undefined reference to `memset'

[Peter Wemm]

On Wednesday 23 March 2005 01:48 pm, Vinod Kashyap wrote:
> If any kernel module has the following, or a similar line in it:
> -----
> char x[100] = {0};
> -----
> building of the GENERIC kernel on FreeBSD 5 -STABLE for amd64
> as of 03/19/05, fails with the following message at the time of
> linking: "undefined reference to `memset'".
>
> The same problem is not seen on i386.
>
> The problem goes away if the above line is changed to:
> -----
> char x[100];
> memset(x, 0, 100);
> -----
>
> Adding CFLAGS+=-fbuiltin, or CFLAGS+=-fno-builtin to
> /sys/conf/Makefile.amd64 does not help.
>
> Anyone knows what's happening?

Something fishy is going on.  I've tried this on both 5.x and 6.0 and 
both systems created a bss object called 'x', not something that called 
memset.

For example:
peter at fb5-amd64[9:17pm]/home/src/sys/modules/twe-21# nm obj/twe.ko | 
grep x
                 U busdma_lock_mutex
                 U sysctl_ctx_free
                 U sysctl_ctx_init
0000000000000080 b x
peter at fb5-amd64[9:17pm]/home/src/sys/modules/twe-22# nm obj/twe.ko | 
grep memset
peter at fb5-amd64[9:17pm]/home/src/sys/modules/twe-23# 

I wondered if it might be because of something like -O2 (don't do that) 
or no -O at all, but I couldn't make it happen even then.
-- 
Peter Wemm - peter at wemm.org; peter at FreeBSD.org; peter at yahoo-inc.com
"All of this is for nothing if we don't go to the stars" - JMS/B5