fix(common): better defaults for curl initialization (#9798)

By default, initialize libcurl with locking and signal handlers that
work for most applications. In particular, leaving the default handler
for `SIGPIPE` usually results in the application crashes when a socket
is closed.

Author: coryan

google/cloud/internal/curl_wrappers.cc

@@ -298,9 +298,16 @@ std::string DebugOutData(char const* data, std::size_t size) {
                       " data=", CleanupDebugData(data, size), "\n");
 }
 
+Options CurlInitializeOptions(Options options) {
+  return google::cloud::internal::MergeOptions(
+      std::move(options), Options{}
+                              .set<EnableCurlSigpipeHandlerOption>(true)
+                              .set<EnableCurlSslLockingOption>(true));
+}
+
 void CurlInitializeOnce(Options const& options) {
   static CurlInitializer curl_initializer;
-  static bool const kInitialized = [&options]() {
+  static bool const kInitialized = [](Options const& options) {
     // The Google Cloud Storage C++ client library depends on libcurl, which
     // can use different SSL libraries. Depending on the SSL implementation,
     // we need to take action to be thread-safe. More details can be found here:
@@ -324,7 +331,7 @@ void CurlInitializeOnce(Options const& options) {
     //
     InitializeSigPipeHandler(options.get<EnableCurlSigpipeHandlerOption>());
     return true;
-  }();
+  }(CurlInitializeOptions(options));
   static_cast<void>(kInitialized);
 }
 

google/cloud/internal/curl_wrappers.h

@@ -61,6 +61,9 @@ using CurlShare = std::unique_ptr<CURLSH, decltype(&curl_share_cleanup)>;
 /// Returns true if the SSL locking callbacks are installed.
 bool SslLockingCallbacksInstalled();
 
+/// Return the default global options
+Options CurlInitializeOptions(Options options);
+
 /// Initializes (if needed) the SSL locking callbacks.
 void CurlInitializeOnce(Options const& options);
 

google/cloud/internal/curl_wrappers_test.cc

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include "google/cloud/internal/curl_wrappers.h"
+#include "google/cloud/internal/curl_options.h"
 #include <gmock/gmock.h>
 
 namespace google {
@@ -128,6 +129,22 @@ header2: value2
   }
 }
 
+TEST(CurlWrappers, CurlInitializeOptions) {
+  auto defaults = CurlInitializeOptions({});
+  EXPECT_TRUE(defaults.get<EnableCurlSslLockingOption>());
+  EXPECT_TRUE(defaults.get<EnableCurlSigpipeHandlerOption>());
+
+  auto override1 =
+      CurlInitializeOptions(Options{}.set<EnableCurlSslLockingOption>(false));
+  EXPECT_FALSE(override1.get<EnableCurlSslLockingOption>());
+  EXPECT_TRUE(override1.get<EnableCurlSigpipeHandlerOption>());
+
+  auto override2 = CurlInitializeOptions(
+      Options{}.set<EnableCurlSigpipeHandlerOption>(false));
+  EXPECT_TRUE(override2.get<EnableCurlSslLockingOption>());
+  EXPECT_FALSE(override2.get<EnableCurlSigpipeHandlerOption>());
+}
+
 }  // namespace
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END
 }  // namespace rest_internal