DivByZero Crash in PickSpawnPoint

[Zack]

This occurred while I was playing, so I regrettably don't have reproducible steps. I do have a stacktrace that might allow us to track down the issue.

The relevant portion:

Exception Type:        EXC_ARITHMETIC (SIGFPE)
Exception Codes:       EXC_I386_DIV (divide by zero)
Exception Note:        EXC_CORPSE_NOTIFY

Termination Signal:    Floating point exception: 8
Termination Reason:    Namespace SIGNAL, Code 0x8
Terminating Process:   exc handler [3586]

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   com.wildfiregames.0ad         	0x0000000100083deb CCmpFootprint::PickSpawnPoint(unsigned int) const + 587
1   com.wildfiregames.0ad         	0x00000001000e2d82 bool ScriptInterface::callMethodConst<CFixedVector3D, unsigned int, &(class_ICmpFootprint), ICmpFootprint, &(ICmpFootprint::PickSpawnPoint(unsigned int) const)>(JSContext*, unsigned int, JS::Value*) + 258
2   ???                           	0x0000000111f66a8e 0 + 4596329102
3   ???                           	0x000060001bf28398 0 + 105553585144728
4   ???                           	0x0000000111f685d5 0 + 4596336085
5   ???                           	0x000060001bfe2720 0 + 105553585907488
6   ???                           	0x000000010566a811 0 + 4385581073
7   com.wildfiregames.0ad         	0x000000010089a4b8 EnterBaseline(JSContext*, js::jit::EnterJitData&) + 232

From examining the code (at least at the version mirrored to GitHub) my inferance is a division by zero is only possible if:

• cmpSpawnedObstruction->GetSize() is 0
• halfSize.X is 0
• halfSize.Y is 0
• distX == -r

Before I pursue it further I thought I should check if this is already a known or solved issue.

[Freagarach]

Hi and thanks for the report :)

What version are you using? A23b, the latest trunk (from either GitHub or SVN) or the release candidate of A24? Also, is the problem reproducible? If you replay the replay, do you get the same exception? Either way, could you please upload the replay here?

[wraitii]

A23b but the code still exists unchanged in A24. Requires the obstruction to have size 0 (it crashes L197 int rows = std::max(1, (m_MaxSpawnDistance / gap).ToInt_RoundToInfinity());)

I presume you were playing with a mod?

[wraitii]

In 24945:

Fix division by 0 error in PickSpawnPoint

The spawn code should not assume that obstructions will never be 0-sized.

Reported by: Zack

Fixes #6039

Differential Revision: ​https://code.wildfiregames.com/D3583