vm_call_symbol: check stack overflow

VM stack could overflow here.  The condition is when a symbol is passed
to a block-taking method via &variable, and that symbol has never been
used for actual method names (thus yielding that results in calling
method_missing), and the VM stack is full (no single word left).  This
is a once-in-a-blue-moon event.  Yet there is a very tiny room of stack
overflow.  We need to check that.

1 files changed, 1 insertions, 0 deletions

diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index e36ce10237..bd6b0a2c01 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -2708,6 +2708,7 @@ vm_call_symbol(
          * --+------+--------+------+------
          */
         int i = argc;
+        CHECK_VM_STACK_OVERFLOW(reg_cfp, 1);
         INC_SP(1);
         MEMMOVE(&TOPN(i - 1), &TOPN(i), VALUE, i);
         argc = ++calling->argc;