Re: casting doubles to ints

Hi Iain, (Yes, this subject has me sending a message to the list again instead of lurking, and I should be back with some internals stuff again soon, hehe. :^)) ----- Original Message ----- From: "Iain Lewis" Sent: Wednesday, February 04, 2009 Subject: [PHP-DEV] casting doubles to ints > Hello all, > > I wanted to suggest back porting the behaviour of the DVAL_TO_LVAL macro > from zend_operators.h from 5.3 to 5.2, and wondered whether people > thought this was a good idea or not? > > The reason I want to do this is that while writing some tests, I noticed > that the behaviour of casting a float to an int is a bit > counter-intuitive on 64bit platforms for PHP 5.2. It looks as though > this has been fixed in 5.3, and it would seem like a good idea to put > this change back to 5.2 as well. From a personal point of view, it would > mean I could write one test that would work on both 5.2 and 5.3, but it > also seems like a sensible change, as the current behaviour is > non-obvious. The change would cause some current tests to break, but I > am happy to do the work to fix those up. NOOOO, please. :-) In fact, I thought maybe your message was complaining about the 5.3 changes. I was suggesting reverting 5.3 to 5.2's behavior at the very least -- see my "DVAL_TO_LVAL() change, different behavior" thread [1] from last year for the reasons. It breaks long-time behavior (overflow-wise), and isn't even consistent with how it works. I was thinking there will be some breakage, bug reports, etc. as 5.3 is used more, if others are doing stuff like my examples showed. *shrug* In addition to my suggestion of going back to the behavior of 5.2 and earlier, I think DVAL_TO_LVAL() can be updated to ensure consistent, reliable overflow behavior on all systems -- it seems like it has been on the majority, but a simple (long) cast of the double (when out of range) in C is implementation-defined, so depending... Anyway, I didn't get to test my idea yet, but will get to it soon! The thing that I think was originally trying to be fixed (large function args) can be done easily in zend_parse_parameters() for those desired use cases. [1] http://marc.info/?t=120799728700001&r=1&w=2 > This is how a few expressions get evaluated at the moment. Changing the > macro would make the 5.2 behaviour match 5.3 > > Expression 5.3 (RHEL5-64) 5.2 (RHEL5-64) > > (int) (PHP_INT_MAX) 9223372036854775807 9223372036854775807 > (int) (PHP_INT_MAX + 1) 9223372036854775807 -9223372036854775808 > (int) (PHP_INT_MAX + 1000) 9223372036854775807 -9223372036854775808 > (int) (PHP_INT_MAX + 10000) 9223372036854775807 -9223372036854765568 > > Does this seem like a good change? - Matt