(directory_file_name): Don't clobber the envvar

when handling top-level rooted dir.

1 files changed, 5 insertions, 3 deletions

diff --git a/src/fileio.c b/src/fileio.c
index e567ed9665e..94261b8218e 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -468,9 +468,11 @@ directory_file_name (src, dst)
                   && (ptr[rlen] == ']' || ptr[rlen] == '>')
                   && ptr[rlen - 1] == '.')
                 {
-                  ptr[rlen - 1] = ']';
-                  ptr[rlen] = '\0';
-                  return directory_file_name (ptr, dst);
+                  char * buf = (char *) alloca (strlen (ptr) + 1);
+                  strcpy (buf, ptr);
+                  buf[rlen - 1] = ']';
+                  buf[rlen] = '\0';
+                  return directory_file_name (buf, dst);
                 }
               else
                 dst[slen - 1] = ':';