Pacify GCC 9.2.1 20190927 -O3

Original problem report by N. Jackson in:
https://lists.gnu.org/r/emacs-devel/2020-03/msg00047.html
I found some other warnings when I used gcc, and fixed them
with this patch.
* lib-src/etags.c: Include verify.h.
(xnmalloc, xnrealloc): Tell the compiler that NITEMS is
nononnegative and ITEM_SIZE is positive.
* src/conf_post.h (__has_attribute_returns_nonnull)
(ATTRIBUTE_RETURNS_NONNULL): New macros.
* src/editfns.c (Fuser_full_name): Don’t assume Fuser_login_name
returns non-nil.
* src/intervals.c (rotate_right, rotate_left, update_interval):
* src/intervals.h (LENGTH, LEFT_TOTAL_LENGTH, RIGHT_TOTAL_LENGTH):
Use TOTAL_LENGTH0 or equivalent on intervals that might be null.
* src/intervals.h (TOTAL_LENGTH): Assume arg is nonnull.
(TOTAL_LENGTH0): New macro, with the old TOTAL_LENGTH meaning.
(make_interval, split_interval_right): Add ATTRIBUTE_RETURNS_NONNULL.
* src/pdumper.c (dump_check_dump_off): Now returns void, since
no caller uses the return value.  Redo assert to pacify GCC.
(decode_emacs_reloc): Add a seemingly-random eassume to pacify GCC.
Ugly, and I suspect due to a bug in GCC.

1 files changed, 6 insertions, 6 deletions

diff --git a/src/intervals.c b/src/intervals.c
index a66594ceea2..594d8924ebc 100644
--- a/src/intervals.c
+++ b/src/intervals.c
@@ -298,7 +298,7 @@ rotate_right (INTERVAL A)
     set_interval_parent (c, A);
 
   /* A's total length is decreased by the length of B and its left child.  */
-  A->total_length -= B->total_length - TOTAL_LENGTH (c);
+  A->total_length -= TOTAL_LENGTH (B) - TOTAL_LENGTH0 (c);
   eassert (TOTAL_LENGTH (A) > 0);
   eassert (LENGTH (A) > 0);
 
@@ -349,7 +349,7 @@ rotate_left (INTERVAL A)
     set_interval_parent (c, A);
 
   /* A's total length is decreased by the length of B and its right child.  */
-  A->total_length -= B->total_length - TOTAL_LENGTH (c);
+  A->total_length -= TOTAL_LENGTH (B) - TOTAL_LENGTH0 (c);
   eassert (TOTAL_LENGTH (A) > 0);
   eassert (LENGTH (A) > 0);
 
@@ -723,13 +723,13 @@ previous_interval (register INTERVAL interval)
       i->position - LEFT_TOTAL_LENGTH (i)                       \
       - LENGTH (INTERVAL_PARENT (i))
 
-/* Find the interval containing POS, given some non-NULL INTERVAL in
+/* Find the interval containing POS, given some interval I in
    the same tree.  Note that we update interval->position in each
    interval we traverse, assuming it is already correctly set for the
    argument I.  We don't assume that any other interval already has a
    correctly set ->position.  */
 INTERVAL
-update_interval (register INTERVAL i, ptrdiff_t pos)
+update_interval (INTERVAL i, ptrdiff_t pos)
 {
   if (!i)
     return NULL;
@@ -739,7 +739,7 @@ update_interval (register INTERVAL i, ptrdiff_t pos)
       if (pos < i->position)
         {
           /* Move left.  */
-          if (pos >= i->position - TOTAL_LENGTH (i->left))
+          if (pos >= i->position - LEFT_TOTAL_LENGTH (i))
             {
               i->left->position = i->position - TOTAL_LENGTH (i->left)
                 + LEFT_TOTAL_LENGTH (i->left);
@@ -757,7 +757,7 @@ update_interval (register INTERVAL i, ptrdiff_t pos)
       else if (pos >= INTERVAL_LAST_POS (i))
         {
           /* Move right.  */
-          if (pos < INTERVAL_LAST_POS (i) + TOTAL_LENGTH (i->right))
+          if (pos < INTERVAL_LAST_POS (i) + RIGHT_TOTAL_LENGTH (i))
             {
               i->right->position = INTERVAL_LAST_POS (i)
                 + LEFT_TOTAL_LENGTH (i->right);