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A comment on Pitfalls in C and C++: Unsigned Types (2011). Parent comment

Re:Pitfalls in C and C++: Unsigned Types (2011) by Someone on Wednesday September 25, 2013 @06:56PM (#6447865)
I don't see why arr[(unsigned)-1] is guaranteed to segfault. Care to explain?

Isn't it equivalent to

  * (arr + (unsigned) -1)
, which should be equivalent to

  * (arr + UINT_MAX)
On typical PC hardware with sizeof(int) == sizeof(char *) that looks like a undefined behavior case to me (maybe barring border conditions; I don't feel like thinking of all edge cases). Most C compilers choose the fastest possible path for undefined behavior cases, so I would expect this to (typically. Again, there will be border cases) be equivalent to arr[-1].

(See also http://stackoverflow.com/questions/2578455/pointer-arithmeti...)

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Re:Pitfalls in C and C++: Unsigned Types (2011) by dllthomas on Thursday September 26, 2013 @03:09AM (#6449321)
"Typical PC hardware", at least in my recent experience, has sizeof(int) == 4, sizeof(char*) == 8 and so the reason they're different should be apparent. I believe you are correct that there is no difference when they are equal.
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