undefined reference to `memset'

[Sean McNeil]

On Thu, 2005-03-24 at 13:49 -0800, David O'Brien wrote:
> Please don't top-post -- it destroys context.  [Format recovered]
> 
> On Thu, Mar 24, 2005 at 12:46:41PM -0800, Vinod Kashyap wrote:
> > > On Thu, Mar 24, 2005 at 06:05:17PM +1100, Peter Jeremy wrote:
> > > > On Wed, 2005-Mar-23 13:48:04 -0800, 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);
> > > > >-----
> > > > 
> > > > Can you post a complete (compilable) example please.
> > > 
> > > Vinod can you please post a complete compilable example?
> > > It is impossible to get anything done about your issue without stand
> > > alone test code.
> > Ok, make sure you have 'device twa' in your kernel configuration
> > file, and apply these patches to /sys/dev/twa/twa.c.
> > This patch causes the problem:
> 
> "stand alone" means a single foo.c file that shows the problem you want
> fixed.
> I cannot submit a GCC bug report with a tarball of the entire FreeBSD
> kernel.

I've taken the liberty to write up an example here.  Not sure if this is
a bug or not:

cc -O -pipe -c -fno-builtin -ffreestanding memset_bug.c

Take a look at what is generated:

objdump --disassemble memset_bug.o

You'll see that instead of performing the inline code generation for
memset, the compiler generates a call to memset in the case of the
assignment of {0}.

memset_bug.c:

#include <sys/types.h>

static __inline void *
memset(void *b, int c, size_t len)
{
	char *bb;

	if (c == 0)
		bzero(b, len);
	else
		for (bb = (char *)b; len--; )
			*bb++ = c;
	return (b);
}

void bug (void)
{
    int buf[100] = { 0 };

    memset (buf, sizeof(buf), 0);
    printf ("%d\n", buf[0]);
}

Attached as well.

Cheers,
Sean