🚀 go-pugleaf

In article <30e5c15b.10973056@nntp.ix.netcom.com>, miker3@ix.netcom.com 
says...

[snip]

>As your program stands, it crashes because you are dereferencing a
>null pointer.  That results in undefined behavior, so you can't count
>on anything.  In principle, the compiler could reorder the calls.

True, a  compiler could detect it and produce code to print only
one message eg.
"Due to the problem with the programmer this program refuses to run." :)
And that would be conforming. (leaving aside the quality of implementation)


>However, there are conforming programs for which calling the function
>after the printf() would result in different output (e.g., if it does
>any output to stdout), and it would be illegal for the compiler to
 ^^^^^^^^^^^^^^^^^^^^^
That would make the two functions dependent.

>change the order of the calls for such programs.  It's unlikely that a
>compiler could tell the difference, so I doubt if the order of the
>function calls would be changed.

As Jutta Degener (jutta@cs.tu-berlin.de) posted, the minimal requrements
do allow reordering (including function calls) of statemets with no
dependencies, and do regulate interactive I/O. It's just enough
to allow aggresive optimizations, and keep the resulting code
conforming. An undefined behaviour may show the optimizations, but
then the program itself is 'non-conforming' (not to use word "garbage":),
so it doesn't matter.

>Michael M Rubenstein

Thank you,

B. Wiecek
wiecek@ee.ualberta.ca
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