Re: GCC not doing the correct thing?

FROM : Cameron Hayne
DATE : Mon Nov 11 23:31:30 2002

On 9/11/02 4:35 pm, "Domain Administrators" <<email_removed>> wrote:

> Forgive me for my impertinence, but if the example code were to be
> "undefined" by definition we would all be in a lot of trouble.

Since this point seems to need a lot of emphasis, allow me to essentially
repeat what Clark Cox has said:
The C++ standard says that the order of evaluation of sub-parts of an
expression is undefined unless explicitly mentioned. And the section on
multiplication does not define the order of evaluation of the left and
right-hand operands in a multiplication. Same thing for addition, etc.
Hence the value of (*ptr++) * (*ptr++) is undefined since it depends on the
order of evaluation of the two multiplicands.

Some people seem to think that the "left-associativity" of multiplication
means that the left operand gets evaluated before the right one. It doesn't
mean that - it merely means that x*y*z is to be evaluated as (x*y)*z. It
says nothing about the order of evaluation of the values x,y,z.

--
Cameron Hayne (<email_removed>)
Hayne of Tintagel
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