[librsvg] node.rs: Only drop the RsvgState if *not* in testing mode

[Federico Mena Quintero <federico src gnome org>]

commit d44b0ec3765f7aa5080edfd5f8e3b1296a278fa7
Author: Federico Mena Quintero <federico gnome org>
Date:   Fri Mar 3 14:14:24 2017 -0600

    node.rs: Only drop the RsvgState if *not* in testing mode
    
    We don't have rsvg_state_free() available if we are linking in testing
    mode.  Conditionally compile the Drop trait then; there are no leaks
    because in testing mode we don't create RsvgState objects anyway.
    
    The effect of this commit is to actually free the states in release mode!

 rust/src/node.rs |   16 ++++++++++------
 1 files changed, 10 insertions(+), 6 deletions(-)
---
diff --git a/rust/src/node.rs b/rust/src/node.rs
index b8ed91f..557bc5b 100644
--- a/rust/src/node.rs
+++ b/rust/src/node.rs
@@ -232,13 +232,18 @@ impl Node {
     }
 }
 
-extern "C" {
-    fn rsvg_state_free (state: *mut RsvgState);
-}
-
+// Sigh, rsvg_state_free() is only available if we are being linked into
+// librsvg.so.  In testing mode, we run standalone, so we omit this.
+// Fortunately, in testing mode we don't create "real" nodes with
+// states; we only create stub nodes with ptr::null() for state.
+#[cfg(not(test))]
 impl Drop for Node {
+
     fn drop (&mut self) {
-//        unsafe { rsvg_state_free (self.state); }
+        extern "C" {
+            fn rsvg_state_free (state: *mut RsvgState);
+        }
+        unsafe { rsvg_state_free (self.state); }
     }
 }
 
@@ -389,7 +394,6 @@ mod tests {
     use drawing_ctx::RsvgDrawingCtx;
     use handle::RsvgHandle;
     use property_bag::RsvgPropertyBag;
-    use state::RsvgState;
     use super::*;
     use std::ptr;