN></DIV>
<DIV><SPAN class=812595301-19112007><FONT face=Arial size=2>1. What you have
changed. I assume it's changing every BOOL to PBOOLEAN in
ptlib?</FONT></SPAN></DIV>
<DIV><SPAN class=812595301-19112007><FONT face=Arial size=2>2. So everyone in
every program derived from ptlib/pwlib has to change their program or when they
compile against upcoming releases of ptlib their program will no longer function
properly. Is that correct?</FONT></SPAN></DIV>
<DIV><SPAN class=812595301-19112007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=812595301-19112007><FONT face=Arial size=2>For what
benefit? Compile time checks? moving from BOOL to ANSI bool?
Though I have always wondered why BOOL was used in place of bool and
globally replacing in h323plus is fairly easy however for the
community as a whole who have developed complex applications from these
libraries it's going to be extremely painful as backward compatibility is broken
and worse with C++ virtual they will not even notice it has
even occurred until they run the program. Not a very good situation at
all.</FONT></SPAN></DIV>
<DIV><SPAN class=812595301-19112007><FONT face=Arial size=2></FONT></SPAN><SPAN
class=812595301-19112007><FONT face=Arial size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=812595301-19112007><FONT face=Arial size=2>For this reason
I STRONGLY STRONGLY recommend you don't make this change. IMHO it is
something inherent with pwlib/ptlib and far too painful this late in the game
(after 10+ years?) for minimal benefit for everyone
involved.</FONT></SPAN></DIV>
<DIV><SPAN class=812595301-19112007><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=812595301-19112007><FONT face=Arial size=2>But of course, it
already has been decided and the community have a week to agree
and then it's done. This is what is truely unfortunate.</FONT></SPAN></DIV>
<DIV><SPAN class=812595301-19112007><FONT face=Arial size=2></FONT></SPAN><SPAN
class=812595301-19112007><FONT face=Arial size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=812595301-19112007><FONT face=Arial
size=2>Simon</FONT></SPAN></DIV>
<DIV><SPAN class=812595301-19112007></SPAN><FONT face=Tahoma><FONT size=2><SPAN
class=812595301-19112007><FONT face=Arial
color=#0000ff> </FONT></SPAN></FONT></FONT></DIV>
<DIV><FONT face=Tahoma><FONT size=2><SPAN
class=812595301-19112007></SPAN></FONT></FONT> </DIV>
<DIV><FONT face=Tahoma><FONT size=2><SPAN
class=812595301-19112007> </SPAN>-----Original Message-----<BR><B>From:</B>
h323plus-bounces@lists.packetizer.com
[mailto:h323plus-bounces@lists.packetizer.com]<B>On Behalf Of </B>Robert
Jongbloed<BR><B>Sent:</B> Monday, November 19, 2007 9:31 AM<BR><B>To:</B>
Opalvoip-devel@lists.sourceforge.net;
h323plus@lists.packetizer.com<BR><B>Subject:</B> [h323plus] Introducing PBoolean
- API change alert!!!<BR><BR></DIV></FONT></FONT>
<BLOCKQUOTE dir=ltr
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px solid; MARGIN-RIGHT: 0px">
<DIV class=Section1>
<P class=MsoNormal>If you have written any programs based on
PTLib/OpenH323/H323plus/OPAL, please read this, IT’S
IMPORTANT!!<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>Adam Butcher from Selex Communications submitted patches a
while ago to change BOOL to PBoolean. The reason was so that PBoolean could be
defined as the ANSI standard bool type and we get a whole pile of beneficial
compile time checks. The process found a couple of places where a function had
a BOOL return type but integer (tri-state) values were being
returned!<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>Well, Craig and I had thought of this for a while as being
a “good thing” to do, but lack of time has always been an issue. Now, as we
have been presented with all the hack work, it seems that this is it’s
time.<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>Of course things are NEVER easy. The change has a nasty API
issue that can silently stop user programs from working. It revolves around my
#1 pet hate in C++, if you change the signature of a virtual function,
overrides silently no longer override the virtual. For example:<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoPlainText> //------ in the library<o:p></o:p></P>
<P class=MsoPlainText> class OpalXXX<o:p></o:p></P>
<P class=MsoPlainText> {<o:p></o:p></P>
<P class=MsoPlainText> virtual void
SomeFunction( PBoolean );<o:p></o:p></P>
<P class=MsoPlainText> };<o:p></o:p></P>
<P class=MsoPlainText><o:p> </o:p></P>
<P class=MsoPlainText> //------- in some unchanged dependent code
in another application<o:p></o:p></P>
<P class=MsoPlainText> class MyXXX : public OpalXXX<o:p></o:p></P>
<P class=MsoPlainText> {<o:p></o:p></P>
<P class=MsoPlainText> virtual
void SomeFunction( BOOL );<o:p></o:p></P>
<P class=MsoPlainText> };<o:p></o:p></P>
<P class=MsoPlainText><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>The function MyXXX::SomeFunction() will not be called as it
should be. And the stupid compiler (NONE of the compilers) give any warnings
or indication there is an issue. Way back in the preliminary versions of C++
they did have a keyword “override” which would do exactly what we want, error
if the base class does not have the function being overridden as virtual. The
original designers (Stroustrup et al) took out, for presumably good reasons,
though I cannot for the life of me think what! There is even a number
proposals, e.g. <A
href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2108.html">http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n2108.html</A>,
to put a variants of it back and Microsoft have even done so, <A
href="http://msdn2.microsoft.com/en-us/library/41w3sh1c.aspx">http://msdn2.microsoft.com/en-us/library/41w3sh1c.aspx</A>,
on their latest compiler.<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>Anyway we have to deal with existing compilers and this
problem is really insidious, but we think the gains are worth the pain. And we
have provided a work around for people.<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>So, what we need from you guys is please check out the
PTLib and OPAL in the branches:<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal> <A
href="https://opalvoip.svn.sourceforge.net/svnroot/opalvoip/ptlib/branches/BooleanChange">https://opalvoip.svn.sourceforge.net/svnroot/opalvoip/ptlib/branches/BooleanChange</A><o:p></o:p></P>
<P class=MsoNormal> <A
href="https://opalvoip.svn.sourceforge.net/svnroot/opalvoip/opal/branches/BooleanChange">https://opalvoip.svn.sourceforge.net/svnroot/opalvoip/opal/branches/BooleanChange</A><o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>and compile your programs against it. Now by default it
will use the ANSI bool form of PBoolean, so any overrides of PTLib or OPAL
functions must be changed to use PBoolean instead of BOOL. For those not using
MFC, this is really easy, just do a complete search and replace everywhere of
BOOL to PBoolean (or better yet, just bool) and that should do the job. Oh,
you might like to search and replace TRUE to true and FALSE to false while you
are at it, though you don’t HAVE to do that.<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>Now, for those that simply do not wish to make these
changes, we have a backward compatibility option: use the<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><SPAN
style="FONT-SIZE: 9pt; FONT-FAMILY: 'Lucida Console'">
--disable-ansi-bool</SPAN><o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>option with configure (both Unix and Win32) and PBoolean is
defined as BOOL instead of bool. This should (in theory) be 100% compatible
with the previous signatures. So no changes to applications based on PTLib
need be made.<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>But we need you guys to CHECK THAT THIS IS
OK!<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>We are currently proposing to merge it into the trunk on
Monday 26<SUP>th</SUP> of November, we are happy to extend that if asked, but
will not wait forever, the back merging is really painful!<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>P.S. A random note to developers, the PBoolean is only
there for backward compatibility. It is recommended that any NEW functions all
just use the bool keyword. Use lowercase true and false too.<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>P.P.S. Sorry about all the shouting ... <SPAN
style="FONT-FAMILY: Wingdings">J</SPAN><o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>Robert Jongbloed<o:p></o:p></P>
<P class=MsoNormal>OPAL/OpenH323 Architect and Co-founder.<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P></DIV></BLOCKQUOTE></BODY></HTML>