Hi, >Executing it results in: > >** (process:19834): CRITICAL **: thing_set_property: assertion `self != >NULL' failed > >Apparently the c-version of Thing.set_property makes a call to >g_return_if_fail, which prints the critical message as thing is null. >Shouldn't a programming language, that offers exception handling, throw >some kind of null pointer exception?
Two things:
1) AFAIK checking if self != NULL in the beginning of all member
functions is a common convention in GObject. Vala follows it.
2) There are no null pointer exceptions - checking every object every
time it's used would be too expensive in any sane binary; trapping
SIGSEGV could make more sense, and currently I'm developing a library
that enables possibility to do this. But it's not beyond
proof-of-concept yet, and for some usable shape it needs some time. I'm
lazy.
>Anyway, changing "int property {get;set;}" to "int property;" even
>results in a segmentation fault. It might be discouraged to use a public
>property without getters or setters, but valac should generate something
>saver than :
>
> Thing* thing;
> thing = NULL;
> thing->property = 42;
>
>in this case, shouldn't it? My valac version is 0.11.3.
Well, if you have a _property_, it's a setter & getter functions that
take object instance as a first argument (self). Following GObject
conventions, we just check if self != NULL. But changing it to a
_field_ will make a direct access - so it's perfectly sane to segfault
here, just as in any other C program where you have a structure pointer
== NULL, and try to write to the structure's members.
You may be interested in checking how --enable-experimental-non-null -
Vala will enforce to never assign null or possibly null value to any
reference that's not marked as nullable.
best regards,
>I am sorry, if this is the hundredth time someone mentions this here,
>please point me to the according discussion, if this is the case.
>
>best regards,
>Thomas
>
>
>
>
>
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