Avoid crashes when casifying noncontiguous regions

This is a followon fix for Bug#37477.
* lisp/simple.el (region-extract-function):
Use setq here, since the var is now defined in C code.
* src/casefiddle.c (casify_pnc_region): New function.
(Fupcase_region, Fdowncase_region, Fcapitalize_region)
(Fupcase_initials_region): Use it.
(Fupcase_initials_region): Add region-noncontiguous-p flag
for consistency with the others.  All uses changed.
(syms_of_casefiddle): Define Qbounds, Vregion_extract_function.
* src/insdel.c (prepare_to_modify_buffer_1):
* src/keyboard.c (command_loop_1):
Use Vregion_extraction_function.
* src/insdel.c (syms_of_insdel): No need to define
Qregion_extract_function.
* test/src/casefiddle-tests.el (casefiddle-oldfunc): New var.
(casefiddle-loopfunc, casefiddle-badfunc): New functions.
(casefiddle-invalid-region-extract-function): New test.

7 files changed, 73 insertions, 75 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 8a880e5b63a..73f0ca2497b 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -488,7 +488,8 @@ interface that's more like functions like 'search-forward'.
 ---
 ** More commands support noncontiguous rectangular regions, namely
 'upcase-dwim', 'downcase-dwim', 'capitalize-dwim', 'capitalize-region',
-'replace-string', 'replace-regexp', and 'delimit-columns-region'.
+'upcase-initials-region', 'replace-string', 'replace-regexp', and
+'delimit-columns-region'.
 
 +++
 ** When asked to visit a large file, Emacs now offers visiting it literally.
diff --git a/lisp/simple.el b/lisp/simple.el
index 31e3b2bbaba..ecd7eb797e8 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -1087,7 +1087,7 @@ instead of deleted."
   :group 'killing
   :version "24.1")
 
-(defvar region-extract-function
+(setq region-extract-function
   (lambda (method)
     (when (region-beginning)
       (cond
@@ -1096,19 +1096,7 @@ instead of deleted."
        ((eq method 'delete-only)
         (delete-region (region-beginning) (region-end)))
        (t
-        (filter-buffer-substring (region-beginning) (region-end) method)))))
-  "Function to get the region's content.
-Called with one argument METHOD which can be:
-- nil: return the content as a string (list of strings for
-  non-contiguous regions).
-- `delete-only': delete the region; the return value is undefined.
-- `bounds': return the boundaries of the region as a list of one
-  or more cons cells of the form (START . END).
-- anything else: delete the region and return its content
-  as a string (or list of strings for non-contiguous regions),
-  after filtering it with `filter-buffer-substring', which
-  is called, for each contiguous sub-region, with METHOD as its
-  3rd argument.")
+        (filter-buffer-substring (region-beginning) (region-end) method))))))
 
 (defvar region-insert-function
   (lambda (lines)
diff --git a/src/casefiddle.c b/src/casefiddle.c
index 3a1724b306d..774906df04d 100644
--- a/src/casefiddle.c
+++ b/src/casefiddle.c
@@ -516,34 +516,43 @@ casify_region (enum case_action flag, Lisp_Object b, Lisp_Object e)
   return orig_end + added;
 }
 
-DEFUN ("upcase-region", Fupcase_region, Supcase_region, 2, 3,
-       "(list (region-beginning) (region-end) (region-noncontiguous-p))",
-       doc: /* Convert the region to upper case.  In programs, wants two arguments.
-These arguments specify the starting and ending character numbers of
-the region to operate on.  When used as a command, the text between
-point and the mark is operated on.
-See also `capitalize-region'.  */)
-  (Lisp_Object beg, Lisp_Object end, Lisp_Object region_noncontiguous_p)
-{
-  Lisp_Object bounds = Qnil;
+/* Casify a possibly noncontiguous region according to FLAG.  BEG and
+   END specify the bounds, except that if REGION_NONCONTIGUOUS_P is
+   non-nil, the region's bounds are specified by (funcall
+   region-extract-function 'bounds) instead.  */
 
+static Lisp_Object
+casify_pnc_region (enum case_action flag, Lisp_Object beg, Lisp_Object end,
+		   Lisp_Object region_noncontiguous_p)
+{
   if (!NILP (region_noncontiguous_p))
     {
-      bounds = call1 (Fsymbol_value (Qregion_extract_function),
-		      intern ("bounds"));
-
-      while (CONSP (bounds))
+      Lisp_Object bounds = call1 (Vregion_extract_function, Qbounds);
+      FOR_EACH_TAIL (bounds)
 	{
-	  casify_region (CASE_UP, XCAR (XCAR (bounds)), XCDR (XCAR (bounds)));
-	  bounds = XCDR (bounds);
+	  CHECK_CONS (XCAR (bounds));
+	  casify_region (flag, XCAR (XCAR (bounds)), XCDR (XCAR (bounds)));
 	}
+      CHECK_LIST_END (bounds, bounds);
     }
   else
-    casify_region (CASE_UP, beg, end);
+    casify_region (flag, beg, end);
 
   return Qnil;
 }
 
+DEFUN ("upcase-region", Fupcase_region, Supcase_region, 2, 3,
+       "(list (region-beginning) (region-end) (region-noncontiguous-p))",
+       doc: /* Convert the region to upper case.  In programs, wants two arguments.
+These arguments specify the starting and ending character numbers of
+the region to operate on.  When used as a command, the text between
+point and the mark is operated on.
+See also `capitalize-region'.  */)
+  (Lisp_Object beg, Lisp_Object end, Lisp_Object region_noncontiguous_p)
+{
+  return casify_pnc_region (CASE_UP, beg, end, region_noncontiguous_p);
+}
+
 DEFUN ("downcase-region", Fdowncase_region, Sdowncase_region, 2, 3,
        "(list (region-beginning) (region-end) (region-noncontiguous-p))",
        doc: /* Convert the region to lower case.  In programs, wants two arguments.
@@ -552,23 +561,7 @@ the region to operate on.  When used as a command, the text between
 point and the mark is operated on.  */)
   (Lisp_Object beg, Lisp_Object end, Lisp_Object region_noncontiguous_p)
 {
-  Lisp_Object bounds = Qnil;
-
-  if (!NILP (region_noncontiguous_p))
-    {
-      bounds = call1 (Fsymbol_value (Qregion_extract_function),
-		      intern ("bounds"));
-
-      while (CONSP (bounds))
-	{
-	  casify_region (CASE_DOWN, XCAR (XCAR (bounds)), XCDR (XCAR (bounds)));
-	  bounds = XCDR (bounds);
-	}
-    }
-  else
-    casify_region (CASE_DOWN, beg, end);
-
-  return Qnil;
+  return casify_pnc_region (CASE_DOWN, beg, end, region_noncontiguous_p);
 }
 
 DEFUN ("capitalize-region", Fcapitalize_region, Scapitalize_region, 2, 3,
@@ -580,38 +573,23 @@ In programs, give two arguments, the starting and ending
 character positions to operate on.  */)
   (Lisp_Object beg, Lisp_Object end, Lisp_Object region_noncontiguous_p)
 {
-  Lisp_Object bounds = Qnil;
-
-  if (!NILP (region_noncontiguous_p))
-    {
-      bounds = call1 (Fsymbol_value (Qregion_extract_function),
-		      intern ("bounds"));
-
-      while (CONSP (bounds))
-	{
-	  casify_region (CASE_CAPITALIZE, XCAR (XCAR (bounds)), XCDR (XCAR (bounds)));
-	  bounds = XCDR (bounds);
-	}
-    }
-  else
-    casify_region (CASE_CAPITALIZE, beg, end);
-
-  return Qnil;
+  return casify_pnc_region (CASE_CAPITALIZE, beg, end, region_noncontiguous_p);
 }
 
 /* Like Fcapitalize_region but change only the initials.  */
 
 DEFUN ("upcase-initials-region", Fupcase_initials_region,
-       Supcase_initials_region, 2, 2, "r",
+       Supcase_initials_region, 2, 3,
+       "(list (region-beginning) (region-end) (region-noncontiguous-p))",
        doc: /* Upcase the initial of each word in the region.
 This means that each word's first character is converted to either
 title case or upper case, and the rest are left unchanged.
 In programs, give two arguments, the starting and ending
 character positions to operate on.  */)
-  (Lisp_Object beg, Lisp_Object end)
+     (Lisp_Object beg, Lisp_Object end, Lisp_Object region_noncontiguous_p)
 {
-  casify_region (CASE_CAPITALIZE_UP, beg, end);
-  return Qnil;
+  return casify_pnc_region (CASE_CAPITALIZE_UP, beg, end,
+			    region_noncontiguous_p);
 }
 
 static Lisp_Object
@@ -668,12 +646,28 @@ With negative argument, capitalize previous words but do not move.  */)
 void
 syms_of_casefiddle (void)
 {
+  DEFSYM (Qbounds, "bounds");
   DEFSYM (Qidentity, "identity");
   DEFSYM (Qtitlecase, "titlecase");
   DEFSYM (Qspecial_uppercase, "special-uppercase");
   DEFSYM (Qspecial_lowercase, "special-lowercase");
   DEFSYM (Qspecial_titlecase, "special-titlecase");
 
+  DEFVAR_LISP ("region-extract-function", Vregion_extract_function,
+	       doc: /* Function to get the region's content.
+Called with one argument METHOD which can be:
+- nil: return the content as a string (list of strings for
+  non-contiguous regions).
+- `delete-only': delete the region; the return value is undefined.
+- `bounds': return the boundaries of the region as a list of one
+  or more cons cells of the form (START . END).
+- anything else: delete the region and return its content
+  as a string (or list of strings for non-contiguous regions),
+  after filtering it with `filter-buffer-substring', which
+  is called, for each contiguous sub-region, with METHOD as its
+  3rd argument.  */);
+  Vregion_extract_function = Qnil; /* simple.el sets this.  */
+
   defsubr (&Supcase);
   defsubr (&Sdowncase);
   defsubr (&Scapitalize);
diff --git a/src/insdel.c b/src/insdel.c
index 093b841d6d6..ebfd022ac6b 100644
--- a/src/insdel.c
+++ b/src/insdel.c
@@ -2002,7 +2002,7 @@ prepare_to_modify_buffer_1 (ptrdiff_t start, ptrdiff_t end,
 	  : (!NILP (Vselect_active_regions)
 	     && !NILP (Vtransient_mark_mode))))
     Vsaved_region_selection
-      = call1 (Fsymbol_value (Qregion_extract_function), Qnil);
+      = call1 (Vregion_extract_function, Qnil);
 
   signal_before_change (start, end, preserve_ptr);
   Fset (Qdeactivate_mark, Qt);
@@ -2401,7 +2401,5 @@ handling of the active region per `select-active-regions'.  */);
   inhibit_modification_hooks = 0;
   DEFSYM (Qinhibit_modification_hooks, "inhibit-modification-hooks");
 
-  DEFSYM (Qregion_extract_function, "region-extract-function");
-
   defsubr (&Scombine_after_change_execute);
 }
diff --git a/src/keyboard.c b/src/keyboard.c
index 1b9a603ca17..a16d13cc7b8 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -1535,7 +1535,7 @@ command_loop_1 (void)
 				  Vselection_inhibit_update_commands)))
 		{
 		  Lisp_Object txt
-		    = call1 (Fsymbol_value (Qregion_extract_function), Qnil);
+		    = call1 (Vregion_extract_function, Qnil);
 		  if (XFIXNUM (Flength (txt)) > 0)
 		    /* Don't set empty selections.  */
 		    call2 (Qgui_set_selection, QPRIMARY, txt);
diff --git a/src/search.c b/src/search.c
index 9b674a58102..1e57d2ecbe5 100644
--- a/src/search.c
+++ b/src/search.c
@@ -2739,7 +2739,7 @@ since only regular expressions have distinguished subexpressions.  */)
 		    Qnil);
   else if (case_action == cap_initial)
     Fupcase_initials_region (make_fixnum (search_regs.start[sub]),
-			     make_fixnum (newpoint));
+			     make_fixnum (newpoint), Qnil);
 
   /* The replace_range etc. functions can trigger modification hooks
      (see signal_before_change and signal_after_change).  Try to error
diff --git a/test/src/casefiddle-tests.el b/test/src/casefiddle-tests.el
index ed9a2f93306..54793f2cda4 100644
--- a/test/src/casefiddle-tests.el
+++ b/test/src/casefiddle-tests.el
@@ -259,5 +259,22 @@
       (should (eq tc (capitalize ch)))
       (should (eq tc (upcase-initials ch))))))
 
+(defvar casefiddle-oldfunc region-extract-function)
+
+(defun casefiddle-loopfunc (method)
+  (if (eq method 'bounds)
+      (let ((looping (list '(1 . 1))))
+        (setcdr looping looping))
+    (funcall casefiddle-oldfunc method)))
+
+(defun casefiddle-badfunc (method)
+  (if (eq method 'bounds)
+      '(())
+    (funcall casefiddle-oldfunc method)))
+
+(ert-deftest casefiddle-invalid-region-extract-function ()
+  (dolist (region-extract-function '(casefiddle-badfunc casefiddle-loopfunc))
+    (with-temp-buffer
+      (should-error (upcase-region nil nil t)))))
 
 ;;; casefiddle-tests.el ends here