(Fsubstitute_in_file_name): Always work on a copy.

Calculate total size precisely.  Decode environment variables
before substituting.  (Bug#38)

2 files changed, 39 insertions, 20 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 7389c561f82..dc0fbd183d1 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2009-03-24  Jason Rumney  <jasonr@gnu.org>
+
+        * fileio.c (Fsubstitute_in_file_name): Always work on a copy.
+        Calculate total size precisely.  Decode environment variables
+        before substituting.  (Bug#38)
+
 2009-03-24  Kenichi Handa  <handa@m17n.org>
 
         * font.c (find_font_encoding): Return Qnil for unsupported
diff --git a/src/fileio.c b/src/fileio.c
index ae64be4ba03..4f3573b02d7 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -1629,11 +1629,14 @@ those `/' is discarded.  */)
   unsigned char *target = NULL;
   int total = 0;
   int substituted = 0;
+  int multibyte;
   unsigned char *xnm;
   Lisp_Object handler;
 
   CHECK_STRING (filename);
 
+  multibyte = STRING_MULTIBYTE (filename);
+
   /* If the file name has special constructs in it,
      call the corresponding file handler.  */
   handler = Ffind_file_name_handler (filename, Qsubstitute_in_file_name);
@@ -1641,8 +1644,11 @@ those `/' is discarded.  */)
     return call2 (handler, Qsubstitute_in_file_name, filename);
 
   nm = SDATA (filename);
-#ifdef DOS_NT
+  /* Always work on a copy of the string, in case GC happens during
+     decode of environment variables, causing the original Lisp_String
+     data to be relocated.  */
   nm = strcpy (alloca (strlen (nm) + 1), nm);
+#ifdef DOS_NT
   CORRECT_DIR_SEPS (nm);
   substituted = (strcmp (nm, SDATA (filename)) != 0);
 #endif
@@ -1655,9 +1661,7 @@ those `/' is discarded.  */)
        again.  Important with filenames like "/home/foo//:/hello///there"
        which whould substitute to "/:/hello///there" rather than "/there".  */
     return Fsubstitute_in_file_name
-      (make_specified_string (p, -1, endp - p,
-                              STRING_MULTIBYTE (filename)));
-
+      (make_specified_string (p, -1, endp - p, multibyte));
 
   /* See if any variables are substituted into the string
      and find the total length of their values in `total' */
@@ -1703,8 +1707,16 @@ those `/' is discarded.  */)
         /* Get variable value */
         o = (unsigned char *) egetenv (target);
         if (o)
-          { /* Eight-bit chars occupy upto 2 bytes in multibyte.  */
-            total += strlen (o) * (STRING_MULTIBYTE (filename) ? 2 : 1);
+          {
+            /* Don't try to guess a maximum length - UTF8 can use up to
+               four bytes per character.  This code is unlikely to run
+               in a situation that requires performance, so decoding the
+               env variables twice should be acceptable. Note that
+               decoding may cause a garbage collect.  */
+            Lisp_Object orig, decoded;
+            orig = make_unibyte_string (o, strlen (o));
+            decoded = DECODE_FILE (orig);
+            total += SBYTES (decoded);
             substituted = 1;
           }
         else if (*p == '}')
@@ -1762,21 +1774,22 @@ those `/' is discarded.  */)
             *x++ = '$';
             strcpy (x, target); x+= strlen (target);
           }
-        else if (STRING_MULTIBYTE (filename))
-          {
-            /* If the original string is multibyte,
-               convert what we substitute into multibyte.  */
-            while (*o)
-              {
-                int c = *o++;
-                c = unibyte_char_to_multibyte (c);
-                x += CHAR_STRING (c, x);
-              }
-          }
         else
           {
-            strcpy (x, o);
-            x += strlen (o);
+            Lisp_Object orig, decoded;
+            int orig_length, decoded_length;
+            orig_length = strlen (o);
+            orig = make_unibyte_string (o, orig_length);
+            decoded = DECODE_FILE (orig);
+            decoded_length = SBYTES (decoded);
+            strncpy (x, SDATA (decoded), decoded_length);
+            x += decoded_length;
+
+            /* If environment variable needed decoding, return value
+               needs to be multibyte.  */
+            if (decoded_length != orig_length
+                || strncmp (SDATA (decoded), o, orig_length))
+              multibyte = 1;
           }
       }
 
@@ -1789,7 +1802,7 @@ those `/' is discarded.  */)
        need to quote some $ to $$ first.  */
     xnm = p;
 
-  return make_specified_string (xnm, -1, x - xnm, STRING_MULTIBYTE (filename));
+  return make_specified_string (xnm, -1, x - xnm, multibyte);
 
  badsubst:
   error ("Bad format environment-variable substitution");