Error when building the kernel for NSLU2: Function pmap_vac_me_user in pmap.c

[Donald T Hayford <don%donhayford.com@localhost>]

I received the following error while building the kernel for the NSLU2. 

#   compile  NSLU2_ALL/pmap.o
/home/hayford/net60/src/../tools/bin/armeb--netbsdelf-gcc -ffreestanding 
-fno-zero-initialized-in-bss -mcpu=xscale -mbig-endian -O2 -std=gnu99 
-Werror -Wall -Wno-main -Wno-format-zero-length -Wpointer-arith 
-Wmissing-prototypes -Wstrict-prototypes -Wswitch -Wshadow -Wcast-qual 
-Wwrite-strings -Wno-unreachable-code -Wno-sign-compare 
-Wno-pointer-sign -Wno-attributes -fno-strict-aliasing -Werror -Wall 
-Wno-main -Wno-format-zero-length -Wpointer-arith -Wmissing-prototypes 
-Wstrict-prototypes -Wswitch -Wshadow -Wcast-qual -Wwrite-strings 
-Wno-unreachable-code -Wno-sign-compare -Wno-pointer-sign 
-Wno-attributes -Werror -mcpu=xscale -mbig-endian -DIXP425_NPE_MICROCODE 
-I. -I/home/hayford/net60/src/sys/../common/include 
-I/home/hayford/net60/src/sys/arch -I/home/hayford/net60/src/sys 
-nostdinc -DKERNEL_BASE_EXT=0xc0000000 -DCONSPEED=115200 -DCONUNIT=0 
-DDIAGNOSTIC -DDEBUG -DMAXUSERS=8 -D_KERNEL -D_KERNEL_OPT 
-I/home/hayford/net60/src/sys/lib/libkern/../../../common/lib/libc/quad 
-I/home/hayford/net60/src/sys/lib/libkern/../../../common/lib/libc/string 
-I/home/hayford/net60/src/sys/lib/libkern/../../../common/lib/libc/arch/arm/string 
-c /home/hayford/net60/src/sys/arch/arm/arm32/pmap.c
cc1: warnings being treated as errors
/home/hayford/net60/src/sys/arch/arm/arm32/pmap.c: In function 
'pmap_vac_me_user':
/home/hayford/net60/src/sys/arch/arm/arm32/pmap.c:1677: warning: 'npv' 
may be used uninitialized in this function

The code in question is:

> static void
> pmap_vac_me_user(struct vm_page *pg, pmap_t pm, vaddr_t va)
> {
>     pmap_t kpmap = pmap_kernel();
The following is line 1677:
>     struct pv_entry *pv, *npv;
>     struct l2_bucket *l2b;
>     pt_entry_t *ptep, pte;
>     u_int entries = 0;
>     u_int writable = 0;
>     u_int cacheable_entries = 0;
>     u_int kern_cacheable = 0;
>     u_int other_writable = 0;
>
>     /*
>      * Count mappings and writable mappings in this pmap.
>      * Include kernel mappings as part of our own.
>      * Keep a pointer to the first one.
>      */
>     SLIST_FOREACH(pv, &pg->mdpage.pvh_list, pv_link) {
>         /* Count mappings in the same pmap */
>         if (pm == pv->pv_pmap || kpmap == pv->pv_pmap) {
>             if (entries++ == 0)
>                 npv = pv;
>
>             /* Cacheable mappings */
>             if ((pv->pv_flags & PVF_NC) == 0) {
>                 cacheable_entries++;
>                 if (kpmap == pv->pv_pmap)
>                     kern_cacheable++;
>             }
>
>             /* Writable mappings */
>             if (pv->pv_flags & PVF_WRITE)
>                 ++writable;
>         } else
>         if (pv->pv_flags & PVF_WRITE)
>             other_writable = 1;
>     }
>
>     /*
>      * Enable or disable caching as necessary.
>      * Note: the first entry might be part of the kernel pmap,
>      * so we can't assume this is indicative of the state of the
>      * other (maybe non-kpmap) entries.
>      */
>     if ((entries > 1 && writable) ||
>         (entries > 0 && pm == kpmap && other_writable)) {
>         if (cacheable_entries == 0)
>             return;
This is probably the line that is causing the problem.
>         for (pv = npv; pv; pv = SLIST_NEXT(pv, pv_link)) {
>             if ((pm != pv->pv_pmap && kpmap != pv->pv_pmap) ||
>                 (pv->pv_flags & PVF_NC))
>                 continue;
It appears to me that the warning is valid, since npv may not be set to 
anything.  The header line for the file is

/*    $NetBSD: pmap.c,v 1.183 2008/08/06 19:13:45 matt Exp $    */

Regards,
Don