bug#24320: Error when printing foreign functions

[Robin Templeton <robin@terpri.org>]

The following program causes `(@ (system vm program) print-program)' to
throw an exception when run in Guile 2.1.3.104-8f2f8:

(use-modules (system foreign))
(format #t "~S~%"
 (pointer->procedure double
                     (dynamic-func "sqrt" (dynamic-link))
                     (list double)))

print-program tries to access fields of the procedure's debug info
record even if find-program-debug-info fails and returns #f. The
following patch fixes the problem.

From 0ec7bff9e71f1c1c46fa3c1d2bdbc43f5db3588c Mon Sep 17 00:00:00 2001
From: Robin Templeton <robin@terpri.org>
Date: Sat, 27 Aug 2016 13:42:10 -0400
Subject: [PATCH] Check for missing debug info in print-program

* module/system/vm/program.scm (print-program): Check the return value
  of find-program-debug-info.
---
 module/system/vm/program.scm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/module/system/vm/program.scm b/module/system/vm/program.scm
index 9f5b764..32c96f2 100644
--- a/module/system/vm/program.scm
+++ b/module/system/vm/program.scm
@@ -265,7 +265,7 @@ lists."
          ;; It could be the procedure had its name property set via the
          ;; procedure property interface.
          (name (or (and program (procedure-name program))
-                   (program-debug-info-name pdi)))
+                   (and pdi (program-debug-info-name pdi))))
          (source (match (find-program-sources addr)
                    (() #f)
                    ((source . _) source)))
-- 
2.9.3