Hi Marcus, On Thu, Oct 26, 2017 at 1:09 AM, Marcus Denker <marcus.denker@inria.fr> wrote:

On 26 Oct 2017, at 10:05, Denis Kudriashov <dionisiydk@gmail.com> wrote:

Hi.

Question from discord, why:

2017 sizeInMemory = 0

?

Looks like a bug, but maybe there is some reason for this.

#sizeInMemory only takes into account object header size and the size of the object itself.

sizeInMemory is also ignorant of details such as the padding of objects to 64-bits in both 32-bit and 64-bit Spur, the overflow header when there are more than 254 slots, etc. siseInMemory should really be implemented like this: Object>>sizeInMemory ^self class isVariable ifTrue: [self class byteSizeOfInstanceOfSize: self basicSize] ifFalse: [self class byteSizeOfInstance] where the subsidiary definitions are Behavior>>byteSizeOfInstance "Answer the total memory size of an instance of the receiver." <primitive: 181 error: ec> self isVariable ifTrue: [^self byteSizeOfInstanceOfSize: 0]. self isImmediateClass ifTrue: [^0]. self primitiveFailed byteSizeOfInstanceOfSize: basicSize "Answer the total memory size of an instance of the receiver with the given number of indexable instance variables." <primitive: 181 error: ec> self isVariable ifTrue: "If the primitive overflowed answer a close approximation" [(basicSize isInteger and: [basicSize >= 16r1000000]) ifTrue: [^2 * (self byteSizeOfInstanceOfSize: basicSize + 1 // 2) - (self byteSizeOfInstanceOfSize: 0)]] ifFalse: [basicSize = 0 ifTrue: [^self byteSizeOfInstance]]. self primitiveFailed

A small-integer is encoded in the pointer, so it has no size in itself, only the object pointing to it needs space for the pointer, just like for normal object.

As are Characters, and in 64-bits the single-precision range of the double-precision floats: { SmallInteger maxVal sizeInMemory. (SmallInteger maxVal + 1) sizeInMemory. 1.0e38 sizeInMemory. 1.0e39 sizeInMemory. $a sizeInMemory } in 64 bit is #(0 16 0 16 0) in 32 bit is #(0 16 16 16 0) The overflow header is revealed by (251 to: 258) collect: [:n| (Array new: n) sizeInMemory] in 64 bit is #(2016 2024 2032 2040 2056 2064 2072 2080) in 32 bit is #(1016 1016 1024 1024 1040 1040 1048 1048) _,,,^..^,,,_ best, Eliot