Re: Unsecure assoc calls

[Michael Käppler]

Many thanks for all helpful comments.
Attached is the revised patch.

What's the reason that chain-assoc-get is defined separately in 
lily-library.scm:210, though ly_chain_assoc_get exists?

Regards,
Michael

>From 740bd0fcb035099086e9e60a325019fdf25595d4 Mon Sep 17 00:00:00 2001
From: =?utf-8?q?Michael=20K=C3=A4ppler?= <address@hidden>
Date: Sat, 12 Sep 2009 20:36:58 +0200
Subject: [PATCH] Improve error checking in ly:assoc-get and ly:chain-assoc-get.

* Introduce a new optional argument strict_checking

* When strict_checking is set to true, output a programming_error
  if the given key is not found in the given alist / achain.

* This patch does not change the current behaviour. It prepares
  a greater modification to remove all assoc calls through
  secure assoc-get calls.
---
 lily/general-scheme.cc     |   38 +++++++++++++++++++++++++++++---------
 lily/include/lily-guile.hh |    4 ++--
 2 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/lily/general-scheme.cc b/lily/general-scheme.cc
index 43ff745..7372ce6 100644
--- a/lily/general-scheme.cc
+++ b/lily/general-scheme.cc
@@ -154,10 +154,12 @@ LY_DEFINE (ly_dir_p, "ly:dir?",
 }
 
 LY_DEFINE (ly_assoc_get, "ly:assoc-get",
-          2, 1, 0,
-          (SCM key, SCM alist, SCM default_value),
-          "Return value if @var{key} in @var{alist}, else @code{default-value}"
-          " (or @code{#f} if not specified).")
+          2, 2, 0,
+          (SCM key, SCM alist, SCM default_value, SCM strict_checking),
+          "Return value if @var{key} in @var{alist}, else @var{default_value}"
+          " (or @code{#f} if not specified). If @var{strict_checking} is set"
+           " to @code{#t} and @var{key} is not in @var{alist}, a 
programming_error"
+           " is output.")
 {
   LY_ASSERT_TYPE(ly_cheap_is_list, alist, 2);
   
@@ -168,6 +170,14 @@ LY_DEFINE (ly_assoc_get, "ly:assoc-get",
   if (default_value == SCM_UNDEFINED)
     default_value = SCM_BOOL_F;
 
+  if (strict_checking == SCM_BOOL_T)
+    {
+      string key_string = ly_scm2string (scm_object_to_string (key, 
SCM_UNDEFINED));
+      string default_value_string = ly_scm2string (scm_object_to_string 
(default_value, SCM_UNDEFINED)); 
+      programming_error (to_string ("Cannot find key `%s' in alist, setting to 
`%s'.", 
+                         key_string, default_value_string));
+    }
+
   return default_value;
 }
 
@@ -312,10 +322,11 @@ LY_DEFINE (ly_effective_prefix, "ly:effective-prefix",
 }
 
 LY_DEFINE (ly_chain_assoc_get, "ly:chain-assoc-get",
-          2, 1, 0, (SCM key, SCM achain, SCM val),
+          2, 2, 0, (SCM key, SCM achain, SCM default_value, SCM 
strict_checking),
           "Return value for @var{key} from a list of alists @var{achain}."
-          "  If no entry is found, return @var{val} or @code{#f} if"
-          " @var{val} is not specified.")
+          "  If no entry is found, return @var{default_value} or @code{#f} if"
+          " @var{default_value} is not specified. With @var{strict_checking}"
+           " set to @code{#t}, a programming_error is output in such cases.")
 {
   if (scm_is_pair (achain))
     {
@@ -323,9 +334,18 @@ LY_DEFINE (ly_chain_assoc_get, "ly:chain-assoc-get",
       if (scm_is_pair (handle))
        return scm_cdr (handle);
       else
-       return ly_chain_assoc_get (key, scm_cdr (achain), val);
+       return ly_chain_assoc_get (key, scm_cdr (achain), default_value);
     }
-  return val == SCM_UNDEFINED ? SCM_BOOL_F : val;
+  
+  if (strict_checking == SCM_BOOL_T)
+    {
+      string key_string = ly_scm2string (scm_object_to_string (key, 
SCM_UNDEFINED));
+      string default_value_string = ly_scm2string (scm_object_to_string 
(default_value, SCM_UNDEFINED)); 
+      programming_error (to_string ("Cannot find key `%s' in achain, setting 
to `%s'.", 
+                         key_string, default_value_string));
+    }
+
+  return default_value == SCM_UNDEFINED ? SCM_BOOL_F : default_value;
 }
 
 
diff --git a/lily/include/lily-guile.hh b/lily/include/lily-guile.hh
index 88c7fe8..859131a 100644
--- a/lily/include/lily-guile.hh
+++ b/lily/include/lily-guile.hh
@@ -48,9 +48,9 @@ SCM ly_rational2scm (Rational);
 SCM ly_offset2scm (Offset);
 Offset ly_scm2offset (SCM);
 SCM ly_chain_assoc (SCM key, SCM achain);
-SCM ly_chain_assoc_get (SCM key, SCM achain, SCM val);
+SCM ly_chain_assoc_get (SCM key, SCM achain, SCM default_value, SCM 
strict_checking = SCM_BOOL_F);
 SCM ly_assoc_cdr (SCM key, SCM alist);
-SCM ly_assoc_get (SCM key, SCM alist, SCM def);
+SCM ly_assoc_get (SCM key, SCM alist, SCM default_value, SCM strict_checking = 
SCM_BOOL_F);
 Interval ly_scm2interval (SCM);
 Drul_array<Real> ly_scm2realdrul (SCM);
 Slice int_list_to_slice (SCM l);
-- 
1.6.0.2