Keep a stack reference to bytecode objects being executed (Bug#33014)

* src/eval.c (Ffuncall): Make local variable 'fun' volatile.
* test/src/eval-tests.el
(eval-tests-byte-code-being-evaluated-is-protected-from-gc):
Add regression test for Bug#33014.
(eval-tests-33014-var): New variable.
(eval-tests-33014-func, eval-tests-33014-redefine): New functions.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/eval.c b/src/eval.c
index a51d0c90831..32cfda24d8c 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -2820,8 +2820,11 @@ Thus, (funcall \\='cons \\='x \\='y) returns (x . y).
 usage: (funcall FUNCTION &rest ARGUMENTS)  */)
   (ptrdiff_t nargs, Lisp_Object *args)
 {
-  Lisp_Object fun, original_fun;
-  Lisp_Object funcar;
+  /* Use 'volatile' here to cause optimizing compilers to keep a
+     reference on the stack to the function's bytecode object.  See
+     Bug#33014.  */
+  Lisp_Object volatile fun;
+  Lisp_Object original_fun, funcar;
   ptrdiff_t numargs = nargs - 1;
   Lisp_Object val;
   ptrdiff_t count;