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.

1 files changed, 19 insertions, 14 deletions

diff --git a/lib-src/etags.c b/lib-src/etags.c
index 65b9fae8d5a..ea99ed9f396 100644
--- a/lib-src/etags.c
+++ b/lib-src/etags.c
@@ -1427,14 +1427,19 @@ main (int argc, char **argv)
   if (CTAGS)
     if (append_to_tagfile || update)
       {
-        char *cmd = xmalloc (2 * strlen (tagfile) + sizeof "sort -u -o..");
         /* Maybe these should be used:
            setenv ("LC_COLLATE", "C", 1);
            setenv ("LC_ALL", "C", 1); */
-        char *z = stpcpy (cmd, "sort -u -o ");
-        z = stpcpy (z, tagfile);
-        *z++ = ' ';
-        strcpy (z, tagfile);
+        char *cmd = xmalloc (8 * strlen (tagfile) + sizeof "sort -u -o '' ''");
+        char *z = stpcpy (cmd, "sort -u -o '");
+        char *escaped_tagfile = z;
+        for (; *tagfile; *z++ = *tagfile++)
+          if (*tagfile == '\'')
+            z = stpcpy (z, "'\\'");
+        ptrdiff_t escaped_tagfile_len = z - escaped_tagfile;
+        z = stpcpy (z, "' '");
+        z = mempcpy (z, escaped_tagfile, escaped_tagfile_len);
+        strcpy (z, "'");
         return system (cmd);
       }
   return EXIT_SUCCESS;
@@ -6396,7 +6401,8 @@ mercury_decl (char *s, size_t pos)
   size_t origpos;
   origpos = pos;
 
-  while (s + pos != NULL && (c_isalnum (s[pos]) || s[pos] == '_')) ++pos;
+  while (c_isalnum (s[pos]) || s[pos] == '_')
+    pos++;
 
   unsigned char decl_type_length = pos - origpos;
   char buf[decl_type_length + 1];
@@ -6440,9 +6446,9 @@ mercury_decl (char *s, size_t pos)
                so this is the hard case.  */
             if (strcmp (buf, "solver") == 0)
               {
-                ++pos;
-                while (s + pos != NULL && (c_isalnum (s[pos]) || s[pos] == '_'))
-                  ++pos;
+                do
+                  pos++;
+                while (c_isalnum (s[pos]) || s[pos] == '_');
 
                 decl_type_length = pos - origpos;
                 char buf2[decl_type_length + 1];
@@ -6492,7 +6498,6 @@ mercury_decl (char *s, size_t pos)
       while (c_isalnum (s[pos])
              || s[pos] == '_'
              || (s[pos] == '.' /* A module dot.  */
-                 && s + pos + 1 != NULL
                  && (c_isalnum (s[pos + 1]) || s[pos + 1] == '_')
                  && (module_dot_pos = pos)))  /* Record module dot position.
                                                  Erase module from name.  */
@@ -6536,10 +6541,10 @@ mercury_decl (char *s, size_t pos)
     }
   else if (is_mercury_quantifier && s[pos] == '[')   /* :- some [T] pred/func.  */
     {
-      for (++pos; s + pos != NULL && s[pos] != ']'; ++pos) {}
-      if (s + pos == NULL) return null_pos;
-      ++pos;
-      pos = skip_spaces (s + pos) - s;
+      char *close_bracket = strchr (s + pos + 1, ']');
+      if (!close_bracket)
+        return null_pos;
+      pos = skip_spaces (close_bracket + 1) - s;
       mercury_pos_t position = mercury_decl (s, pos);
       position.totlength += pos - origpos;
       return position;