On Sunday, 2 March 2014 at 20:45:42 UTC, Steven Schveighoffer wrote:
> On Sun, 02 Mar 2014 15:44:47 -0500, Namespace <rswhite4@googlemail.com> wrote:
>
>> On Sunday, 2 March 2014 at 20:21:51 UTC, Steven Schveighoffer wrote:
>>> On Sat, 01 Mar 2014 09:57:44 -0500, Namespace <rswhite4@googlemail.com> wrote:
>>>
>>>>
>>>> I tried to enable the printf's in rt/lifetime.d (e.g.: https://github.com/D-Programming-Language/druntime/blob/e47a00bff935c3f079bb567a6ec97663ba384487/src/rt/lifetime.d#L1125) to see what happens if I/the GC delete an array. But I see no output, no matter what I try to allocate/deallocate.
>>>
>>> Enabling debugging code in druntime is really hard. I remember struggling with that when I was changing the array append code. It does work when you get it right...
>>>
>>> -Steve
>>
>> Great... :D I have no idea how. :P Should I recompile phobos also? Or try something special...?
>
> You HAVE to recompile phobos, because druntime is statically included inside it ;)
>
> -Steve

Ahh.. I thought it is enough to recompile druntime... :)

It's working now, I get all my debug infos I need.
But: I have absolutly no idea how to get the correct TypeInfo in rt_finalize2. The ClassInfo is identified by casting the void* pointer to a void** and then cast this void** to ClassInfo*. But for other TypeInfos this weird trick doesn't work. How can I extract the correct TypeInfo from this void**? :P

On Monday, 3 March 2014 at 02:44:09 UTC, Namespace wrote:
> It's working now, I get all my debug infos I need.
> But: I have absolutly no idea how to get the correct TypeInfo in rt_finalize2. The ClassInfo is identified by casting the void* pointer to a void** and then cast this void** to ClassInfo*. But for other TypeInfos this weird trick doesn't work. How can I extract the correct TypeInfo from this void**? :P

I get the real TypeInfo (not sure if this was intended this way) and in my test base it works! But in druntime I get the weird error:
src\rt\lifetime.d(1256): Error: variable a1 used before set

----
    if (gc_getAttr(p) & BlkAttr.APPENDABLE)
    {
        void[] a1 = *cast(void[]*) ppv;
        //printf("len = %d\n", a1.length);

        void* p_a1 = &a1;
        void* tp = p_a1 + 12;

        TypeInfo* ti = cast(TypeInfo*) tp;

        import std.string : toStringz;
        string s = ti.toString(); // line 1256
        printf("Type = %s\n", toStringz(s));

        return;
    }
----

Any call to ti will invoke the error. Any idea why?

On Mon, 03 Mar 2014 12:03:12 -0500, Namespace <rswhite4@googlemail.com> wrote:

> On Monday, 3 March 2014 at 02:44:09 UTC, Namespace wrote:
>> It's working now, I get all my debug infos I need.
>> But: I have absolutly no idea how to get the correct TypeInfo in rt_finalize2. The ClassInfo is identified by casting the void* pointer to a void** and then cast this void** to ClassInfo*. But for other TypeInfos this weird trick doesn't work. How can I extract the correct TypeInfo from this void**? :P
>
> I get the real TypeInfo (not sure if this was intended this way) and in my test base it works! But in druntime I get the weird error:
> src\rt\lifetime.d(1256): Error: variable a1 used before set
>
> ----
>      if (gc_getAttr(p) & BlkAttr.APPENDABLE)
>      {
>          void[] a1 = *cast(void[]*) ppv;
>          //printf("len = %d\n", a1.length);
>
>          void* p_a1 = &a1;
>          void* tp = p_a1 + 12;
>
>          TypeInfo* ti = cast(TypeInfo*) tp;
>
>          import std.string : toStringz;
>          string s = ti.toString(); // line 1256
>          printf("Type = %s\n", toStringz(s));
>
>          return;
>      }
> ----
>
> Any call to ti will invoke the error. Any idea why?

Not really any clue.

But if this is in druntime, it should not be importing anything from std.

-Steve

On Monday, 3 March 2014 at 18:36:56 UTC, Steven Schveighoffer wrote:
> On Mon, 03 Mar 2014 12:03:12 -0500, Namespace <rswhite4@googlemail.com> wrote:
>
>> On Monday, 3 March 2014 at 02:44:09 UTC, Namespace wrote:
>>> It's working now, I get all my debug infos I need.
>>> But: I have absolutly no idea how to get the correct TypeInfo in rt_finalize2. The ClassInfo is identified by casting the void* pointer to a void** and then cast this void** to ClassInfo*. But for other TypeInfos this weird trick doesn't work. How can I extract the correct TypeInfo from this void**? :P
>>
>> I get the real TypeInfo (not sure if this was intended this way) and in my test base it works! But in druntime I get the weird error:
>> src\rt\lifetime.d(1256): Error: variable a1 used before set
>>
>> ----
>>     if (gc_getAttr(p) & BlkAttr.APPENDABLE)
>>     {
>>         void[] a1 = *cast(void[]*) ppv;
>>         //printf("len = %d\n", a1.length);
>>
>>         void* p_a1 = &a1;
>>         void* tp = p_a1 + 12;
>>
>>         TypeInfo* ti = cast(TypeInfo*) tp;
>>
>>         import std.string : toStringz;
>>         string s = ti.toString(); // line 1256
>>         printf("Type = %s\n", toStringz(s));
>>
>>         return;
>>     }
>> ----
>>
>> Any call to ti will invoke the error. Any idea why?
>
> Not really any clue.
>
> But if this is in druntime, it should not be importing anything from std.
>
> -Steve

Even without I get this weird error. Is this a bug?

On Mon, 03 Mar 2014 15:34:18 -0500, Namespace <rswhite4@googlemail.com> wrote:

> On Monday, 3 March 2014 at 18:36:56 UTC, Steven Schveighoffer wrote:
>> On Mon, 03 Mar 2014 12:03:12 -0500, Namespace <rswhite4@googlemail.com> wrote:
>>
>>> On Monday, 3 March 2014 at 02:44:09 UTC, Namespace wrote:
>>>> It's working now, I get all my debug infos I need.
>>>> But: I have absolutly no idea how to get the correct TypeInfo in rt_finalize2. The ClassInfo is identified by casting the void* pointer to a void** and then cast this void** to ClassInfo*. But for other TypeInfos this weird trick doesn't work. How can I extract the correct TypeInfo from this void**? :P
>>>
>>> I get the real TypeInfo (not sure if this was intended this way) and in my test base it works! But in druntime I get the weird error:
>>> src\rt\lifetime.d(1256): Error: variable a1 used before set
>>>
>>> ----
>>>     if (gc_getAttr(p) & BlkAttr.APPENDABLE)
>>>     {
>>>         void[] a1 = *cast(void[]*) ppv;
>>>         //printf("len = %d\n", a1.length);
>>>
>>>         void* p_a1 = &a1;
>>>         void* tp = p_a1 + 12;
>>>
>>>         TypeInfo* ti = cast(TypeInfo*) tp;
>>>
>>>         import std.string : toStringz;
>>>         string s = ti.toString(); // line 1256
>>>         printf("Type = %s\n", toStringz(s));
>>>
>>>         return;
>>>     }
>>> ----
>>>
>>> Any call to ti will invoke the error. Any idea why?
>>
>> Not really any clue.
>>
>> But if this is in druntime, it should not be importing anything from std.
>
> Even without I get this weird error. Is this a bug?

It sounds suspicious. Clearly, you are not accessing a1 there, and clearly a1 is set before being used.

Any chance to reduce it?

-Steve

> It sounds suspicious. Clearly, you are not accessing a1 there, and clearly a1 is set before being used.
>
> Any chance to reduce it?
>
> -Steve

I don't know. But I know that my little trick doesn't work in lifetime.d although it works locally. Here what I tried:

----
import std.stdio;

struct Foo {
	int id;
}

void main() {
	Foo[] fs;
	fs ~= Foo(45);
	fs ~= Foo(46);
	fs ~= Foo(47);
	fs ~= Foo(48);

	auto ti = typeid(fs);
	writeln("&ti = ", &ti);

	void* p = fs.ptr;

	void[] arr = *cast(void[]*) p;

	void* tp = cast(void*)((&arr) - cast(void*) 8);

	TypeInfo ti2 = *cast(TypeInfo*) tp;
	writeln(ti, " versus ", ti2);
}
----

Since rt_finalize and the GC have the same pointer as 'fs.ptr' I cast it to an array struct. From the pointer of this struct I subtract 8 (8 because of try and error until the pointer was equal the real TypeInfo pointer). This I can cast to the TypeInfo: it works. But not in lifetime.d. Was a try, but I have no idea why it doesn't work (the pointers aren't equal). An idea or alternative?