Fix the subr-arity returned by native compiled functions with lots of args

This fixes bug #58739.  Make subr-arity return, e.g., (12 . 12) rather than
(12 . many) for a function with a fixed number of arguments more than 8.

* lisp/emacs-lisp/comp.el (comp-prepare-args-for-top-level): Only return a cdr
of 'many when there are &rest arguments.

* src/eval.c (eval_sub): Also check for a fixed number of args over 8 when
using the nargs + *args calling convention.
(funcall_subr): Also check numargs <= 8 before using the fixed args calling
convention.  Include the case numargs > 8 in the aMany calling convention.

* src/lisp.h (DEFUN): Amend the comment about MANY.

3 files changed, 17 insertions, 14 deletions

diff --git a/lisp/emacs-lisp/comp.el b/lisp/emacs-lisp/comp.el
index 3987692f6f9..21395c23d9a 100644
--- a/lisp/emacs-lisp/comp.el
+++ b/lisp/emacs-lisp/comp.el
@@ -2057,9 +2057,10 @@ and the annotation emission."
   "Lexically-scoped FUNCTION."
   (let ((args (comp-func-l-args function)))
     (cons (make-comp-mvar :constant (comp-args-base-min args))
-          (make-comp-mvar :constant (if (comp-args-p args)
-                                        (comp-args-max args)
-                                      'many)))))
+          (make-comp-mvar :constant (cond
+                                     ((comp-args-p args) (comp-args-max args))
+                                     ((comp-nargs-rest args) 'many)
+                                     (t (comp-nargs-nonrest args)))))))
 
 (cl-defmethod comp-prepare-args-for-top-level ((function comp-func-d))
   "Dynamically scoped FUNCTION."
diff --git a/src/eval.c b/src/eval.c
index e1399d6a05c..ea238299488 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -2435,7 +2435,9 @@ eval_sub (Lisp_Object form)
 
       else if (XSUBR (fun)->max_args == UNEVALLED)
         val = (XSUBR (fun)->function.aUNEVALLED) (args_left);
-      else if (XSUBR (fun)->max_args == MANY)
+      else if (XSUBR (fun)->max_args == MANY
+               || XSUBR (fun)->max_args > 8)
+
         {
           /* Pass a vector of evaluated arguments.  */
           Lisp_Object *vals;
@@ -2998,7 +3000,8 @@ funcall_subr (struct Lisp_Subr *subr, ptrdiff_t numargs, Lisp_Object *args)
   if (numargs >= subr->min_args)
     {
       /* Conforming call to finite-arity subr.  */
-      if (numargs <= subr->max_args)
+      if (numargs <= subr->max_args
+          && subr->max_args <= 8)
         {
           Lisp_Object argbuf[8];
           Lisp_Object *a;
@@ -3034,15 +3037,13 @@ funcall_subr (struct Lisp_Subr *subr, ptrdiff_t numargs, Lisp_Object *args)
               return subr->function.a8 (a[0], a[1], a[2], a[3], a[4], a[5],
                                         a[6], a[7]);
             default:
-              /* If a subr takes more than 8 arguments without using MANY
-                 or UNEVALLED, we need to extend this function to support it.
-                 Until this is done, there is no way to call the function.  */
-              emacs_abort ();
+              emacs_abort ();   /* Can't happen. */
             }
         }
 
       /* Call to n-adic subr.  */
-      if (subr->max_args == MANY)
+      if (subr->max_args == MANY
+          || subr->max_args > 8)
         return subr->function.aMANY (numargs, args);
     }
 
diff --git a/src/lisp.h b/src/lisp.h
index 4701dfa868d..d87f9549382 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -3183,10 +3183,11 @@ CHECK_SUBR (Lisp_Object x)
  `minargs' should be a number, the minimum number of arguments allowed.
  `maxargs' should be a number, the maximum number of arguments allowed,
     or else MANY or UNEVALLED.
-    MANY means pass a vector of evaluated arguments,
-         in the form of an integer number-of-arguments
-         followed by the address of a vector of Lisp_Objects
-         which contains the argument values.
+    MANY means there are &rest arguments.  Here we pass a vector
+        of evaluated arguments in the form of an integer
+        number-of-arguments followed by the address of a vector of
+        Lisp_Objects which contains the argument values.  (We also use
+        this convention when calling a subr with more than 8 parameters.)
     UNEVALLED means pass the list of unevaluated arguments
  `intspec' says how interactive arguments are to be fetched.
     If the string starts with a `(', `intspec' is evaluated and the resulting