More robust error handling

- Check if socket is alive before waiting to write to it to prevent SIGPIPE
- Consume SIGPIPE on client
- Read response line and headers after bad request

Author: chansikpark

httplib.h

@@ -7133,7 +7133,7 @@ inline ssize_t SocketStream::read(char *ptr, size_t size) {
 }
 
 inline ssize_t SocketStream::write(const char *ptr, size_t size) {
-  if (!wait_writable()) { return -1; }
+  if (!detail::is_socket_alive(sock_) || !wait_writable()) { return -1; }
 
 #if defined(_WIN32) && !defined(_WIN64)
   size =
@@ -8618,7 +8618,11 @@ inline ClientImpl::ClientImpl(const std::string &host, int port,
                               const std::string &client_key_path)
     : host_(detail::escape_abstract_namespace_unix_domain(host)), port_(port),
       host_and_port_(detail::make_host_and_port_string(host_, port, is_ssl())),
-      client_cert_path_(client_cert_path), client_key_path_(client_key_path) {}
+      client_cert_path_(client_cert_path), client_key_path_(client_key_path) {
+#ifndef _WIN32
+  signal(SIGPIPE, SIG_IGN);
+#endif
+}
 
 inline ClientImpl::~ClientImpl() {
   // Wait until all the requests in flight are handled.
@@ -9516,7 +9520,7 @@ inline bool ClientImpl::process_request(Stream &strm, Request &req,
                                         Response &res, bool close_connection,
                                         Error &error) {
   // Send request
-  if (!write_request(strm, req, close_connection, error)) { return false; }
+  bool wrote = write_request(strm, req, close_connection, error);
 
 #ifdef CPPHTTPLIB_OPENSSL_SUPPORT
   if (is_ssl()) {
@@ -9539,6 +9543,8 @@ inline bool ClientImpl::process_request(Stream &strm, Request &req,
     return false;
   }
 
+  if (!wrote) return false;
+
   // Body
   if ((res.status != StatusCode::NoContent_204) && req.method != "HEAD" &&
       req.method != "CONNECT") {

test/test.cc

@@ -5898,6 +5898,48 @@ TEST_F(ServerTest, BadRequestLineCancelsKeepAlive) {
   EXPECT_FALSE(cli_.is_socket_open());
 }
 
+TEST_F(ServerTest, SendLargeBodyAfterRequestLineError) {
+  Request post;
+  post.method = "POST";
+  post.path = "/post-large?q=" + LONG_QUERY_VALUE;
+  post.body = LARGE_DATA;
+
+  auto start = std::chrono::high_resolution_clock::now();
+
+  auto resPost = std::make_shared<Response>();
+  auto error = Error::Success;
+  cli_.set_keep_alive(true);
+  auto ret = cli_.send(post, *resPost, error);
+
+  auto end = std::chrono::high_resolution_clock::now();
+  auto elapsed =
+      std::chrono::duration_cast<std::chrono::milliseconds>(end - start)
+          .count();
+
+  EXPECT_FALSE(ret);
+  EXPECT_EQ(StatusCode::UriTooLong_414, resPost->status);
+  EXPECT_EQ("close", resPost->get_header_value("Connection"));
+  EXPECT_FALSE(cli_.is_socket_open());
+  EXPECT_LE(elapsed, 200);
+
+  // Send an extra GET request to ensure error recovery without hanging
+  Request get;
+  get.method = "GET";
+  get.path = "/hi";
+
+  start = std::chrono::high_resolution_clock::now();
+  auto resGet = cli_.send(get);
+  end = std::chrono::high_resolution_clock::now();
+  elapsed =
+      std::chrono::duration_cast<std::chrono::milliseconds>(end - start)
+          .count();
+
+  ASSERT_TRUE(resGet);
+  EXPECT_EQ(StatusCode::OK_200, resGet->status);
+  EXPECT_EQ("Hello World!", resGet->body);
+  EXPECT_LE(elapsed, 100);
+}
+
 TEST_F(ServerTest, StartTime) { auto res = cli_.Get("/test-start-time"); }
 
 #ifdef CPPHTTPLIB_ZLIB_SUPPORT