Fix trivial -Wundef warnings

* See [Feature #17752]

Co-authored-by: xtkoba (Tee KOBAYASHI) <xtkoba+ruby@gmail.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/vm_exec.c b/vm_exec.c
index 7aa56f6ad6..305ff90261 100644
--- a/vm_exec.c
+++ b/vm_exec.c
@@ -104,6 +104,8 @@ vm_exec_core(rb_execution_context_t *ec, VALUE initial)
 #else
     register rb_control_frame_t *reg_cfp;
     const VALUE *reg_pc;
+#define USE_MACHINE_REGS 0
+
 #endif
 
 #if USE_MACHINE_REGS