No nullptr check in cowdata - crash to desktop

[ShlomiRex]

Godot version

v4.2.dev.custom_build.ba54c3455

System information

macOS M1

Issue description

In cowdata.h line 314:

godot/core/templates/cowdata.h

Line 314 in 571cd0e

*_get_size() = p_size;

We can see:

*_get_size() = p_size;

The function _get_size() may return nullptr:

	_FORCE_INLINE_ uint32_t *_get_size() const {
		if (!_ptr) {
			return nullptr;
		}

		return reinterpret_cast<uint32_t *>(_ptr) - 1;
	}

I discovered this when investigating the issue: #63534

This is the cause of the issue and the cause of the crash.

Since I don't understand Copy-On-Write logic, I don't know how to fix it. So I leave it to you guys.

Steps to reproduce

1. Get Editing Tileset Causes Crash to desktop #63534 project (download the example)
2. Open (double click in godot editor)res://godot_4_alpha_12_tileset_issue_2.log
3. Crash into desktop

Minimal reproduction project

Get #63534 project (download the example)

[AThousandShips]

I'm not sure how this could happen as all the paths leading to *_get_size() = p_size; are null checked?

[AThousandShips]

Might know, will do some checking later today

[ShlomiRex]

I'm not sure how this could happen as all the paths leading to *_get_size() = p_size; are null checked?

I did small change to see the result of _get_size() and indeed it's zero-pointer:

[AThousandShips]

I've identified the error, looking into a fix