10082.diff

commit 2dde6c803a9e50c5bff74095187b0cb2e12eebdd
Author: Behdad Esfahbod <behdad@behdad.org>
Date:   Tue Aug 28 11:02:00 2018 -0700

    Explicitly pass reference in hb_auto_t constructor
    
    Fixes clang bots as well as fuzzer issue.

diff --git a/src/hb-dsalgs.hh b/src/hb-dsalgs.hh
index ec5708eb7..8c910748b 100644
--- a/src/hb-dsalgs.hh
+++ b/src/hb-dsalgs.hh
@@ -492,9 +492,16 @@ template <typename Type>
 struct hb_auto_t : Type
 {
   hb_auto_t (void) { Type::init (); }
-  template <typename T1> hb_auto_t (T1 t1) { Type::init (t1); }
+  /* Explicitly allow the following only for pointer and references,
+   * to avoid any accidental copies.
+   *
+   * Apparently if we template for all types, then gcc seems to
+   * capture a reference argument in the type, but clang doesn't,
+   * causing unwanted copies and bugs that come with it. */
+  template <typename T1> hb_auto_t (T1 *t1) { Type::init (t1); }
+  template <typename T1> hb_auto_t (T1 &t1) { Type::init (t1); }
   ~hb_auto_t (void) { Type::fini (); }
   private: /* Hide */
   void init (void) {}
   void fini (void) {}
 };