RE: automatic reference to memset?

[Shaya Potter <spotter at cs dot columbia dot edu>]

It's not a kernel module problem, it was the fact that memset isn't a
builtin in gcc 2.95 and therefore when using the gcc extension of 

char devpts[15] = "/dev/pts" it requires memset therefore there's a
undefined symbol that has to be resolved.

fixing it is easy enough, and since gcc 2.96 and 3.2 have it as a
builtin, not even a problem for those.

On Fri, 2002-09-27 at 13:52, Douglas Richardson wrote:
> To build a linux kernel module you must define a few things and include a
> few header files.
> 
> The book "Linux Device Drivers" will show you how to write a simple module
> quickly. You can view the book in PDF form at
> http://www.xml.com/ldd/chapter/book/bookindexpdf.html.
> 
> Douglas Richardson.
> 
> -----Original Message-----
> From: Shaya Potter [mailto:spotter@cs.columbia.edu]
> Sent: Thursday, September 26, 2002 23:55
> To: gcc-bugs@gcc.gnu.org
> Subject: automatic reference to memset?
> 
> 
> with the gcc included in debian ("2.95.4" a "debian prerelease") causes
> gcc to cause a reference to memset to be automatically included.  Which
> is very bad as this code is meant to be a snippet of code in a kernel
> module, where obviously memset wont resolve.  I remove the devpts
> decleration than there is no problem, so I'm guessing its related to the
> fact that I declare it to be size 15 and I initilize it to a value. 
> However, with red hat's gcc "2.96" and debian's gcc-3.2 (also called a
> "debian prerelease") the code seems to compile normally.
> 
> this is driving me crazy, so if anyone can help I'd appreciate it
> 
> the sample code
> 
> extern int original_open(char *, int, int);
> 
> int zap_hook_open(char *filename, int flags, int mode)
> {
>         unsigned int fd;
>         char devpts[15] = "/dev/pts/";
>         char pts[4];
> 
>         fd = original_open(filename, flags, mode);
> 
>         return fd;
> }
> 
> the .s produced
> 
>         .file   "test.c"
>         .version        "01.01"
> gcc2_compiled.:
> .section        .rodata
> .LC0:
>         .string "/dev/pts/"
> .globl memset
> .text
>         .align 4
> .globl zap_hook_open
>         .type    zap_hook_open,@function
> zap_hook_open:
>         pushl %ebp
>         movl %esp,%ebp
>         subl $40,%esp
>         movl $.LC0,%eax
>         movl (%eax),%edx
>         movl %edx,-20(%ebp)
>         movl 4(%eax),%edx
>         movl %edx,-16(%ebp)
>         movzwl 8(%eax),%eax
>         movw %ax,-12(%ebp)
>         leal -10(%ebp),%eax
>         addl $-4,%esp
>         pushl $5
>         pushl $0
>         pushl %eax
>         call memset
>         addl $16,%esp
>         addl $-4,%esp
>         movl 16(%ebp),%eax
>         pushl %eax
>         movl 12(%ebp),%eax
>         pushl %eax
>         movl 8(%ebp),%eax
>         pushl %eax
>         call original_open
>         addl $16,%esp
>         movl %eax,-4(%ebp)
>         movl -4(%ebp),%edx
>         movl %edx,%eax
>         jmp .L2
>         .p2align 4,,7
> .L2:
>         leave
>         ret
> .Lfe1:
>         .size    zap_hook_open,.Lfe1-zap_hook_open
>         .ident  "GCC: (GNU) 2.95.4 20011002 (Debian prerelease)"