SHORT Re: Suggestion: "fix" assert(obj)

[Walter Bright]

Georg Wrede wrote:
> Walter Bright wrote:
>> Kristian Kilpi wrote:
>>
>>> The problem is that
>>>
>>>   assert(obj);
>>>
>>> does not first check if 'obj' is null.
>>
>>
>> Yes it does, it's just that the hardware does the check, and gives you 
>> a  seg fault exception if it is null.
> 
> Asserts were INVENTED to *avoid segfaults*.

I don't know when assert first appeared. But I first encountered them in 
the 80's, when the most popular machine for programming was the x86. The 
x86 had no hardware protection. When you wrote through a NULL pointer, 
you scrambled the operating systems, and all kinds of terrible, 
unpredictable things ensued. Asserts were used a lot to try and head off 
these problems.

Enter the 286. What a godsend it was to develop in protected mode, when 
if you accessed a NULL pointer you got a seg fault instead of a 
scrambled system. Nirvana! What was even better, was the debugger would 
pop you right to where the problem was. It's not only asserts done in 
hardware, it's asserts with:

1) zero code size cost
2) zero runtime cost
3) they're there for every pointer dereference
4) they work with the debugger to let you know exactly where the problem is

Seg faults are not an evil thing, they're there to help you. In fact, 
I'll often *deliberately* code them in so the debugger will pop up when 
it hits them.