Re: [PATCH] C undefined behavior fix

I don't have the ANSI standard in front of me, isn't it the case that
casting a pointer to/from an integer is implementation defined, rather
than undefined, so people who need to do pointer arithmatic that relies on
the machine's memory map can do
 (void *)(((int)p) + some_magic_number)

and have some sort of assurance that the compiler won't mess with it?

-JKL


On Thu, 3 Jan 2002, David Woodhouse wrote:

(cc list trimmed)

alan@lxorguk.ukuu.org.uk said:

quoted

 If you want a strcpy that isnt strcpy then change its name or use a
different language 8)

The former is not necessarily sufficient in this case. You've still done the
broken pointer arithmetic, so even if the function isn't called strcpy() the
compiler is _still_ entitled to replace it with a call to memcpy() or even
machine_restart() before sleeping with your mother and starting WW III.

Granted, it probably _won't_ do any of those today, but you should know
better than to rely on that.

What part of 'undefined behaviour' is so difficult for people to understand?

--
dwmw2

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