Pacify GCC 12 in default developer build

This lets ‘./configure; make’ work on Fedora 36 x86-64 from a Git
checkout without generating false-alarm warnings.
* lib-src/etags.c (main): There appeared to be false alarm with
GCC 12.  However, the code was wrong anyway, as it mishandled file
names containing "'" so fix that bug.  This pacifies GCC.
(mercury_decl): Omit tests ‘s + pos != NULL’ that were apparently
intended to be ‘s[pos] != '\0'’ but which were miscoded to always
be true and which were mostly not needed anyway.  In one place,
though, a test was needed, so fix that by using strchr instead.
* src/alloc.c (lisp_free) [!GC_MALLOC_CHECK]:
* src/term.c (Fsuspend_tty): Don’t look at a pointer after freeing
it, even just to test it for equality with some other pointer, as
this has undefined behavior in C and GCC 12 diagnoses this.
* src/dbusbind.c (xd_read_message_1): Rework the code a bit
so that it has fewer tests.  This pacifies GCC 12 which was
complaining incorrectly about dereferencing a null pointer.
* src/intervals.c (copy_properties): Remove an eassume that should
no longer be needed even to pacify older GCCs, due to ...
* src/intervals.h (split_interval_left): ... this addition of
ATTRIBUTE_RETURNS_NONNULL to pacify a GCC 12 warning about
dereferencing a null pointer.
* src/regex-emacs.c (EXTEND_BUFFER): Use negative values rather
than auxiliary booleans to indicate null pointers.  This pacifies
GCC 12 false alarms about using uninitialized variables.
* src/xdisp.c (clear_position): New function.
(append_space_for_newline, extend_face_to_end_of_line):
Use it to work around false alarms from GCC 12.
(display_and_set_cursor): Add an UNINIT to pacify GCC 12.
* src/xterm.c (x_draw_glyphless_glyph_string_foreground):
Defend against hypothetical bad code elsewhere;
this also pacifies GCC 12.
(x_term_init): Use fixed-size auto array rather than alloca,
as the array is small; this also pacifies GCC 12.

8 files changed, 59 insertions, 49 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 43fbbb79bed..3cfc3d61ddd 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -1032,9 +1032,12 @@ lisp_free (void *block)
     return;
 
   MALLOC_BLOCK_INPUT;
+#ifndef GC_MALLOC_CHECK
+  struct mem_node *m = mem_find (block);
+#endif
   free (block);
 #ifndef GC_MALLOC_CHECK
-  mem_delete (mem_find (block));
+  mem_delete (m);
 #endif
   MALLOC_UNBLOCK_INPUT;
 }
diff --git a/src/dbusbind.c b/src/dbusbind.c
index 7cfdbbe23cf..943a4aff8e7 100644
--- a/src/dbusbind.c
+++ b/src/dbusbind.c
@@ -1690,29 +1690,30 @@ xd_read_message_1 (DBusConnection *connection, Lisp_Object bus)
       value = Fgethash (key, Vdbus_registered_objects_table, Qnil);
 
       /* Loop over the registered functions.  Construct an event.  */
-      while (!NILP (value))
+      for (; !NILP (value); value = CDR_SAFE (value))
         {
           key = CAR_SAFE (value);
+          Lisp_Object key_uname = CAR_SAFE (key);
           /* key has the structure (UNAME SERVICE PATH HANDLER).  */
-          if (((uname == NULL)
-               || (NILP (CAR_SAFE (key)))
-               || (strcmp (uname, SSDATA (CAR_SAFE (key))) == 0))
-              && ((path == NULL)
-                  || (NILP (CAR_SAFE (CDR_SAFE (CDR_SAFE (key)))))
-                  || (strcmp (path,
-                              SSDATA (CAR_SAFE (CDR_SAFE (CDR_SAFE (key)))))
-                      == 0))
-              && (!NILP (CAR_SAFE (CDR_SAFE (CDR_SAFE (CDR_SAFE (key)))))))
-            {
-              EVENT_INIT (event);
-              event.kind = DBUS_EVENT;
-              event.frame_or_window = Qnil;
-              /* Handler.  */
-              event.arg
-                = Fcons (CAR_SAFE (CDR_SAFE (CDR_SAFE (CDR_SAFE (key)))), args);
-              break;
-            }
-          value = CDR_SAFE (value);
+          if (uname && !NILP (key_uname)
+              && strcmp (uname, SSDATA (key_uname)) != 0)
+            continue;
+          Lisp_Object key_service_etc = CDR_SAFE (key);
+          Lisp_Object key_path_etc = CDR_SAFE (key_service_etc);
+          Lisp_Object key_path = CAR_SAFE (key_path_etc);
+          if (path && !NILP (key_path)
+              && strcmp (path, SSDATA (key_path)) != 0)
+            continue;
+          Lisp_Object handler = CAR_SAFE (CDR_SAFE (key_path_etc));
+          if (NILP (handler))
+            continue;
+
+          /* Construct an event and exit the loop.  */
+          EVENT_INIT (event);
+          event.kind = DBUS_EVENT;
+          event.frame_or_window = Qnil;
+          event.arg = Fcons (handler, args);
+          break;
         }
 
       if (NILP (value))
diff --git a/src/intervals.c b/src/intervals.c
index 687b237b9ea..9e28637d6bc 100644
--- a/src/intervals.c
+++ b/src/intervals.c
@@ -121,7 +121,6 @@ copy_properties (INTERVAL source, INTERVAL target)
 {
   if (DEFAULT_INTERVAL_P (source) && DEFAULT_INTERVAL_P (target))
     return;
-  eassume (source && target);
 
   COPY_INTERVAL_CACHE (source, target);
   set_interval_plist (target, Fcopy_sequence (source->plist));
diff --git a/src/intervals.h b/src/intervals.h
index 484fca2e756..0ce581208e3 100644
--- a/src/intervals.h
+++ b/src/intervals.h
@@ -251,7 +251,7 @@ extern void traverse_intervals_noorder (INTERVAL,
                                         void (*) (INTERVAL, void *), void *);
 extern INTERVAL split_interval_right (INTERVAL, ptrdiff_t)
   ATTRIBUTE_RETURNS_NONNULL;
-extern INTERVAL split_interval_left (INTERVAL, ptrdiff_t);
+extern INTERVAL split_interval_left (INTERVAL, ptrdiff_t) ATTRIBUTE_RETURNS_NONNULL;
 extern INTERVAL find_interval (INTERVAL, ptrdiff_t);
 extern INTERVAL next_interval (INTERVAL);
 extern INTERVAL previous_interval (INTERVAL);
diff --git a/src/regex-emacs.c b/src/regex-emacs.c
index 700a6c357de..8662fe8d6d0 100644
--- a/src/regex-emacs.c
+++ b/src/regex-emacs.c
@@ -1244,21 +1244,22 @@ static int analyze_first (re_char *p, re_char *pend,
       return REG_ESIZE;                                                 \
     ptrdiff_t b_off = b - old_buffer;                                   \
     ptrdiff_t begalt_off = begalt - old_buffer;                         \
-    bool fixup_alt_jump_set = !!fixup_alt_jump;                         \
-    bool laststart_set = !!laststart;                                   \
-    bool pending_exact_set = !!pending_exact;                           \
-    ptrdiff_t fixup_alt_jump_off, laststart_off, pending_exact_off;     \
-    if (fixup_alt_jump_set) fixup_alt_jump_off = fixup_alt_jump - old_buffer; \
-    if (laststart_set) laststart_off = laststart - old_buffer;          \
-    if (pending_exact_set) pending_exact_off = pending_exact - old_buffer; \
+    ptrdiff_t fixup_alt_jump_off =                                      \
+      fixup_alt_jump ? fixup_alt_jump - old_buffer : -1;                \
+    ptrdiff_t laststart_off = laststart ? laststart - old_buffer : -1;  \
+    ptrdiff_t pending_exact_off =                                       \
+      pending_exact ? pending_exact - old_buffer : -1;                  \
     bufp->buffer = xpalloc (bufp->buffer, &bufp->allocated,             \
                             requested_extension, MAX_BUF_SIZE, 1);      \
     unsigned char *new_buffer = bufp->buffer;                           \
     b = new_buffer + b_off;                                             \
     begalt = new_buffer + begalt_off;                                   \
-    if (fixup_alt_jump_set) fixup_alt_jump = new_buffer + fixup_alt_jump_off; \
-    if (laststart_set) laststart = new_buffer + laststart_off;          \
-    if (pending_exact_set) pending_exact = new_buffer + pending_exact_off; \
+    if (0 <= fixup_alt_jump_off)                                        \
+      fixup_alt_jump = new_buffer + fixup_alt_jump_off;                 \
+    if (0 <= laststart_off)                                             \
+      laststart = new_buffer + laststart_off;                           \
+    if (0 <= pending_exact_off)                                         \
+      pending_exact = new_buffer + pending_exact_off;                   \
   } while (false)
 
 
diff --git a/src/term.c b/src/term.c
index bad1127c93b..3bea621dbda 100644
--- a/src/term.c
+++ b/src/term.c
@@ -2287,9 +2287,9 @@ A suspended tty may be resumed by calling `resume-tty' on it.  */)
       delete_keyboard_wait_descriptor (fileno (f));
 
 #ifndef MSDOS
-      fclose (f);
       if (f != t->display_info.tty->output)
         fclose (t->display_info.tty->output);
+      fclose (f);
 #endif
 
       t->display_info.tty->input = 0;
diff --git a/src/xdisp.c b/src/xdisp.c
index 82a018485d3..5ff54b2884f 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -22471,6 +22471,13 @@ compute_line_metrics (struct it *it)
 }
 
 
+static void
+clear_position (struct it *it)
+{
+  it->position.charpos = 0;
+  it->position.bytepos = 0;
+}
+
 /* Append one space to the glyph row of iterator IT if doing a
    window-based redisplay.  The space has the same face as
    IT->face_id.  Value is true if a space was added.
@@ -22506,7 +22513,7 @@ append_space_for_newline (struct it *it, bool default_face_p)
       struct face *face;
 
       it->what = IT_CHARACTER;
-      memset (&it->position, 0, sizeof it->position);
+      clear_position (it);
       it->object = Qnil;
       it->len = 1;
 
@@ -22835,7 +22842,7 @@ extend_face_to_end_of_line (struct it *it)
               const int stretch_width =
                 indicator_column - it->current_x - char_width;
 
-              memset (&it->position, 0, sizeof it->position);
+              clear_position (it);
 
               /* Only generate a stretch glyph if there is distance
                  between current_x and the indicator position.  */
@@ -22869,7 +22876,7 @@ extend_face_to_end_of_line (struct it *it)
 
               if (stretch_width > 0)
                 {
-                  memset (&it->position, 0, sizeof it->position);
+                  clear_position (it);
                   append_stretch_glyph (it, Qnil, stretch_width,
                                         it->ascent + it->descent,
                                         stretch_ascent);
@@ -22919,7 +22926,7 @@ extend_face_to_end_of_line (struct it *it)
                 (((it->ascent + it->descent)
                   * FONT_BASE (font)) / FONT_HEIGHT (font));
               saved_pos = it->position;
-              memset (&it->position, 0, sizeof it->position);
+              clear_position (it);
               saved_avoid_cursor = it->avoid_cursor_p;
               it->avoid_cursor_p = true;
               saved_face_id = it->face_id;
@@ -22957,7 +22964,7 @@ extend_face_to_end_of_line (struct it *it)
       enum display_element_type saved_what = it->what;
 
       it->what = IT_CHARACTER;
-      memset (&it->position, 0, sizeof it->position);
+      clear_position (it);
       it->object = Qnil;
       it->c = it->char_to_display = ' ';
       it->len = 1;
@@ -32651,7 +32658,7 @@ display_and_set_cursor (struct window *w, bool on,
 {
   struct frame *f = XFRAME (w->frame);
   int new_cursor_type;
-  int new_cursor_width;
+  int new_cursor_width UNINIT;
   bool active_cursor;
   struct glyph_row *glyph_row;
   struct glyph *glyph;
diff --git a/src/xterm.c b/src/xterm.c
index 5c5de191dcc..165b0a6b01e 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -6621,6 +6621,10 @@ x_draw_glyphless_glyph_string_foreground (struct glyph_string *s)
                         glyph->ascent + glyph->descent - 1);
       x += glyph->pixel_width;
    }
+
+  /* Defend against hypothetical bad code elsewhere that uses
+     s->char2b after this function returns.  */
+  s->char2b = NULL;
 }
 
 #ifdef USE_X_TOOLKIT
@@ -23521,7 +23525,8 @@ x_term_init (Lisp_Object display_name, char *xrm_option, char *resource_name)
 #ifdef USE_XCB
   xcb_connection_t *xcb_conn;
 #endif
-  char *cm_atom_sprintf;
+  static char const cm_atom_fmt[] = "_NET_WM_CM_S%d";
+  char cm_atom_sprintf[sizeof cm_atom_fmt - 2 + INT_STRLEN_BOUND (int)];
 
   block_input ();
 
@@ -24212,14 +24217,8 @@ x_term_init (Lisp_Object display_name, char *xrm_option, char *resource_name)
       dpyinfo->resx = (mm < 1) ? 100 : pixels * 25.4 / mm;
     }
 
-  {
-    int n = snprintf (NULL, 0, "_NET_WM_CM_S%d",
-                      XScreenNumberOfScreen (dpyinfo->screen));
-    cm_atom_sprintf = alloca (n + 1);
-
-    snprintf (cm_atom_sprintf, n + 1, "_NET_WM_CM_S%d",
-              XScreenNumberOfScreen (dpyinfo->screen));
-  }
+  sprintf (cm_atom_sprintf, cm_atom_fmt,
+           XScreenNumberOfScreen (dpyinfo->screen));
 
   {
     static const struct