Sizeof Operator Implementation

hiren · 09-28-2004, 02:29 AM

Dear Memebers,

I want to know how the Sizeof Operator is implemented and also What does matter when deciding the size of Interger? Why it is 2 bytes in Windows and 4 bytes in Linux.

Could anyone help me out? I have tried searching on Net but couldn't able to find out.

Thank you,
Hiren Gajjar.

ananthbv · 09-28-2004, 04:02 AM

hi, i think sizeof() is implemented somewhat like this

Code:

#define sizeof(x)  ((void *)(&x + 1) - (void *)(&x))

and the size of an int depends on the hardware, particularly the Arithmetic and Logic Unit(ALU).

hiren · 09-28-2004, 04:14 AM

I don't think so. Because sizeof operator will also accept Data types.. like sizeof(int), sizeof(char)...

Thanks.
Hiren Gajjar.

ananthbv · 09-28-2004, 04:30 AM

yeah, that occured to me later

, maybe datatypes are checked for before variables.

Sadrul · 09-28-2004, 10:32 AM

`int' is 2 bytes in Turbo C/C++, because TC is a 16-bit compiler. if you compile in Visual C (which is a 32-bit compiler), you will see that `int' is 4 bytes. all compilers (that i know of) in linux are 32 bit compilers. so `int' always shows 4 bytes in gcc.

i don't know much about the implementation of the `sizeof' operator.

-- Adil