src: Rewrite defer function template

src/asio_http2_handler.cc

@@ -525,7 +525,7 @@ int http2_handler::start() {
     return -1;
   }
 
-  auto cb_del = util::defer(callbacks, nghttp2_session_callbacks_del);
+  auto cb_del = defer(nghttp2_session_callbacks_del, callbacks);
 
   nghttp2_session_callbacks_set_on_begin_headers_callback(
       callbacks, on_begin_headers_callback);
@@ -548,7 +548,7 @@ int http2_handler::start() {
     return -1;
   }
 
-  auto opt_del = util::defer(option, nghttp2_option_del);
+  auto opt_del = defer(nghttp2_option_del, option);
 
   nghttp2_option_set_recv_client_preface(option, 1);
 

src/asio_http2_impl.cc

@@ -135,10 +135,10 @@ void http2_impl::backlog(int backlog) { backlog_ = backlog; }
 
 } // namespace server
 
-template <typename T, typename F>
-std::shared_ptr<util::Defer<T, F>> defer_shared(T &&t, F f) {
-  return std::make_shared<util::Defer<T, F>>(std::forward<T>(t),
-                                             std::forward<F>(f));
+template <typename F, typename... T>
+std::shared_ptr<Defer<F, T...>> defer_shared(F &&f, T &&... t) {
+  return std::make_shared<Defer<F, T...>>(std::forward<F>(f),
+                                          std::forward<T>(t)...);
 }
 
 read_cb file_reader(const std::string &path) {
@@ -151,7 +151,7 @@ read_cb file_reader(const std::string &path) {
 }
 
 read_cb file_reader_from_fd(int fd) {
-  auto d = defer_shared(static_cast<int>(fd), close);
+  auto d = defer_shared(close, fd);
 
   return [fd, d](uint8_t *buf, size_t len) -> read_cb::result_type {
     int rv;

src/h2load.cc

@@ -280,7 +280,7 @@ void print_server_tmp_key(SSL *ssl) {
     return;
   }
 
-  auto key_del = util::defer(key, EVP_PKEY_free);
+  auto key_del = defer(EVP_PKEY_free, key);
 
   std::cout << "Server Temp Key: ";
 
@@ -293,7 +293,7 @@ void print_server_tmp_key(SSL *ssl) {
     break;
   case EVP_PKEY_EC: {
     auto ec = EVP_PKEY_get1_EC_KEY(key);
-    auto ec_del = util::defer(ec, EC_KEY_free);
+    auto ec_del = defer(EC_KEY_free, ec);
     auto nid = EC_GROUP_get_curve_name(EC_KEY_get0_group(ec));
     auto cname = EC_curve_nid2nist(nid);
     if (!cname) {

src/h2load_http2_session.cc

@@ -28,6 +28,7 @@
 
 #include "h2load.h"
 #include "util.h"
+#include "template.h"
 
 using namespace nghttp2;
 
@@ -126,8 +127,7 @@ void Http2Session::on_connect() {
 
   nghttp2_session_callbacks_new(&callbacks);
 
-  auto callbacks_deleter =
-      util::defer(callbacks, nghttp2_session_callbacks_del);
+  auto callbacks_deleter = defer(nghttp2_session_callbacks_del, callbacks);
 
   nghttp2_session_callbacks_set_on_frame_recv_callback(callbacks,
                                                        on_frame_recv_callback);

src/nghttp.cc

@@ -2136,7 +2136,7 @@ int run(char **uris, int n) {
   nghttp2_session_callbacks *callbacks;
 
   nghttp2_session_callbacks_new(&callbacks);
-  auto cbsdel = util::defer(callbacks, nghttp2_session_callbacks_del);
+  auto cbsdel = defer(nghttp2_session_callbacks_del, callbacks);
 
   nghttp2_session_callbacks_set_on_stream_close_callback(
       callbacks, on_stream_close_callback);

src/shrpx_http2_session.cc

@@ -1174,8 +1174,7 @@ int Http2Session::on_connect() {
     return -1;
   }
 
-  auto callbacks_deleter =
-      util::defer(callbacks, nghttp2_session_callbacks_del);
+  auto callbacks_deleter = defer(nghttp2_session_callbacks_del, callbacks);
 
   nghttp2_session_callbacks_set_on_stream_close_callback(
       callbacks, on_stream_close_callback);

src/shrpx_http2_upstream.cc

@@ -666,8 +666,7 @@ Http2Upstream::Http2Upstream(ClientHandler *handler)
 
   assert(rv == 0);
 
-  auto callbacks_deleter =
-      util::defer(callbacks, nghttp2_session_callbacks_del);
+  auto callbacks_deleter = defer(nghttp2_session_callbacks_del, callbacks);
 
   nghttp2_session_callbacks_set_on_stream_close_callback(
       callbacks, on_stream_close_callback);

src/shrpx_ssl.cc

@@ -639,7 +639,7 @@ void get_altnames(X509 *cert, std::vector<std::string> &dns_names,
   GENERAL_NAMES *altnames = static_cast<GENERAL_NAMES *>(
       X509_get_ext_d2i(cert, NID_subject_alt_name, nullptr, nullptr));
   if (altnames) {
-    auto altnames_deleter = util::defer(altnames, GENERAL_NAMES_free);
+    auto altnames_deleter = defer(GENERAL_NAMES_free, altnames);
     size_t n = sk_GENERAL_NAME_num(altnames);
     for (size_t i = 0; i < n; ++i) {
       const GENERAL_NAME *altname = sk_GENERAL_NAME_value(altnames, i);
@@ -699,7 +699,7 @@ int check_cert(SSL *ssl) {
     LOG(ERROR) << "No certificate found";
     return -1;
   }
-  auto cert_deleter = util::defer(cert, X509_free);
+  auto cert_deleter = defer(X509_free, cert);
   long verify_res = SSL_get_verify_result(ssl);
   if (verify_res != X509_V_OK) {
     LOG(ERROR) << "Certificate verification failed: "
@@ -877,7 +877,7 @@ int cert_lookup_tree_add_cert_from_file(CertLookupTree *lt, SSL_CTX *ssl_ctx,
     LOG(ERROR) << "BIO_new failed";
     return -1;
   }
-  auto bio_deleter = util::defer(bio, BIO_vfree);
+  auto bio_deleter = defer(BIO_vfree, bio);
   if (!BIO_read_filename(bio, certfile)) {
     LOG(ERROR) << "Could not read certificate file '" << certfile << "'";
     return -1;
@@ -888,7 +888,7 @@ int cert_lookup_tree_add_cert_from_file(CertLookupTree *lt, SSL_CTX *ssl_ctx,
                << "'";
     return -1;
   }
-  auto cert_deleter = util::defer(cert, X509_free);
+  auto cert_deleter = defer(X509_free, cert);
   std::string common_name;
   std::vector<std::string> dns_names;
   std::vector<std::string> ip_addrs;

src/template.h

@@ -54,6 +54,23 @@ template <typename T, size_t N> constexpr size_t array_size(T (&)[N]) {
   return N;
 }
 
+// inspired by <http://blog.korfuri.fr/post/go-defer-in-cpp/>, but our
+// template can take functions returning other than void.
+template <typename F, typename... T> struct Defer {
+  Defer(F &&f, T &&... t)
+      : f(std::bind(std::forward<F>(f), std::forward<T>(t)...)) {}
+  Defer(Defer &&o) : f(std::move(o.f)) {}
+  ~Defer() { f(); }
+
+  using ResultType = typename std::result_of<
+      typename std::decay<F>::type(typename std::decay<T>::type...)>::type;
+  std::function<ResultType()> f;
+};
+
+template <typename F, typename... T> Defer<F, T...> defer(F &&f, T &&... t) {
+  return Defer<F, T...>(std::forward<F>(f), std::forward<T>(t)...);
+}
+
 } // namespace nghttp2
 
 #endif // TEMPLATE_H

src/util.h

@@ -54,19 +54,6 @@ namespace nghttp2 {
 
 namespace util {
 
-template <typename T, typename F> struct Defer {
-  Defer(T t, F f) : t(t), f(std::move(f)) {}
-
-  ~Defer() { f(t); }
-
-  T t;
-  F f;
-};
-
-template <typename T, typename F> Defer<T, F> defer(T &&t, F f) {
-  return Defer<T, F>(std::forward<T>(t), std::forward<F>(f));
-}
-
 extern const char DEFAULT_STRIP_CHARSET[];
 
 template <typename InputIterator>