[PATCH] do not call _dbus_warn_check_failed on checks

uwesmail2005-lkml at yahoo.de uwesmail2005-lkml at yahoo.de
Wed Nov 15 12:18:55 PST 2006

--- Daniel Stone <daniel at fooishbar.org> schrieb:

> On Mon, Nov 13, 2006 at 07:52:03PM -0500, Havoc Pennington wrote:
> > OK, I'll write the treatise on this and hopefully put it to bed.
> If only. :)
> > 1. The checks are only a helpful debugging feature, and feel free
> to
> >    turn them off
> > ===
> > 
> > If you just want to experience what libdbus would be like without
> these 
> > pesky checks for your bugs, build with --disable-checks. Now your
> bugs 
> > will be "ignored" - most libraries work like this.
> Yes, except the distributions all build
> And my bugs won't be 'ignored'.  You're missing the point entirely; I
> don't want libdbus to continue if it knows it's in an impossible
> situation.  I don't want you to remove all the check lines.  I want
> you
> to change them to return NULL, return -1, *errval = YOU_HAVE_FAILED
> &&
> return, or whatever helps you sleep best.
So what should it do when you call a(ny!) libdbus function after you
that error. I think that means "continue" (using libdbus), when libdbus
knows it's not safe. Error again or may it exit() please?
> libdbus is not, it must be said, a simple library.  What you're
> talking
> about is not even checking against NULL pointers being passed in
> (which
> I'm careful to guard against), but what if I pass in a slightly
> invalid
"slightly invalid" such fine words for abusing other programs.
Invalid is NOT valid. Trying to handle "Slightly invalid" is where
security faults come from.
> message due to a bug on my side?  What if I'm dealing with an
> incoming
> message and only read half the args before I decide I don't want to
> know
> any more about it -- because it's a treacherous message trying to
> poison
> the server -- and throw it away?  It's entirely conceivable that
> someone
> could assert() on unref because all the args weren't inspected.
Read the doc. As long as there is no requirement to inspect all args
that assert() (and all other things, even reporting a DBusError) would
be the bug.
> Note the 'critical paths' thing here: if I fail to deal with input
> hotplug properly, I take all the reasonable precautions to ensure I
> don't segfault in my _own_ code.  If libdbus takes precautions to
> ensure
> it doesn't segfault in _its_ code, then that's fantastic.  I know it
> can't extend to all situations, such as an invalid pointer.  But I
What you say here is "I want no SEGV in *my* code! I know a mere
library can't detect all that situations, so I will try to foist off
that situations onto the lib (and the libs errors in turn) until the
lib breaks. So *my* code will be blameless!"? Did I understand;-)?
> still
> want it to have a defined 'you screwed up' return value, for
> non-obvious
> situations like 'the message is invalid for this bus', 'one of your
> arguments is NULL, and this was fine in previous versions but not
> anymore', etc.
> So, say I somehow fail at adding an input device.  Why should that
> bring
> down my server in such an unclean way that the next attempt to switch
> VTs or start X again, will result in a completely wedged system (no
> SysRq for you, hope everything was saved and your disk synced)?  Why
> should it bring down a word processor so hard it doesn't have a
> chance
> to save?
> You're optimising for shit coders.  And that's great, if you want to
> do
> that, then you can, but I like to think that X and most open-source
> projects can do better than that, and will.
Because you seem to be such a shit coder, I wonder why you sound so
indignant. A real programmer knows that SIGABRT core dumps, and when
the core limit isn't 0 (which it shouldn't be for daemons in my
such a core can be loaded into gdb and even tried to continue and the
programmer can see all the mess that would result from such an attempt.
> > 2. The warnings are not "harmless" if you are in nonfatal warnings
> mode
> > ===
> > 
> > Let's consider the libdbus-never-aborts case. Your best case is one
> > warning to the console. Another likely case is tons and tons of
> warning 
> > spam in .xsession-errors or syslog since something that happens a
> lot is 
> > buggy. Another likely case is that libdbus returns NULL you weren't
> > expecting, and your app crashes. Another likely case is that
> libdbus 
> > itself gets confused somehow - maybe down the line, since e.g. a
> header 
> > field that should have been set wasn't, etc. The backtrace from the
> > later confusion will not reflect the root cause. And then a worst
> case, 
> > short of crashing right away, is that you were e.g. relying on
> having 
> > sent a message, and now you haven't; and either you send another
> message 
> > that semantically relied on the first, or you block waiting for the
> > first message, or whatever, and your app hangs or grows more and
> more 
> > confused.
> Logs filling up happens, people deal.  If libdbus returns NULL you
> weren't expecting, and you crash, then it's provably your bug.  If
> libdbus returns NULL and you catch it, then you can decide exactly
> what
> to do with this error.  Kind of like open returning a negative value,
> rather than assert()ing because the programmer was too stupid to call
> access().
> I'm not arguing for these checks to be removed entirely -- not even
> remotely.  What I'm suggesting, is that the checks turn from 'your
> entire machine suffers a fiery assert() death', to 'define an error
> return value in the API, use it'.
> Bad coders here will still get punished.  Generally rigid coders who
No they won't check that error and what should libdbus do then?
> happen to slip up somewhere will get the opportunity to do the right
Slip up is the same as a bug. A bug is a bug. Leavig the bug in and
paper over is bad coding. The right thing would be to fix the bug. No
check could avoid this task.
> thing, instead of forcing the vision of purity on all the world and
> removing all bugs ever, or something.
> (Think of corner cases where you can't reproduce it normally.  If you
>  can log something useful, maybe even throw an exception and get a
>  backtrace, then the good coder will be able to find out what's wrong
>  despite having no way to reproduce it, and maybe fix it.  assert()
>  gives you no useful information at all, ever, and enforces its own
>  worldview on the app.)
assert() gives you a complete memory dump! Where do you get more info?
> > These cases assume libdbus even *has* a check for your bug. If you
> pass 
> > an invalid pointer instead of NULL, or just do something that's 
> > expensive to check for, then libdbus won't have a check and you'll 
> > probably get an immediate crash.
> If libdbus does not have a check for your bug, then assert() does not
> help, so this is irrelevant.
No it is not. If it crashes due to one bug, but not because of the
other, you would have paid the price (heavy bug checking code in
the program) and got not even a crash proof program in return.
> > Anyway, if you use the API in an undocumented and undefined way,
> whether 
> > the checks are fatal or just warn, or even exist, the results are
> *in 
> > practice* *not* *in theory* often catastrophic and quite bad. And
> often 
> > include crashing or hanging sooner or later.
> Sure.  If I pass in message=0xfffffffffffffffe, then I would expect
> bad
> things to be happening.  Nothing can prevent that.  But you're going
> off
> on an irrelevant tangent again: when libdbus _detects_ an error it
> _knows_ about, it should tell you, rather than blowing up your house,
> and shooting your dog.
And how should it tell you buried three levels deep in other libs?
Which would be the common case BTW. Remember: No program should
use libdbus directly. So you have at least the binding, then possibly
some object proxy layer and possibly a library that uses remote
objects and doesn't want to be bothered with returns from the
(proxied) object method that are due to a failed connection and have
nothing to do with what is documented about that method in the original
object. How that library will handle these (perfectly recoverable)
errors? Guess what: abort() when it's friendly exit() when not.
> I can guarantee you that this will lead to _loss_ of information. 
> When
> the X server goes down that hard, nothing will be usefully logged,
> you
> will just end up losing very badly.  So all people know is that the X
> server came down hard, gdm restarted and then hey, IERR.  As opposed
> to
> useful logged information about what happened and possibly why. 
> Again,
> this penalises good coders, by optimising for rent-a-coders.  If
> that's
> the direction you want to take, then I'm glad for you, but not
> personally interested.
> > This seems to confuse people though; they think they can "recover"
> from 
> > these undocumented, undefined situations. Those people probably
> also 
> > catch SEGV and try to continue.
> Awesome, a strawman.  You can check Xorg and KDrive's segfault
> handlers
> if you like, and note that this is provably untrue.
> > 3. Whether the behavior of passing NULL should be
> documented/defined
> >    is an independent issue
> > ===
> > 
> > If the docs say "passing in NULL results in XYZ" then we *never*
> use 
> > _dbus_return_if_fail; there will be unconditional,
> always-compiled-in 
> > code to handle that NULL which will neither abort nor warn. (Unless
> the 
> > docs are "defined to abort" or "defined to warn")
> > 
> > Feel free to argue that specific API dbus_blahblah should accept
> > for a particular argument. If we document that, then the results
> will no 
> > longer be undefined (and this discussion is not relevant).
> Make your undefined behaviour less obnoxious.  At every single point
> where you have an assert(), wonder what a useful way to signal an
> error
> back to the _application_ consumer of your _library_ is, such that
No _application_ consumer there. The consumer is another library.
Of course it would be interesting if (e.g.)libcups functions show
some DBusError* params, so that the application can log that errors
to catch some bugs in libhal. I think signal(SIGABRT,...) in the
main() function is easier.
> they
> can signal the user, who should obviously be forced to care about
> D-Bus
> errors.  Then change your asserts, to returning errors.
Huh? The USER should care about programming(!) errors? Could you choose
something less obnoxious? Please?
> If the app is buggy, then the app is buggy, and it'll crash.  If the
> app
> is careful, with a subtle typo or race somewhere, but the people who
> wrote it were careful enough to check for errors, then they'll decide
> what's appropriate.
Appropriate is fixing the typo;-) No decision needed.
> > 4. Defining NULL-passed-in for every function in the API would
> >    significantly suck up the API
> > ===
> > 
> > The real issue is that a bunch of people want passing NULL pointers
> to 
> > have defined and documented results. I'm sorry, but I think this is
> > silly. We'd be adding DBusError* returns to any function that took
> a 
> > pointer arg, just so it could return a "you passed in NULL" error.
> If 
> > you want to know if you're passing in NULL, then look at the
> pointer 
> > before you pass it in and see if it's NULL.
> > 
> > IOW the code if we allow NULL is something like:
> > 
> > init_error(&error);
> > dbus_frobate(myptr, &error);
> > if (null_arg_error_set(&error)) {
> >    // well, what are you going to put in here? I sure don't know
> >    // and that's why the error isn't returned
> > }
> No, you write this:
> if (!myptr)
>     return;
> dbus_frobate(myptr, &error);
> if (dbus_error_is_set(&error)) {
>     /* some incredibly obscure check triggered, no-one cares */
>     g_error("loss");
> }
A check is usually triggered when either the internal data are hosed
because of earlier more obscure (latin for hidden) bugs or the params
indicate that probably your data structs are hosed. If you want to
diagnose that (tracing your data from some known references) you need
the full call stack. In such a situation libdbus should not return to
preserve the call stack. If you don't want to diagnose that situation
the program should not continue, because of possible further data loss.
abort() lets you do both: If you do nothing, it stops the program and
dumps memory, if you catch SIGABRT it calls down into a handler and
even if you want to go to a  defined state, there is longjmp() which is
guaranteed to work in signal handlers.
> > If you are masochistic enough to want to write that, you are
> welcome to 
> > write this instead:
> > 
> > if (!myptr)
> >   // whatever
> > else
> >   dbus_frobate(myptr);
> Yes, and people do.

> > 5. Comparison to "wrapper libraries" like Xlib, GNU libc
> > ===
> Before we start here, let me say that Xlib is a) provably not even
> close
> to the API you want, b) provably close to the API you have.
> If you don't believe me, look at X's error handling, and the I/O
> error
> handling (a grossly overloaded term) in particular.
> > These "wrapper libraries" take some args in the process space of
> your 
> > app, and pass them to another process or the kernel, and may return
> a 
> > runtime error either generated in-process or as returned from the
> other 
> > process/kernel.
> Yes.
> > The wrappers generally do one of three things with NULL or
> otherwise 
> > invalid arguments:
> >  a) crash (or behave in other undefined way)
> >  b) pass the invalid arg to X or the kernel and let an error be set
> >  c) set an "invalid arg" error themselves in-process
> Yes.
> > dbus will also do one of these three, as appropriate to the API at
> hand.
> assert() is never, ever, appropriate.  There's no excuse.  This to
> me,
> is axiomatic, coming from my attempted (foolish) use of D-Bus
> somewhere
> where assert() leads to IERR.
Ok alternative to assert(): call a function pointer. Leave as NULL 
SEGV results, or set to a recovery function, that is called instead.
Oh wait! Why don't we call that function pointer assert and the
function to set it signal()?;-)
> > However, for most NULL pointers dbus will do a) because of points
> 3) and 
> > 4) I've already covered. Also, there's no way to pass NULL over the
> bus, 
> > and many of the pointers you're passing in have no protocol
> equivalent, 
> > so b) doesn't even make sense.
> Right, so we're down to 'crash', or 'gracefully return an error to
> the
> callee'.  Honestly, I know which one I'd pick (D-Bus is not code that
> desperately needs to be performant as it's on the critical path, so
> you
> can't use glibc as a parallel).
> > glibc and Xlib I'm pretty sure have a number of examples of a),
> also.
> > I always program as if they do; what happens if you pass NULL to 
> > XDisplayName() or fread()? I don't know, but I doubt it means my
> program 
> > will work as intended.
> Yes, glibc has a number of examples of a) on performance-critical
> paths,
> but, shockingly, lots more of c).  Xlib has a lot of b), and still
> quite
> a bit of c).
> > Remember that return_if_fail() is a subset of a). When libdbus
> would 
> > have done return_if_fail with a handy warning, glibc and Xlib would
> > typically just crash or something else bad (like --disable-checks).
> Um, this is not actually the case.  But maybe I just have strange
> ideas
> about what APIs I use should do.
You don't know what they really do. So you insist on changig them only
because the function you really search is there but not found by you.
And of course you go to all length to not really saying what you want
because it's silly even by your own diminished standards and badmouth
the whole API instead. I'm imagining what you would have said if
the API would me more windows-like:"Most errors are undocumented. How
should I find the really important errors? Couldn't there be a list
of functions where the error is never set. I feel silly writing
that huge switch statement where I discovered later that function
ignores the error* completely. So many time invested for nothing!"
> > 6. Comparison to Windows API
> > ===
> > 
> > Some people are used to the Windows API, which *does* return an
> > from every single call, and at the start of every single call
> checks for 
> > NULL pointers and returns a failed HRESULT if they exist.
> I haven't used the Windows API since I was tooling around with ISAPI
> filters when I was 10.  But this seems like a decent idea to me.  If
> you
> can check, and it won't provably cost the application in terms of
> performance for you to do so, why not?
Because to make it really consistent, you would have to have an
error check on the error checking function. How would you check
for an error in dbus_error_init()?;-)
> > Also, it's completely unhelpful for debugging, because often you
> pass in 
> > a big struct full of info, and you get an error like "there was 
> > something invalid in that struct somwhere" - thanks for the help,
> guys...
> Um.  assert() brings your entire program down roughly because you had
> something invalid in that struct somewhere.  return NULL brings your
> entire program down gracefully (or allows you to continue, at the
> app's
> discretion: again, poor apps will be poor apps regardless, whereas
> good
> apps can work out the criticality and isolation, and continue on if
> they
> feel it's safe) because you had something invalid in that struct
But that's the relevant part: The APP feels safe. It won't and can't
consider the safety of the libs it uses. Some of them might be affected
by some really nasty bugs in a data struct. There was the case of a
lib turning some blank *temporarily* into a '\0' for parsing a string.
By really clever malloc()ing that app could be brought to exec a shell.
The data struct was only *temporarily* buggy. But that sufficed.
> somewhere.
> If you're arguing for fine-grained errors to be returned to the app,
> then sure, go ahead.  But assert() ain't it.
More finegrained than assert() is probably impossible. The whole
application state will be frozen. Even the stack is changed. But only
a good programmer can work with it. For the others there is gdb.
> > And of course if you pass in an *invalid* non-NULL pointer Windows
> can't 
> > do anything, it will often crash.
> Of course it can't.  But that's no excuse to assert() on a NULL
> pointer.
The assert is only printing the reason before crash. So if you
crash anyway, whats wrong with printing the reason if you know it.
> > I'd rather have a nice warning and orderly exit, than an unhelpful
> error 
> > code or silently trying to continue or crashing.
> You aren't even making any sense.  First, you're arguing for
> libraries
> to randomly assert(), bringing down whatever was foolish enough to
> link
> them in.  Now you're arguing for nice warnings and orderly exits,
> rather
> than either unhelpful error codes ('_dst == NULL in
> dbus-message.c:97 oh my god the sky is falling') that mean nothing to
> the user and are thoroughly useless to the developer, or continuing
> and
> crashing?
exit() doesn't preserve state that abort() does. Very helpful. The
core file is very useful for the developer and the error code is
only an indication which developer should get the core file.
(The one that greps for it). To be recognized by grep the error code
has to be as constant as possible. So that would mean in can't contain
many information. Which makes it unhelpful treated by itself. But as
routing for a core file? Very valuable. That could even be automated
cvs annotate|grep assert|sed 's/.../.../' >dat
mail `fgrep -f dat <mail|sed ...`
> If your mail consisted solely of this paragraph, I'd construe it as
> violent agreement.
> > Now point-by-point on Daniel's mail:
> > 
> > Daniel Stone wrote:
> > >I was discussing this over dinner tonight, and someone asked me
> why I
> > >was mixing up the critical (X server) and non-critical (D-Bus)
> paths.
> > >My reply was that I decide what's critical and non-critical.  If
> it's
> > >truly broken, then I'll call FatalError().  If not, I'll just log
> a
> > >message about it.
> > 
> > What we're talking about here is what happens if you use libdbus in
> an 
> > undefined, undocumented, and therefore *unintentional* way.
> > 
> > You won't decide whether to call FatalError() because you aren't
> going 
> > to call dbus this way on purpose. You will only call it this way if
> your 
> > program has a bug. There is no way to write:
> > 
> >  message = dbus_message_new(...);
> >  if (check failed)
> >    FatalError()
> Your assertion here is not even vaguely correct, because you seem to
> miss the point of APIs that have defined error returns.
>         if (!dbus_message_iter_init(message, &iter)) {
>             ErrorF("[config] failed to init iterator\n");
>             dbus_error_free(&error);
>             return DBUS_HANDLER_RESULT_NEED_MEMORY; /* ?? */
>         }
> I find it odd that all the functions you're claiming have no way to
> ever
> possibly return an error under any circumstances known to mankind,
> already have defined returns for having run out of memory.  Instead
> of,
> y'know, assert(foo = malloc(...));
No, he claims that these functions never return an error that is NOT
"out of mem".
> Since you're pretty screwed if malloc() is returning NULL, surely. 
> (I
> think even the X server, which is pretty careful about these sorts of
> things, inadvertently does five or ten malloc()s in its fatal error
> path.)
> > Because there is no way to know that a check failed. DBus does not 
> > return an error code from *every function that takes a pointer that
> > could be NULL*, thankfully.
> You say thankful, I say flawed, shortsighted, and irritatingly lazy
> design.
In C++ you would write a reference there. If you don't give a reference
you get a type error from the compiler. A reference is never NULL.
These assert()s are something like that type error from the compiler.
In C you can use one variable to store some types in some situations
and other types in others, because the compiler can't detect this, but
that doesn't mean it's a good idea. So the assert()s are there to not
let you get away with this. I think it would be better, to use some
typdefs (typedef void* voidref;) to document this intent clearly.
> > >I'm somewhat bemused (and rather depressed) that the upstream
> attitude
> > >is that D-Bus is a core component on exactly the same level as the
> > >kernel (this was one of the justifications for never being able to
> > >restart D-Bus), yet it does things like throw assert()s.
> > 
> > You're confusing three cases.
> > 
> >  - internal bugs in the module (dbus or kernel). _dbus_assert() in
> dbus,
> >    and an Oops for the kernel.
> No.  Internal bugs in the kernel are generally BUG_ON(), not OOPS(). 
> An
> oops is 'if I allow you to continue, then data loss will occur'.  A
> bug
> is just that, a bug.
> D-Bus conflates the two cases here into assert().
Because D-Bus has only data loss when bugs are there.
> Go read kernel code some day, and then come back and tell me that
> no-one
> bothers performing error checking, and that every single error ever
> produced by the kernel results in an oops.
> >  - another process sends junk to the module. This means libdbus
> received
> >    bad data/args from another app, or the kernel gets bad system
> call
> >    args. This leads to dbus returning a message of type ERROR or
> >    disconnecting the remote app, but libdbus will not abort the
> current
> >    app. The kernel in these cases returns a syscall error.
> > 
> >  - the same process uses the module in an undocumented/undefined
> way.
> >    The kernel analogy might be a device driver misusing core kernel
> >    APIs, or something like that.
> >    In dbus, *often* but by no means guaranteed there is a "check"
> >    (dbus_return_if_fail) to help you debug this. In the kernel, you
> >    are likely to get crashes, deadlocks, or even data loss.
> You're engaging in excess semantics here, by using the value of the
> context to differentiate.  That gettimeofday() or open() makes a
> syscall
> is basically irrelevant to me.  Point is, my app makes a function
> call,
> and I'm going to be pretty annoyed if it results in an assert().
> Context is irrelevant, the usage is the same.
> If I call dbus_message_init() or something, and it asserts on errors,
> rather than returning NULL using the already-defined API to signal an
> error to the calling application, I will be incredibly irritated.
Now think like a C++ programmer that calls a function with another
type than expected. Will he be incredibly irritated because the
compiler does not compile the program? But as a C programmer you
expect 1+"2" to compile (which it does, btw). But to expect 3 as
answer is too much. Neither is it "12".
> > > Given the
> > >situation today, your app doesn't even have to link to D-Bus for
> libdbus
> > >to be killing your app hard with asserts.
> > 
> > This is flat out wrong. If libdbus crashes due to the actions of 
> > *another process* than the one libdbus is inside, then it's a bug
> in 
> > libdbus. (OK, unless the other process is root running "kill" etc.)
> > 
> > The other process is untrusted and all data from it gets validated,
> and 
> > if there's bad data then libdbus will send an error or disconnect
> from 
> > the bad process.
> > 
> > If *you* in your app *trust* another app not to crash and it's
> buggy and 
> > crashes, then yes you are hosed. But that is your own fault and
> libdbus 
> > gives you the tools to recover gracefully. No return_if_fail checks
> will 
> > be involved.
> That is all true, but it does not change my statement.  But, 
> s/link/directly &/ for clarity, and maybe now you see what I'm
> getting
> at.
> > >Seriously, the behaviour doesn't even vaguely make sense at all. 
> For
> > >development, sure.  But there's a reason why the kernel, all POSIX
> APIs,
> > >in fact every API ever, X, HTTP, etc, return you errors when you
> ask for
> > >something invalid (a file that doesn't exist, an invalid URL, a
> > >malformed message), rather than ungracefully slaughter you.
> > 
> > The dbus *protocol* behaves just like the syscall interface or X 
> > protocol or HTTP; it doesn't trust the other side. What we're
> talking 
> > about here is the libdbus *library* which is in your address space
> and 
> > all your usage of it is trusted and known to you.
> Right, so we just need someone now to rewrite libdbus, with more
> sound
> design principles.
The design principle is sound: g_return_if_fail is a deferred type
error, that wasn't detected until runtime. Blame the compiler. Or
better the language definition of C.
The program shouldn't have existed at all in the first place.
> > The GLib and GTK+ policies are exactly the same as libdbus, except
> they 
> > only warn by default. Recent devel releases of GNOME have gone to
> fatal 
> > by default, however.
> > 
> > I prefer fatal by default because it keeps people from being
> confused 
> > about what "undefined" means. i.e. they seem to think it means 
> > "magically read my mind and figure out how to work around the bugs
> in my 
> > app" instead of "what you requested makes no sense, so nothing
> sensible 
> > has occurred, and your program still thinks whatever you intended
> *did* 
> > occur, so will continue on doing more things that make no sense,
> and 
> > it's impossible for either the library or your app to know what the
> > results will be"
> Again, I don't want libdbus to continue.  Continuing with
> dbus_message_send on a NULL message obviously makes no sense.  Or
> whatever convoluted checks libdbus has.  But the way to deal with
> this,
> if you're allegedly a low-level library, is to tell the app what it's
> doing makes no sense.
No it doesn't make sense to continue an app that shouldn't even have
been compiled.
> strcpy() gets away with this because it's a brutally simple API, and
> nothing could possibly go wrong.  It's also generally implemented in
> asm, which should also tell you something.
> libdbus is many things, but 'brutally simple' is not among them.
> > If you still don't want to treat these check failures as serious
> bugs 
> > and possible crashes, you are welcome to
> putenv("DBUS_FATAL_WARNINGS=0") 
> > at the start of main(), and take your chances.
> That is not what I want at all.  I want to know about any errors.
> D_F_W=0 hides all the errors from me (the fact you use 'warnings' and
No it logs them to stderr. That you won't see stderr from a daemon make
no difference.
> 'fatal' in the same sentence should set off alarm bells, btw), and so
> does assert(), but with the added bonus of an IERR later down the
> track.
> I honestly don't understand your aversion to signalling errors to the
> app.  You're labouring under some bizzare, misguided, notion that
No, he signals the error to the app. But directly to the app.
No intervening librarys are involved. You want to signal to the
caller. That is almost never (when libdbus is used like it should) the
> this
> will fix all the app bugs in the world.  People who want to write
> crap
> apps will write them, full stop.  They'll do them despite your best
And that seems to include you. What you lobby for is making an API
that makes it easier to write crap, but harder to write correct code.
A general DBusError return for instance makes the handling of
OOM more complicated because that DBusErrror must be checked for
type error or OOM. And in the production code that check isn't
even needed, because type errors should not have gone there.
That code must be written when now a simple if(func()) suffices.
> efforts, and there's nothing you can do to stop them, except warn
> people
> against using these horrible apps that cause data loss.
> By optimising for this situation, you're penalising otherwise honest
> developers who are capable of writing good apps, but make typos every
> now and then, or manage to get caught in horrible race conditions. 
The core dump of abort() would give the developer the exact state of
the race condition, whereas he would have to try thousands of times
to reproduce the exact conditions that let there.
> I'd
> rather my APIs were optimised for people who can get out of bed
> without
> injuring themselves, and people who have no idea about development
Development is not hacking source code, it's planning what to do, what
interfaces are needed between parts of an app and some others. But all
of them profit from type safety. That's why C++ was invented.
libdbus is written in C (I want to reimplement in C++ someday). So
some type safety has to be introduced via the backyard. And you want
that type safety removed, because you can't develop in a type safe(r)
language? What do you call Development?
> can
> just suffer anyway, because either they'll avoid D-Bus, or find new
> and
> creative ways to make mistakes.
> Cheers,
> Daniel
> > _______________________________________________
> dbus mailing list
> dbus at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dbus

Telefonate ohne weitere Kosten vom PC zum PC: http://messenger.yahoo.de

More information about the dbus mailing list