http: make strings independent before modification

Ruby strings may be copy-on-write (multiple #dup'ed strings can
point to the same internal buffers).  So since
HttpParser#headers modifies its buffer argument, we'll need to
make sure the String object we have points to its own private
buffer.

This doesn't affect Unicorn except in a to-be-written test case
that relies on a #dup'ed String.

1 files changed, 2 insertions, 0 deletions

diff --git a/ext/unicorn_http/unicorn_http.rl b/ext/unicorn_http/unicorn_http.rl
index 19091f4..ed9c359 100644
--- a/ext/unicorn_http/unicorn_http.rl
+++ b/ext/unicorn_http/unicorn_http.rl
@@ -383,6 +383,8 @@ static void advance_str(VALUE str, off_t nr)
   if (len == 0)
     return;
 
+  rb_str_modify(str);
+
   assert(nr <= len);
   len -= nr;
   if (len > 0) /* unlikely, len is usually 0 */