ptrace compile failure with gcc-8.2 on 32-bit powerpc

[Meelis Roos]

After upgrading my distro compiler to gcc-8.2, Linux fails to compile on 
32-bit powerpc (tested with 4.17, 4.18 and v4.18-7873-gf91e654474d4).


  CC      arch/powerpc/kernel/ptrace.o
In file included from ./include/linux/bitmap.h:9,
                 from ./include/linux/cpumask.h:12,
                 from ./include/linux/rcupdate.h:44,
                 from ./include/linux/rculist.h:11,
                 from ./include/linux/pid.h:5,
                 from ./include/linux/sched.h:14,
                 from arch/powerpc/kernel/ptrace.c:19:
In function ‘memcpy’,
    inlined from ‘user_regset_copyin’ at ./include/linux/regset.h:295:4,
    inlined from ‘vr_set’ at arch/powerpc/kernel/ptrace.c:619:9:
./include/linux/string.h:345:9: error: ‘__builtin_memcpy’ offset [-527, -529] is out of the bounds [0, 16] of object ‘vrsave’ with type ‘union <anonymous>’ [-Werror=array-bounds]
  return __builtin_memcpy(p, q, size);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/powerpc/kernel/ptrace.c: In function ‘vr_set’:
arch/powerpc/kernel/ptrace.c:614:5: note: ‘vrsave’ declared here
   } vrsave;
     ^~~~~~
In file included from ./include/linux/bitmap.h:9,
                 from ./include/linux/cpumask.h:12,
                 from ./include/linux/rcupdate.h:44,
                 from ./include/linux/rculist.h:11,
                 from ./include/linux/pid.h:5,
                 from ./include/linux/sched.h:14,
                 from arch/powerpc/kernel/ptrace.c:19:
In function ‘memcpy’,
    inlined from ‘user_regset_copyout’ at ./include/linux/regset.h:270:4,
    inlined from ‘vr_get’ at arch/powerpc/kernel/ptrace.c:572:9:
./include/linux/string.h:345:9: error: ‘__builtin_memcpy’ offset [-527, -529] is out of the bounds [0, 16] of object ‘vrsave’ with type ‘union <anonymous>’ [-Werror=array-bounds]
  return __builtin_memcpy(p, q, size);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/powerpc/kernel/ptrace.c: In function ‘vr_get’:
arch/powerpc/kernel/ptrace.c:567:5: note: ‘vrsave’ declared here
   } vrsave;
     ^~~~~~
cc1: all warnings being treated as errors
make[1]: *** [scripts/Makefile.build:311: arch/powerpc/kernel/ptrace.o] Error 1


-- 
Meelis Roos (mroos at linux.ee)