Re: [PATCH] removal of "static foo = 0" from drivers/ide (test11)

From: J . A . Magallon (jamagallon@able.es)
Date: Fri Nov 24 2000 - 18:13:51 EST

On Thu, 23 Nov 2000 12:01:53 Rusty Russell wrote:
>
> What irritates about these monkey-see-monkey-do patches is that if I
> initialize a variable to NULL, it's because my code actually relies on
> it; I don't want that information eliminated.
>

What I understood from the previous answer from Tigran is that you can
avoid initializations to ZERO or NULL, because the BSS is zeroed (ie, all
variables you declare static os global in a module are zeroed) at
kernel start.

As I understand from compiler working, if you put a statement like
int a = 0;
int b = 0;
all variables that have an initial value are stored contiguous in the
data segment of the executable and an image of their initial values has
to be stored with the binary. So if a program like

int a[16384];
int main() {}

gives a binary of 13k, if you write it as

int a[16384] = {0};
int main() {}

it has to store the 64k of a, just to put a 0 in the first place and
make the exec size to 78k.

ANSI rules for C say that uninitialized vars get a 0, but you can't trust
on the ANSI behaviour of a compiler.

Obviuosly, you have to leave your initializations to 7 or -1 in place. 

-- 
Juan Antonio Magallon Lacarta                                 #> cd /pub
mailto:jamagallon@able.es                                     #> more beer

Linux 2.2.18-pre23-vm #3 SMP Wed Nov 22 22:33:53 CET 2000 i686 unknown

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/

This archive was generated by hypermail 2b29 : Thu Nov 30 2000 - 21:00:12 EST