Linux assembly; bss section memory initialized to 0?

Question

In tests I have run the memory in the bss section of my programs has always been initialized to zero before I write anything there. Is this coincidental, or is the system "cleaning" these memory pages before handing them to me? I am using the nasm assembler on Ubuntu (if that possibly makes a difference).

Answer 1

Your application's executable file(ELF) has a BSS section's size information, when it starts up, kernel allocate a block of memory for BSS section, and clean it to 0. This defined by ABI(Application Binary Interface), so you needn't worry about there are different on different machine.