Fix bugs related to mutation-sharing substrings

* libguile/strings.c (scm_i_is_narrow_string, scm_i_try_narrow_string,
  scm_i_string_set_x): Check to see if the provided string is a
  mutation-sharing substring, and do the right thing in that case.
  Previously, if such a string was passed to these functions, they would
  behave very badly: while trying to fetch and/or mutate the cell
  containing the stringbuf, they were actually fetching or mutating the
  cell containing the original shared string.  That's because
  mutation-sharing substrings store the original string in CELL_1,
  whereas all other strings store the stringbuf there.

diff --git a/libguile/strings.c b/libguile/strings.c
index 870825a..6e1f9c8 100644 (file)
--- a/libguile/strings.c
+++ b/libguile/strings.c
@@ -436,6 +436,9 @@ scm_i_string_length (SCM str)
 int
 scm_i_is_narrow_string (SCM str)
 {
+  if (IS_SH_STRING (str))
+    str = SH_STRING_STRING (str);
+
   return !STRINGBUF_WIDE (STRING_STRINGBUF (str));
 }
 
@@ -446,6 +449,9 @@ scm_i_is_narrow_string (SCM str)
 int
 scm_i_try_narrow_string (SCM str)
 {
+  if (IS_SH_STRING (str))
+    str = SH_STRING_STRING (str);
+
   SET_STRING_STRINGBUF (str, narrow_stringbuf (STRING_STRINGBUF (str)));
 
   return scm_i_is_narrow_string (str);
@@ -664,6 +670,12 @@ scm_i_string_strcmp (SCM sstr, size_t start_x, const char *cstr)
 void
 scm_i_string_set_x (SCM str, size_t p, scm_t_wchar chr)
 {
+  if (IS_SH_STRING (str))
+    {
+      p += STRING_START (str);
+      str = SH_STRING_STRING (str);
+    }
+
   if (chr > 0xFF && scm_i_is_narrow_string (str))
     SET_STRING_STRINGBUF (str, wide_stringbuf (STRING_STRINGBUF (str)));