pointer question

[tomtetlaw]

Is there a way to ensure that all un-initialized pointers automatically have the address 0x00000000? Sometimes they're being set to other addresses but still being unitialized, and they pass tests like if(!ptr), causing an unhandled access violation error.

[gerard4143]

Just set the pointer to NULL.

void *vptr = (void*)NULL;

You should get into a habit of initializing all pointers to NULL and all freed pointers to NULL.

[tomtetlaw]

I'm using a pointer to a pointer, to have an array of pointers, and a new item in the array only gets added when the (!ptr) test returns true, which it doesn't because the address of the pointer isn't 0x00000000. Here, I'll post some code:

if (!m->verts)
	{
		m->verts = malloc (sizeof(mvertex_t));
		Q_memset (m->verts, 0, sizeof(mvertex_t));
	}

	if (!m->verts[m->numverts])
	{
		m->verts[m->numverts] = malloc (sizeof(mvertex_t) * m->numverts+1);
		Q_memset (m->verts[m->numverts], 0, sizeof(mvertex_t));
	}

In this code, if m->verts is NULL (i set it to null before) then it gets initialized and is all good. But I can't set m->verts[m->numverts] to NULL because it hasn't been allocated yet and for some reason it's getting set to 0xfdfdfdfd.

[Narue]

>Sometimes they're being set to other addresses but still being unitialized, and
>they pass tests like if(!ptr), causing an unhandled access violation error.
That's the whole point, genius. If you're trying to use an uninitialized pointer, that's a Bad Thing™, and it should be immediately fatal as it's a programming error.

>But I can't set m->verts[m->numverts] to NULL because it hasn't been
>allocated yet and for some reason it's getting set to 0xfdfdfdfd.
I fail to see why you can't set m->verts[m->numverts] to NULL . Your statement suggests a misunderstanding of the difference between a pointer and the memory it points to.

[tomtetlaw]

>That's the whole point, genius.
I know that, it's just sometimes m->verts[m->numverts] is being set to 0x00000000 and sometimes it isn't, and it is still unitialized.

I can't set m->verts[m->numverts] to NULL because at the point before if (!m->verts[m->numverts]) , m->verts[m->numverts] doesn't exist as m->verts is only malloc'd to a size of (sizeof(mvertex_t)*m->numverts-1). Only in that if statement does m->verts[m->numverts] exist.

[Narue]

>I can't set m->verts[m->numverts] to NULL because at the point before
>if (!m->verts[m->numverts]) , m->verts[m->numverts] doesn't exist
You do realize how ridiculous this sounds, right? "I can't set the object to null because the object doesn't exist when I test it for null". If your code is as whack as I'm seeing and you're describing, it's a wonder it works even some of the time.

[tomtetlaw]

Oh. I realise now, I feel like an idiot. I fixed the problem anyway though. I just, instead of using a pointer to a pointer as an array of pointers, I use one pointer as an array of values.