gnucash master: Add failing unittest for aqbanking lookup of trans_retrieval date.
jralls at ceridwen.us
Mon Sep 8 15:59:45 EDT 2014
On Sep 8, 2014, at 11:16 AM, Christian Stimming <christian at cstimming.de> wrote:
> Am Montag, 8. September 2014, 07:17:47 schrieb John Ralls:
>> On Sep 8, 2014, at 5:31 AM, Christian Stimming <christian at cstimming.de>
>>> Zitat von John Ralls <jralls at ceridwen.us>:
>>>>> recently I noticed the "trans-retrieval" slot in the aqbanking account
>>>>> doesn't remember its value.
>>>> Yeah, fixed and pushed, e210f8c.
>>>> The difference was that your test used the defective accessor function
>>>> and mine used qof_instance_get directly with the right parameter type
>>>> (Timespec ** instead of Timespec *).>
>>> Ah, the wonders of zero compile-time checks of variable argument lists in
>>> Thanks a lot for fixing this!
>> It's not C's fault; C compiler's know the difference between pointers and
>> pointers-to-pointers and how to raise type errors. It's GValue's conversion
>> of everything to void* that defeats the type checking.
> Err... no, it is indeed C's fault: The function in question, qof_instance_get
> and set, uses a variable argument list (variadic arguments), terminated by the
> NULL pointer in the call, and this variable arguments are not at all compile-
> time checked. Using qof_instance_get is what you inserted here in
> 272655b60c0e30726, including the bug you fortunately now fixed. If there is
> another interface that gives us some more compile time checking, feel free to
> propose it here and/or in the docs of qof_instance_get. Or is this just a
> fundamental (bad) property of g_object's property system that we can't avoid?
It’s a fundamental bad property of variadic functions in general, but if the variadic function was calling a strongly-typed function (inside GObject, since qof_instance_get just wraps g_object_get) the compiler would have errored out. Since the GValue functions take void*, the compiler didn’t have a chance.
The interface which gives more compile-time checking uses templates instead of void*, at the expense of some really horrendous compiler error messages. Boosters of the new concepts feature due in C++17 and available in boost claim that it fixes the compiler error problem, but I haven’t tried it yet to see if they’re right.
I think replacing GObject properties and GValues will be part of converting the primary database classes to C++.
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