Re: [Vala] conversion segfault

[Andre Masella <andre masella name>]

If you look at the generated code, you will see:

_tmp1_ = g_strconcat ("foobar", (const gchar*) test, NULL);

for line 4, which is not what you want. When you use an explicit cast on
any type other than a GObject, Vala doesn't know how to do a conversion, so
it does whatever conversion C would do. That usually means converting
integers from one type to another, but it can also mean converting an
integer to a pointer, as in this case.

If you do:
    string x = "foobar" + x.to_string();

it will compile to:

test = (guint64) 1;
_tmp1_ = g_strdup_printf ("%" G_GUINT64_FORMAT, test);
_tmp2_ = _tmp1_;
_tmp3_ = g_strconcat ("foobar", _tmp2_, NULL);

Which is probably what you want when using the + operator.

If you use an interpolated string:

     string x = @"foobar$(test)";

You will get the same code as Vala will automatically call `to_string` on
any non-strings that are embedded.

The reason the direct cast behaviour is needed is there are legitimately
non-string things that are strings. For instance, if you have an array of
uint8[], a direct cast is desirable.

    uint8 data[12];
    data[0] = 'a';
    data[1] = '\0';
    string x = "foobar" + (string) data; // Just fine and exactly what I
intended.

I agree it's not what a typical VM language would do, but Vala is trying to
have C compatibility.

On 6 February 2015 at 06:01, Daniel Brendle <grindhold skarphed org> wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Hello, fellow Valaists
>
> I have the following example code which segfaults:
>
> public int main(string[] argv){
>     stdout.printf("hello world\n");
>     uint64 test = 1;
>     string x = "foobar"+(string)test;
>     stdout.printf(x+"\n");
>     return  0;
> }
>
> compiled with my valac 0.26.1, the result segfaults in line 4.
> I can't imagine, this is intended behaviour.
>
> Of course, the proper way to go for line 4 would be something like
>
>     string x = "foobar%lld".printf(test);
>
> Nevertheless i wonder, why the code segfaults, shouldn't there rather
> be a type conversion error at compile time?
>
> Sorry, i don't have a more recent 0.27 or 0.26.2 compiler at hand.
>
>
> TIA, Grindhold
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-- 
--Andre Masella<andre masella name>
http://www.masella.name/