bytecomp: Don't inline functions that use byte-switch (Bug#26518)

* lisp/emacs-lisp/bytecomp.el (byte-compile-unfold-bcf): Don't inline
  FORM if the bytecode uses the byte-switch instruction. It is
  impossible to guess the correct stack depth while inlining such
  bytecode, resulting in faulty code.

1 files changed, 46 insertions, 40 deletions

diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
index f0f938da43f..aba07102055 100644
--- a/lisp/emacs-lisp/bytecomp.el
+++ b/lisp/emacs-lisp/bytecomp.el
@@ -3204,47 +3204,53 @@ for symbols generated by the byte compiler itself."
          (fmax2 (if (numberp fargs) (lsh fargs -7)))     ;2*max+rest.
          ;; (fmin (if (numberp fargs) (logand fargs 127)))
          (alen (length (cdr form)))
-         (dynbinds ()))
+         (dynbinds ())
+         lap)
     (fetch-bytecode fun)
-    (mapc 'byte-compile-form (cdr form))
-    (unless fmax2
-      ;; Old-style byte-code.
-      (cl-assert (listp fargs))
-      (while fargs
-        (pcase (car fargs)
-          (`&optional (setq fargs (cdr fargs)))
-          (`&rest (setq fmax2 (+ (* 2 (length dynbinds)) 1))
-                 (push (cadr fargs) dynbinds)
-                 (setq fargs nil))
-          (_ (push (pop fargs) dynbinds))))
-      (unless fmax2 (setq fmax2 (* 2 (length dynbinds)))))
-    (cond
-     ((<= (+ alen alen) fmax2)
-      ;; Add missing &optional (or &rest) arguments.
-      (dotimes (_ (- (/ (1+ fmax2) 2) alen))
-        (byte-compile-push-constant nil)))
-     ((zerop (logand fmax2 1))
-      (byte-compile-report-error
-       (format "Too many arguments for inlined function %S" form))
-      (byte-compile-discard (- alen (/ fmax2 2))))
-     (t
-      ;; Turn &rest args into a list.
-      (let ((n (- alen (/ (1- fmax2) 2))))
-        (cl-assert (> n 0) nil "problem: fmax2=%S alen=%S n=%S" fmax2 alen n)
-        (if (< n 5)
-            (byte-compile-out
-             (aref [byte-list1 byte-list2 byte-list3 byte-list4] (1- n))
-             0)
-          (byte-compile-out 'byte-listN n)))))
-    (mapc #'byte-compile-dynamic-variable-bind dynbinds)
-    (byte-compile-inline-lapcode
-     (byte-decompile-bytecode-1 (aref fun 1) (aref fun 2) t)
-     (1+ start-depth))
-    ;; Unbind dynamic variables.
-    (when dynbinds
-      (byte-compile-out 'byte-unbind (length dynbinds)))
-    (cl-assert (eq byte-compile-depth (1+ start-depth))
-            nil "Wrong depth start=%s end=%s" start-depth byte-compile-depth)))
+    (setq lap (byte-decompile-bytecode-1 (aref fun 1) (aref fun 2) t))
+    ;; optimized switch bytecode makes it impossible to guess the correct
+    ;; `byte-compile-depth', which can result in incorrect inlined code.
+    ;; therefore, we do not inline code that uses the `byte-switch'
+    ;; instruction.
+    (if (assq 'byte-switch lap)
+        (byte-compile-normal-call form)
+      (mapc 'byte-compile-form (cdr form))
+      (unless fmax2
+        ;; Old-style byte-code.
+        (cl-assert (listp fargs))
+        (while fargs
+          (pcase (car fargs)
+            (`&optional (setq fargs (cdr fargs)))
+            (`&rest (setq fmax2 (+ (* 2 (length dynbinds)) 1))
+                    (push (cadr fargs) dynbinds)
+                    (setq fargs nil))
+            (_ (push (pop fargs) dynbinds))))
+        (unless fmax2 (setq fmax2 (* 2 (length dynbinds)))))
+      (cond
+       ((<= (+ alen alen) fmax2)
+        ;; Add missing &optional (or &rest) arguments.
+        (dotimes (_ (- (/ (1+ fmax2) 2) alen))
+          (byte-compile-push-constant nil)))
+       ((zerop (logand fmax2 1))
+        (byte-compile-report-error
+         (format "Too many arguments for inlined function %S" form))
+        (byte-compile-discard (- alen (/ fmax2 2))))
+       (t
+        ;; Turn &rest args into a list.
+        (let ((n (- alen (/ (1- fmax2) 2))))
+          (cl-assert (> n 0) nil "problem: fmax2=%S alen=%S n=%S" fmax2 alen n)
+          (if (< n 5)
+              (byte-compile-out
+               (aref [byte-list1 byte-list2 byte-list3 byte-list4] (1- n))
+               0)
+            (byte-compile-out 'byte-listN n)))))
+      (mapc #'byte-compile-dynamic-variable-bind dynbinds)
+      (byte-compile-inline-lapcode lap (1+ start-depth))
+      ;; Unbind dynamic variables.
+      (when dynbinds
+        (byte-compile-out 'byte-unbind (length dynbinds)))
+      (cl-assert (eq byte-compile-depth (1+ start-depth))
+                 nil "Wrong depth start=%s end=%s" start-depth byte-compile-depth))))
 
 (defun byte-compile-check-variable (var access-type)
   "Do various error checks before a use of the variable VAR."