make SvOOK_offset macro safer, with parens and underscores

diff --git a/sv.h b/sv.h
index c841c3e..882ba92 100644 (file)
--- a/sv.h
+++ b/sv.h
@@ -2074,23 +2074,23 @@ Evaluates I<sv> more than once.  Sets I<len> to 0 if C<SvOOK(sv)> is false.
 #  define SvOOK_offset(sv, offset) STMT_START {                                \
        assert(sizeof(offset) == sizeof(STRLEN));                       \
        if (SvOOK(sv)) {                                                \
-           const U8 *crash = (U8*)SvPVX_const(sv);                     \
-           offset = *--crash;                                          \
-           if (!offset) {                                              \
-               crash -= sizeof(STRLEN);                                \
-               Copy(crash, (U8 *)&offset, sizeof(STRLEN), U8);         \
+           const U8 *_crash = (U8*)SvPVX_const(sv);                    \
+           (offset) = *--_crash;                                       \
+           if (!(offset)) {                                            \
+               _crash -= sizeof(STRLEN);                               \
+               Copy(_crash, (U8 *)&(offset), sizeof(STRLEN), U8);      \
            }                                                           \
            {                                                           \
                /* Validate the preceding buffer's sentinels to         \
                   verify that no-one is using it.  */                  \
-               const U8 *const bonk = (U8 *) SvPVX_const(sv) - offset; \
-               while (crash > bonk) {                                  \
-                   --crash;                                            \
-                   assert (*crash == (U8)PTR2UV(crash));               \
+               const U8 *const _bonk = (U8*)SvPVX_const(sv) - (offset);\
+               while (_crash > _bonk) {                                \
+                   --_crash;                                           \
+                   assert (*_crash == (U8)PTR2UV(_crash));             \
                }                                                       \
            }                                                           \
        } else {                                                        \
-           offset = 0;                                                 \
+           (offset) = 0;                                               \
        }                                                               \
     } STMT_END
 #else
@@ -2098,13 +2098,13 @@ Evaluates I<sv> more than once.  Sets I<len> to 0 if C<SvOOK(sv)> is false.
 #  define SvOOK_offset(sv, offset) STMT_START {                                \
        assert(sizeof(offset) == sizeof(STRLEN));                       \
        if (SvOOK(sv)) {                                                \
-           offset = ((U8*)SvPVX_const(sv))[-1];                        \
-           if (!offset) {                                              \
+           (offset) = ((U8*)SvPVX_const(sv))[-1];                      \
+           if (!(offset)) {                                            \
                Copy(SvPVX_const(sv) - 1 - sizeof(STRLEN),              \
-                    (U8 *)&offset, sizeof(STRLEN), U8);                \
+                    (U8*)&(offset), sizeof(STRLEN), U8);               \
            }                                                           \
        } else {                                                        \
-           offset = 0;                                                 \
+           (offset) = 0;                                               \
        }                                                               \
     } STMT_END
 #endif