signal: use BUILD_BUG() instead of _NSIG_WORDS_is_unsupported_size()

Kill _NSIG_WORDS_is_unsupported_size(), use BUILD_BUG() instead.  This
simplifies the code, avoids the nested-externs warnings, and this way we
do not defer the problem to linker.

Also, fix the indentation in _SIG_SET_BINOP() and _SIG_SET_OP().

Note: this patch assumes that the code like "if (0) BUILD_BUG();" is
valid.  If not (say __compiletime_error() is not defined and thus
__compiletime_error_fallback() uses a negative array) we should fix
BUILD_BUG() and/or BUILD_BUG_ON_MSG().  This code should be fine by
definition, this is the documented purpose of BUILD_BUG().

[sfr@canb.auug.org.au: fix powerpc build failures]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 16 deletions

diff --git a/include/linux/signal.h b/include/linux/signal.h
index 750196fcc0a5..ab1e0392b5ac 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -2,6 +2,7 @@
 #define _LINUX_SIGNAL_H
 
 #include <linux/list.h>
+#include <linux/bug.h>
 #include <uapi/linux/signal.h>
 
 struct task_struct;
@@ -67,7 +68,6 @@ static inline int sigismember(sigset_t *set, int _sig)
 
 static inline int sigisemptyset(sigset_t *set)
 {
-        extern void _NSIG_WORDS_is_unsupported_size(void);
         switch (_NSIG_WORDS) {
         case 4:
                 return (set->sig[3] | set->sig[2] |
@@ -77,7 +77,7 @@ static inline int sigisemptyset(sigset_t *set)
         case 1:
                 return set->sig[0] == 0;
         default:
-                _NSIG_WORDS_is_unsupported_size();
+                BUILD_BUG();
                 return 0;
         }
 }
@@ -90,24 +90,23 @@ static inline int sigisemptyset(sigset_t *set)
 #define _SIG_SET_BINOP(name, op)                                        \
 static inline void name(sigset_t *r, const sigset_t *a, const sigset_t *b) \
 {                                                                       \
-        extern void _NSIG_WORDS_is_unsupported_size(void);              \
         unsigned long a0, a1, a2, a3, b0, b1, b2, b3;                   \
                                                                         \
         switch (_NSIG_WORDS) {                                          \
-            case 4:                                                     \
+        case 4:                                                         \
                 a3 = a->sig[3]; a2 = a->sig[2];                         \
                 b3 = b->sig[3]; b2 = b->sig[2];                         \
                 r->sig[3] = op(a3, b3);                                 \
                 r->sig[2] = op(a2, b2);                                 \
-            case 2:                                                     \
+        case 2:                                                         \
                 a1 = a->sig[1]; b1 = b->sig[1];                         \
                 r->sig[1] = op(a1, b1);                                 \
-            case 1:                                                     \
+        case 1:                                                         \
                 a0 = a->sig[0]; b0 = b->sig[0];                         \
                 r->sig[0] = op(a0, b0);                                 \
                 break;                                                  \
-            default:                                                    \
-                _NSIG_WORDS_is_unsupported_size();                      \
+        default:                                                        \
+                BUILD_BUG();                                            \
         }                                                               \
 }
 
@@ -128,16 +127,14 @@ _SIG_SET_BINOP(sigandnsets, _sig_andn)
 #define _SIG_SET_OP(name, op)                                           \
 static inline void name(sigset_t *set)                                  \
 {                                                                       \
-        extern void _NSIG_WORDS_is_unsupported_size(void);              \
-                                                                        \
         switch (_NSIG_WORDS) {                                          \
-            case 4: set->sig[3] = op(set->sig[3]);                      \
-                    set->sig[2] = op(set->sig[2]);                      \
-            case 2: set->sig[1] = op(set->sig[1]);                      \
-            case 1: set->sig[0] = op(set->sig[0]);                      \
+        case 4: set->sig[3] = op(set->sig[3]);                          \
+                set->sig[2] = op(set->sig[2]);                          \
+        case 2: set->sig[1] = op(set->sig[1]);                          \
+        case 1: set->sig[0] = op(set->sig[0]);                          \
                     break;                                              \
-            default:                                                    \
-                _NSIG_WORDS_is_unsupported_size();                      \
+        default:                                                        \
+                BUILD_BUG();                                            \
         }                                                               \
 }