Name: Ian Cahoon
Member since: 2000-07-19 06:08:18
Last Login: N/A
Homepage: http://ian.cahoon.com
Notes:
I work on vovida.org, providers of open source voice over IP protocol stacks and applications.
http://www.vovida.org/~icahoon
Making a living writing open source software has been a dream of mine since first messing around with Linux back in the 0.92 Slackware days.
I have experience with VoIP, especially h.323, and am currently using the OpenH.323 protocol stack. http://www.openh323.org . It's a nice stack, better in some respects than the some other commercial h.323 stacks, just not as complete.
Had a friend of mine point out the wonderful C++ feature of pure virtual destructors.
I.e.
class X { public: ~X() = 0; }X::~X() {}
This is apparently legal C++ (Sect 10.3 and 10.4). It seems counter intuitive and yet apparently serves a purpose. If no other methods of a class are abstract, a virtual destructor can be used to prevent the instantiation of the class.
As well, it seems it is legal to provide a definition of any pure virtual function. Thus the meaning of a pure virtual method is that it prevents the instantiation of a class and that all pure virtual methods, minus the destructor, can be optionally defined.
This is a slight conceptual difference than what I had thought of pure virtual functions. In practice I have never defined a pure virtual function. And the notion of defining a pure virtual destructor is disturbing. I really believe that explicitly declaring and definition constructors as protected conveys the intent much clearer than a pure virtual destructor ever could.
Sometimes I wonder how stuff like this ever gets into standards.
Just heard about Mozilla's leaky. Wow. I am constantly impressed by the quality (and quantity) of useful things coming out of Mozilla. I really should take a harder look at their code, to see what can be easily reused.
An interesting thing happened using gdb on linux today.
If I try to block on poll() in a multithreaded program,
poll wakes up continuously, thanks to SIG32, aka
SIGRTMIN. Seems pthreads is using this to change thread
contexts, and gdb doesn't seem to get it. However if I
block on pthread_cond_timedwait, this isn't a problem, nor
is it unexpected, since pthread_cond_timedwait can't be
interrupted via a signal. Perhaps there is a gdb
handle command I havent tried yet.
I was thinking about writing a signal handler that caught
SIGSEGV and SIGABRT that basically dumped the stack using
the backtrace call in /usr/include/execinfo.h. Too bad the
linux kernel just won't dump core the right way for
multithreaded programs. Too bad the kernel doesn't know
about pthreads.
I've been thinking about using the sgi's
state threads package. It looks interesting, despite
being NPL.
What I wouldn't do for a g++ that could do precompiled headers.
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