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rfc:typed_properties_v2 [2019/01/07 14:48]
nikic Add errata: inc/dec overflow |
rfc:typed_properties_v2 [2019/01/11 16:16] (current)
nikic Implemented |
| * Implementation: https://github.com/php/php-src/pull/3313 | * Implementation: https://github.com/php/php-src/pull/3313 |
| * Discussion: https://externals.io/message/102333 and https://externals.io/message/103148 | * Discussion: https://externals.io/message/102333 and https://externals.io/message/103148 |
| * Status: Accepted | * Status: Implemented (in PHP 7.4) |
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| ===== Introduction ===== | ===== Introduction ===== |
| ==== Incrementing/decrementing beyond the maximal/minimal value ==== | ==== Incrementing/decrementing beyond the maximal/minimal value ==== |
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| When a value is incremented beyond ''PHP_INT_MAX'' or decremented beyond ''PHP_INT_MIN'' it is converted into a floating-point value and incremented/decremented as a floating-point value. Additionally, under PHPs type verification rules (both strict //and// weak), assigning an out-of-range floating point value to an integer is illegal. | When a value is incremented beyond ''PHP_INT_MAX'' or decremented beyond ''PHP_INT_MIN'' it is converted into a floating-point value and incremented/decremented as a floating-point value. Additionally, under PHP's type verification rules (both strict //and// weak), assigning an out-of-range floating point value to an integer is illegal. |
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| As stated, this would result in the following peculiar behavior: Incrementing an ''int'' property past the maximal value, would always be an error, because ''(float)PHP_INT_MAX + 1'' exceeds the integer range. However, decrementing an ''int'' property past the minimal value would only error on 32-bit systems. The reason is that on 64-bit systems ''(float)PHP_INT_MIN - 1'' is the same as ''(float)PHP_INT_MIN'', which is accurately representable as a double-precision floating point number and as such can be assigned back to an ''int'' property without error. | As stated, this would result in the following peculiar behavior: Incrementing an ''int'' property past the maximal value would always be an error, because ''(float)PHP_INT_MAX + 1'' exceeds the integer range. However, decrementing an ''int'' property past the minimal value would only error on 32-bit systems. The reason is that on 64-bit systems ''(float)PHP_INT_MIN - 1'' is the same as ''(float)PHP_INT_MIN'', which is accurately representable as a double-precision floating point number and as such can be assigned back to an ''int'' property without error. |
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| As such, we would always generate an error on increment/decrement overflow, apart from the case of decrements on 64-bit systems. | As such, we would always generate an error on increment/decrement overflow, apart from the case of decrements on 64-bit systems. |
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| To avoid this, we instead define that incrementing/decrementing an ''int'' property past the maximal/minimal value always generated an error. It should be noted that this only affects the ''++'' and ''--'' operators. Overflows caused by other means are not handled specially. | To avoid this, we instead define that incrementing/decrementing an ''int'' property past the maximal/minimal value always generates an error. It should be noted that this only affects the ''++'' and ''%%--%%'' operators. Overflows caused by other means are not handled specially. |
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| ===== Changelog ===== | ===== Changelog ===== |