warning cleanup: suspicious switch fallthrough cases.

This is the seventh round of an effort to enable GCC's -Wextra
option. Warnings about switch fallthrough situations are
addressed. GCC now has a diagnostic for this that is enabled
by -Wextra in such a way that if a fallthrough comment is
present, the diagnostic is suppressed. In much of the code,
we have such a comment. It's missing in a few places, or
misplaced. There are also some real bugs.

* hash.c (hash_buf): Add fallthrough comments to intentional
fallthrough cases.
(hash_hash_op): bugfix: add break statement. The 32 and 64
bit cases are independent (at compile time).

* lib.c (cdr, nullify, list_collect, empty): Add fallthrough
comment.
(int_str): Add missing break. This has not caused a
bug though because setting the octzero flag in the zerox
case is harmless to the logic which follows.

* linenoise.c (edit): Move misplaced fallthrough.

* sysif.c (fcntl_wrap): Bugfix: add missing break, without
which errno is tampered to hold EINVAL, in spite of a
successful F_SETLK, F_SETLKW or F_GETLK operation.

* unwind.h (jmp_restore): Declare noreturn, so that GCC
does not issue a false positive warning about a fallthrough
in uw_unwind_to_exit_point.

* utf8.c (utf8_from_buf, utf8_decode): Move a fallthrough
comment outside of preprocessing, so it is properly processed
by GCC's diagnostic.

1 files changed, 5 insertions, 0 deletions

diff --git a/hash.c b/hash.c
index 9f4df00b..8a298de2 100644
--- a/hash.c
+++ b/hash.c
@@ -155,10 +155,13 @@ static u32_t hash_buf(const mem_t *ptr, ucnum size, u32_t seed, int *pcount)
     switch (size) {
     case 3:
       in |= convert(u32_t, tail[2]) << 16;
+      /* fallthrough */
     case 2:
       in |= convert(u32_t, tail[1]) << 8;
+      /* fallthrough */
     case 1:
       in |= convert(u32_t, tail[0]);
+      break;
     }
 
     acc ^= in;
@@ -472,8 +475,10 @@ static ucnum hash_hash_op(val obj, int *count, ucnum seed)
   switch (CHAR_BIT * sizeof (mem_t *)) {
   case 32:
     out += coerce(ucnum, h->hops) >> 4;
+    break;
   case 64: default:
     out += coerce(ucnum, h->hops) >> 5;
+    break;
   }
 
   out += equal_hash(h->userdata, count, seed);