From c937699735c836a3b990a60d16291e0c900bef5f Mon Sep 17 00:00:00 2001
From: David Benjamin <davidben@google.com>
Date: Mon, 24 Jul 2017 15:31:13 -0400
Subject: [PATCH] Avoid a C++ runtime dependency.

Short-term, we will need to use these macros and build without RTTI when
defining any virtual base class. Long-term, it would be good to remove
these constraints, but it will require some downstream work.

Bug: 132
Change-Id: I3bc65bb12d7653978612b7d1bf06f772a2f3b1cd
Reviewed-on: https://boringssl-review.googlesource.com/18344
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
---
 CMakeLists.txt |  2 +-
 ssl/internal.h | 20 +++++++++++++++++---
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3c2d5562..3f9a3da2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -42,7 +42,7 @@ if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     set(C_CXX_FLAGS "${C_CXX_FLAGS} -Wno-free-nonheap-object")
   endif()
   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${C_CXX_FLAGS} -Wmissing-prototypes -Wold-style-definition -Wstrict-prototypes")
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 ${C_CXX_FLAGS} -Wmissing-declarations -fno-exceptions")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 ${C_CXX_FLAGS} -Wmissing-declarations -fno-exceptions -fno-rtti")
   # In GCC, -Wmissing-declarations is the C++ spelling of -Wmissing-prototypes
   # and using the wrong one is an error. In Clang, -Wmissing-prototypes is the
   # spelling for both and -Wmissing-declarations is some other warning.
diff --git a/ssl/internal.h b/ssl/internal.h
index fb02d35f..5a2e5609 100644
--- a/ssl/internal.h
+++ b/ssl/internal.h
@@ -144,6 +144,8 @@
 
 #include <openssl/base.h>
 
+#include <stdlib.h>
+
 #include <type_traits>
 #include <utility>
 
@@ -217,6 +219,17 @@ UniquePtr<T> MakeUnique(Args &&... args) {
   return UniquePtr<T>(New<T>(std::forward<Args>(args)...));
 }
 
+/* HAS_VIRTUAL_DESTRUCTOR should be declared in any base class which defines a
+ * virtual destructor. This avoids a dependency on |_ZdlPv| and prevents the
+ * class from being used with |delete|. */
+#define HAS_VIRTUAL_DESTRUCTOR \
+  void operator delete(void *) { abort(); }
+
+/* PURE_VIRTUAL should be used instead of = 0 when defining pure-virtual
+ * functions. This avoids a dependency on |__cxa_pure_virtual| but loses
+ * compile-time checking. */
+#define PURE_VIRTUAL { abort(); }
+
 
 /* Protocol versions.
  *
@@ -753,17 +766,18 @@ int custom_ext_add_serverhello(SSL_HANDSHAKE *hs, CBB *extensions);
 class SSLKeyShare {
  public:
   virtual ~SSLKeyShare() {}
+  HAS_VIRTUAL_DESTRUCTOR
 
   /* Create returns a SSLKeyShare instance for use with group |group_id| or
    * nullptr on error. */
   static UniquePtr<SSLKeyShare> Create(uint16_t group_id);
 
   /* GroupID returns the group ID. */
-  virtual uint16_t GroupID() const = 0;
+  virtual uint16_t GroupID() const PURE_VIRTUAL;
 
   /* Offer generates a keypair and writes the public value to
    * |out_public_key|. It returns true on success and false on error. */
-  virtual bool Offer(CBB *out_public_key) = 0;
+  virtual bool Offer(CBB *out_public_key) PURE_VIRTUAL;
 
   /* Accept performs a key exchange against the |peer_key| generated by |offer|.
    * On success, it returns true, writes the public value to |out_public_key|,
@@ -790,7 +804,7 @@ class SSLKeyShare {
    * TODO(davidben): out_secret should be a smart pointer. */
   virtual bool Finish(uint8_t **out_secret, size_t *out_secret_len,
                       uint8_t *out_alert, const uint8_t *peer_key,
-                      size_t peer_key_len) = 0;
+                      size_t peer_key_len) PURE_VIRTUAL;
 };
 
 /* ssl_nid_to_group_id looks up the group corresponding to |nid|. On success, it