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To: "'Dmitry Stogov'" <dmitry@php.net>,
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	"'Nikita Popov'" <nikita.ppv@gmail.com>,
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Date: Fri, 21 Aug 2015 10:41:25 +0200
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Subject: Overflow checks and integral vars comparison
From: anatol.php@belski.net ("Anatol Belski")

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