From 08d7492cf0eab3165ca260b8aa060de8ae508e1c Mon Sep 17 00:00:00 2001
From: Andy Wingo <wingo@pobox.com>
Date: Thu, 10 Dec 2009 16:03:23 +0100
Subject: [PATCH] add gbt macro to gdbinit, and fix a bug in program-arity

* gdbinit: Add gbt macro, to make a Guile backtrace whenever you want.
* module/system/vm/program.scm (program-arity): If ip is #f, just take
  the first arity.
---
 gdbinit                      | 4 ++++
 module/system/vm/program.scm | 1 +
 2 files changed, 5 insertions(+)

diff --git a/gdbinit b/gdbinit
index 812f04b59..fdc9c759b 100644
--- a/gdbinit
+++ b/gdbinit
@@ -198,3 +198,7 @@ end
 define inst
   p scm_instruction_table[$arg0]
 end
+
+define gbt
+  call scm_display_backtrace (scm_make_stack(0x404,0x304), scm_current_error_port (), 0x704, 0x704, 0x704)
+end
diff --git a/module/system/vm/program.scm b/module/system/vm/program.scm
index 99f9a3cb9..31b667bb0 100644
--- a/module/system/vm/program.scm
+++ b/module/system/vm/program.scm
@@ -121,6 +121,7 @@
     (and arities
          (let lp ((arities arities))
            (cond ((null? arities) #f)
+                 ((not ip) (car arities)) ; take the first one
                  ((and (< (arity:start (car arities)) ip)
                        (<= ip (arity:end (car arities))))
                   (car arities))