> Stephan Beal wrote:
>> 2012/2/3 Jorge Eliécer Osorio Caro <jorgeliecer.osorio at gmail.com>
>>
>> > *ppVTab = (sqlite3_vtab*) nr;
>> > ((sqlite3_vtab*) nr)->zErrMsg = NULL;
>> >
>>
>> Please try changing those to the variants from my previous post. i'm not
>> 100% convinced that that cast is strictly legal in C++.
>
> It will work with all the C/C++ implementations I've seen. However, it
> would be better, and more informative, and ultimately more robust, to
> change this code:
> typedef struct NiuRoutingStruct {
> sqlite3_vtab vtab;
> } NiuRouting;
> to this:
> struct NiuRouting : public sqlite3_vtab vtab {
> ... // your implementation, eventually
> };
>
> This way, the casting is unnecessary and any pointer offsetting will be
> done correctly.
Just for my curiosity:
Is the above really equivalent to the C definition like:
typedef struct NiuRoutingStruct {
sqlite3_vtab vtab;
... // your implementation, eventually
} NiuRouting;
?
Reason I'm asking: sqlite uses a pointer to that structure to access
"sqlite3_vtab vtab" member - in machine code that would be
memory offset 0, all other private members start at
+sizeof(sqlite3_vtab)+optional alignment.
Now, I'm wondering if a c++ style of inheritance is defined
in the same way - Note that sqlite relies on that, or better
say "the compiler that produced the sqlite machine code relies
on that".
Just in case the c++ compiler rearrange the byte offset differently
it will crash rights away, I think.
Thanks.
Marcus
>
> The use of C-style casts in C++ is bad practice. Use static_cast where
> you can. The problem with C-style casting is that it can become a
> reinterpret_cast when that is going to produce problems.
>
> --
> Larry Brasfield
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