CODEWITHSUNDEEP
linuxmacossizeosx-leopardunix
hyperbolic
hyperbolic

Reputation: 49

Data section size in "size" command on Mac

Given the following output of the "size" command on Mac OS X 10.5 on an small executable, what is the value under __DATA? Is it the uninitialized data segment size or initialized data segment size? What I find confounding is that this value (nor the rest of the values) does not seem to change whether I initialize (the one and only) global array in the program or not.

I guess this command works differently on Linux and Mac?

__TEXT  __DATA  __OBJC  others  dec hex
4096    4096    0   4294971392  4294979584  100003000

Upvotes: 3

Views: 1105

Answers (2)

Ken Thomases
Ken Thomases

Reputation: 90671

All statics and globals are initialized, it's just a question of whether they are initialized to zero or some other value. Variables initialized to zero go into the __bss section of the __DATA segment. Other variables will go into other sections of the __DATA segment.

Upvotes: 1

Pavan Manjunath
Pavan Manjunath

Reputation: 28565

On linux, the format is

   text    data     bss     dec     hex filename
   1281     520      32    1833     729 a.out

BSS is the size in bytes of the zero initialized globals and local statics. I verified and they(data, bss etc) are changing appropriately with change in the number of variables and their initialized values.

One thing to note is, size without any parameters automatically chooses a.out in the CWD.

I am totally unaware of things in Mac. My guess is __OBJC = BSS . Also check how are you invoking the size command

Upvotes: 1

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