> -----Original Message-----
> From: Stuart Hughes [SMTP:[EMAIL PROTECTED]]
> Sent: Wednesday, February 23, 2000 6:39 AM
> To: David Schleef
> Cc: rtlinux
> Subject: Re: [rtl] Problem loading modules
>
> David Schleef wrote:
> >
> > On Tue, Feb 22, 2000 at 12:51:11PM +0000, Stuart Hughes wrote:
> > >
> > > Note also the following compiler feature:
> > >
> > > If have in your RT code:
> > >
> > > char buf[12] = "mystring";
> > >
> > > You get an error, due to an implicit call to memset.
> >
> > Nope. gcc-2.7.2.3 outputs assembly instructions that perform
> > the memcpy, even with very long strings.
>
> Hi Dave,
>
> That's weird, this is what I get (gcc version 2.7.2.3). If I compile
> the code below using:
>
> cc -O2 -g -D__KERNEL__ -DMODULE -c -o para_mod.o para.c
>
> and then try to insmod para_mod.o, I get the following:
>
> ./para_mod.o: unresolved symbol memset
>
> If I comment out the first version and uncomment the second, everything
> works ???
>
> Any ideas ??
>
[Norm Says:]
The first form ( char buff[12]="test"; ) creates the string "test"
somewhere in memory and then when the function init_module is entered, space
is made on the stack for the buf[] array and the string is copied from the
string to the array.
The second form ( char *buff="test";) also creates the string "test"
in memory -- probably in the same place as the first -- but when the
function init_module is entered, just the space for a char-pointer is made
on the stack and the pointer is initialized with the addess of the string;
no copying is done, just the storing of a "numeric" data item on the stack
(possibly even a push of immediate data).
It's all perfectly logical.
Norm
> Regards, Stuart
>
>
> // System headers.
> #include <linux/module.h>
> #include <asm/io.h>
>
> int init_module(void)
> {
> char buf[12] = "test"; // fails, calls implicit memset
> // char *buf = "test"; // Okay
> printk(buf);
>
> return 0;
> }
>
> void cleanup_module(void)
> {
> }
>
>
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