fix bug where scm_from_utf8_stringn would not detect bad utf-8

* libguile/strings.c (scm_from_utf8_stringn):
* libguile/symbols.c (utf8_string_equals_wide_string): The "bad UTF8"
  return from u8_mbtouc is a 0xfffd character, not a negative byte
  length.  Fixes a bug in which invalid UTF-8 would not be caught.

* libguile/bytevectors.c (scm_utf8_to_string): Use scm_from_utf8_stringn
  directly.  Just a little cleanup.

* test-suite/tests/iconv.test ("narrow non-ascii string"): Add test for
  parsing bad utf-8 with substitution.

4 files changed, 13 insertions, 8 deletions

diff --git a/libguile/bytevectors.c b/libguile/bytevectors.c
index db132d43f..4ce90ebdf 100644
--- a/libguile/bytevectors.c
+++ b/libguile/bytevectors.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
+/* Copyright (C) 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -2050,8 +2050,7 @@ SCM_DEFINE (scm_utf8_to_string, "utf8->string",
 
   c_utf_len = SCM_BYTEVECTOR_LENGTH (utf);
   c_utf = (char *) SCM_BYTEVECTOR_CONTENTS (utf);
-  str = scm_from_stringn (c_utf, c_utf_len, "UTF-8",
-                          SCM_FAILED_CONVERSION_ERROR);
+  str = scm_from_utf8_stringn (c_utf, c_utf_len);
 
   return (str);
 }
diff --git a/libguile/strings.c b/libguile/strings.c
index 5130cb362..1e89e63d6 100644
--- a/libguile/strings.c
+++ b/libguile/strings.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1995,1996,1998,2000,2001, 2004, 2006, 2008, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
+/* Copyright (C) 1995,1996,1998,2000,2001, 2004, 2006, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -1526,7 +1526,8 @@ scm_from_stringn (const char *str, size_t len, const char *encoding,
 
   if (encoding == NULL || len == 0)
     return scm_from_latin1_stringn (str, len);
-  else if (strcmp (encoding, "UTF-8") == 0)
+  else if (strcmp (encoding, "UTF-8") == 0
+           && handler == SCM_FAILED_CONVERSION_ERROR)
     return scm_from_utf8_stringn (str, len);
 
   u32len = 0;
@@ -1639,7 +1640,7 @@ scm_from_utf8_stringn (const char *str, size_t len)
 
           nbytes = u8_mbtouc (&c, ustr + i, len - i);
 
-          if (nbytes < 0)
+          if (c == 0xfffd)
             /* Bad UTF-8.  */
             decoding_error (__func__, errno, str, len);
 
diff --git a/libguile/symbols.c b/libguile/symbols.c
index fd7e21470..f93833b9d 100644
--- a/libguile/symbols.c
+++ b/libguile/symbols.c
@@ -1,5 +1,5 @@
 /* Copyright (C) 1995, 1996, 1997, 1998, 2000, 2001, 2003, 2004,
- *   2006, 2009, 2011 Free Software Foundation, Inc.
+ *   2006, 2009, 2011, 2013 Free Software Foundation, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -167,7 +167,7 @@ utf8_string_equals_wide_string (const scm_t_uint8 *narrow, size_t nlen,
       nbytes = u8_mbtouc (&c, narrow + byte_idx, nlen - byte_idx);
       if (nbytes == 0)
         break;
-      else if (nbytes < 0)
+      else if (c == 0xfffd)
         /* Bad UTF-8.  */
         return 0;
       else if (c != wide[char_idx])
diff --git a/test-suite/tests/iconv.test b/test-suite/tests/iconv.test
index 9083cd256..be36336f3 100644
--- a/test-suite/tests/iconv.test
+++ b/test-suite/tests/iconv.test
@@ -94,6 +94,11 @@
     (pass-if-exception "misparse latin1 as utf8" exception:decoding-error
       (bytevector->string (string->bytevector s "latin1") "utf-8"))
 
+    (pass-if "misparse latin1 as utf8 with substitutions"
+      (equal? (bytevector->string (string->bytevector s "latin1")
+                                  "utf-8" 'substitute)
+              "?t?"))
+
     (pass-if-exception "misparse latin1 as ascii" exception:decoding-error
       (bytevector->string (string->bytevector s "latin1") "ascii"))))