Re: in standard C it is impossible to write a correct program. Why?

richard@xxxxxxxxxxxxxxx (Richard Tobin) writes:
In article <pan.2009.09.02.18.09.51.0@xxxxxxxxxxx>,
Nobody <nobody@xxxxxxxxxxx> wrote:

Does the lcc-win documentation provide sufficient information to determine
the last arithmetic operation performed when evaluating a particular
expression?

I would have thought it was far less ambiguous to provide a built-in
"function" (probably a macro):

check_overflow(expression)

which returns true if overflow occurs during the evaluation of the
expression. This doesn't require any odea of "last operation', makes
no assumption about overflow being indicated by a flag, and allows the
compiler to generate different (perhaps slower) code in cases where
overflow needs to be checked for.

For example:

You forgot these lines:

long long int a=~0u>>1, b=a;
short int c;

if(check_overflow(c = a+b))
fprintf(stderr, "sorry, overflow in addition\n");

But there was no overflow in addition, the overflow was in the
attempt to assign the greater-than-short value to the short variable.

Phil
--
If GML was an infant, SGML is the bright youngster far exceeds
expectations and made its parents too proud, but XML is the
drug-addicted gang member who had committed his first murder
before he had sex, which was rape. -- Erik Naggum (1965-2009)
.

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