Re: Overflow checks and integral vars comparison

Maybe I'm missing something here, but how do these macros detect overflow exactly? If the check is done on the actual result and not the operands then it's not a good overflow check. Additionally, why wouldn't overflow checks be needed on 32-bit architecture, or any other architecture for that matter? Integers can overflow there too. On Fri, Aug 21, 2015 at 4:41 AM, Anatol Belski <anatol.php@belski.net> wrote: > Hi, > > Resending this as missed internals at the start. > > I was lately rethinking some part of the 64-bit RFC, and also seeing now > Jakub's work on catching overflows in ext/openssl and Matt Williams > suggestions on it (which was going a bit more global over it). So I came up > with these macros with two goals > > - standardize the overflow checks > - do actualy checks only on architectures where it's needed > - simplify the checks where external libs (openssl, libxml, etc.) use firm > datatypes like int > > #if SIZEOF_INT == SIZEOF_ZEND_LONG > # define ZEND_LONG_INT_OVFL(zl) (0) > # define ZEND_LONG_INT_UDFL(zl) (0) > #else > # define ZEND_LONG_INT_OVFL(zlong) ((zlong) > (zend_long)INT_MAX) # define > ZEND_LONG_INT_UDFL(zlong) ((zlong) < (zend_long)INT_MIN) #endif > > #define ZEND_SIZE_T_INT_OVFL(size) ((size) > (size_t)INT_MAX) > > So having it like > > If (ZEND_LONG_INT_OVFL(x)) { > return; > } > > Compiler would eliminate the branch automatically on 32-bit and ILP64. > > Some other macros to do signed/unsigned comparison, these can be extended. > > #define ZEND_SIZE_T_GT_ZEND_LONG(size, zlong) ((zlong) < 0 || (size) > > (size_t)(zlong)) #define ZEND_SIZE_T_GTE_ZEND_LONG(size, zlong) ((zlong) < > 0 > || (size) >= (size_t)(zlong)) #define ZEND_SIZE_T_LT_ZEND_LONG(size, zlong) > ((zlong) >= 0 && (size) < (size_t)(zlong)) #define > ZEND_SIZE_T_LTE_ZEND_LONG(size, zlong) ((zlong) >= 0 && (size) <= > (size_t)(zlong)) > > IMHO these and maybe more are missing after the 64-bit RFC. Do you think > they would make sense? Or would make sense now, or later in master? > > Thanks > > Anatol > > > -- > PHP Internals - PHP Runtime Development Mailing List > To unsubscribe, visit: http://www.php.net/unsub.php > >