[Gllug] C/C++ mentor

[Nix]

On 24 Nov 2006, Daniel P. Berrange told this:

> On Thu, Nov 23, 2006 at 11:02:11PM +0000, Nix wrote:
>> So what's your opinion of libdbus-1.0.0+'s charming `check failed? we
>> SIGABRT you' failure mode? If it stays it seems very unlikely that D-Bus
>> will be used by many important services: keeping those services running
>> is often far more important than sending notification messages out.
>
> Well, its a tricky / interesting problem. These assertions are identifying
> real programming flaws, so while I certainly do want key system services
> to run reliably, I equally don't want these flaws being allowed through
> to potentially become security exploits. These checks are usually only
> enabled when dbus is built with assertion checking enabled - in production
> release builds 95% of them disappear to be no-ops.

... except that the docs recommend you *always* build with --enable-checks.
Daniel Stone and others have pointed out that this appears to be honoured
mostly in the breach...

> There was one particularly annoying check though that seems to have
> caused a hell of alot of pain. The API contract of one method was
> changed shortly before the 1.0 release. In doing so an assertion check
> was added to easily detect apps relying on the old semantics. In
> retrospect though, this was probably a mistake because its caused a
> lot of unneccessary & very user visible pain during this transition
> phrase where apps adapt to new API semantics.

Doing it at a point where app developers could reasonably have assumed
that things are stable was not terribly nice either.

> Finally it is worth noting that it really isn't intended for application
> developers to be using the core libdbus.so directly in most cases. It
> was expected that in the general case people would use the higher 
> level language bindings, eg python, glib, qt, perl, java, etc. These
> bindings mask most of the low-level messaging APIs, providing a high
> level API more easily used by app developers. In doing so, these high
> level APIs would protect apps from the possibility of violating any of 
> the assertion checks.

But if by chance your binding is buggy, oops, SIGABRT and you're dead.
A bit tough on the app if sending bus messages isn't its sole reason
for existence.

-- 
`The main high-level difference between Emacs and (say) UNIX, Windows,
 or BeOS... is that Emacs boots quicker.' --- PdS
-------------- next part --------------
-- 
Gllug mailing list  -  Gllug at gllug.org.uk
http://lists.gllug.org.uk/mailman/listinfo/gllug