Allow custom deleters to opt out of self reset checks for scoped_ptr.

The self-reset check makes sense for the default deleters, because it
would otherwise leave a dangling pointer stored in the scoped_ptr.
However, a custom deleter might actually decrement a reference count
under the hood. This self-reset check can make assignment operators
implementation a lot uglier. One example is net's KeyPair: because
there might be a self-assignment, the original code needed to proxy
the incoming scoped_ptrs via a stack temporary before moving them
into their final location.

BUG=418347

Review URL: https://codereview.chromium.org/610533003

Cr-Commit-Position: refs/heads/master@{#299571}

2 files changed, 3 insertions, 0 deletions

diff --git a/crypto/scoped_nss_types.h b/crypto/scoped_nss_types.h
index 8e96e8d..fdfb83c 100644
--- a/crypto/scoped_nss_types.h
+++ b/crypto/scoped_nss_types.h
@@ -16,6 +16,7 @@ namespace crypto {
 
 template <typename Type, void (*Destroyer)(Type*)>
 struct NSSDestroyer {
+  typedef void AllowSelfReset;
   void operator()(Type* ptr) const {
     Destroyer(ptr);
   }
@@ -23,6 +24,7 @@ struct NSSDestroyer {
 
 template <typename Type, void (*Destroyer)(Type*, PRBool), PRBool freeit>
 struct NSSDestroyer1 {
+  typedef void AllowSelfReset;
   void operator()(Type* ptr) const {
     Destroyer(ptr, freeit);
   }
diff --git a/crypto/scoped_openssl_types.h b/crypto/scoped_openssl_types.h
index d0428fb..cc056e4 100644
--- a/crypto/scoped_openssl_types.h
+++ b/crypto/scoped_openssl_types.h
@@ -22,6 +22,7 @@ namespace crypto {
 // base::internal::RunnableAdapter<>, but that's far too heavy weight.
 template <typename Type, void (*Destroyer)(Type*)>
 struct OpenSSLDestroyer {
+  typedef void AllowSelfReset;
   void operator()(Type* ptr) const { Destroyer(ptr); }
 };