Le 2010-08-22 à 17:07, Walter Bright a écrit :
> Sean Kelly wrote:
>> I think it depends on how the compiler dereferences fields of an object. GCC
>> on OSX if I have a null ptr to a struct and I try to access a field through
>> it I'll get the data at 0x4 or wherever and the code will keep on running.
>> Actual segfaults happen depressingly rarely.
>
> On Windows, the entire first 64K of address space is reserved by the OS, and
> any attempt to access it results in a seg fault. I'm very surprised that OS X
> would not do the same.
A quick test with DMD on OS X reveals that reading anything below the first 4K
of the address space causes a segfault.
For instance, reading member b of a null pointer to this struct will not cause
a segfault:
struct S {
ubyte[4*1024] a;
ubyte b;
}
S* s = null;
ubyte c;
@safe void main() {
c = s.b;
}
Remove one byte from array a and you have a segfault.
--
Michel Fortin
[email protected]
http://michelf.com/
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