1 files changed, 94 insertions, 0 deletions
diff --git a/src/dynamic_load_unix.cpp b/src/dynamic_load_unix.cpp
new file mode 100644
index 0000000..17e08fd
--- /dev/null
+++ b/src/dynamic_load_unix.cpp
@@ -0,0 +1,94 @@
+#include <dlfcn.h>
+#include <opentracing/dynamic_load.h>
+#include <opentracing/version.h>
+
+namespace opentracing {
+BEGIN_OPENTRACING_ABI_NAMESPACE
+namespace {
+class DynamicLibraryHandleUnix : public DynamicLibraryHandle {
+ public:
+  explicit DynamicLibraryHandleUnix(void* handle) : handle_{handle} {}
+
+  ~DynamicLibraryHandleUnix() override { dlclose(handle_); }
+
+ private:
+  void* handle_;
+};
+}  // namespace
+
+// Undefined behavior sanitizer has a bug where it will produce a false positive
+// when casting the result of dlsym to a function pointer.
+//
+// See https://github.com/envoyproxy/envoy/pull/2252#issuecomment-362668221
+//     https://github.com/google/sanitizers/issues/911
+//
+// Note: undefined behavior sanitizer is supported in clang and gcc > 4.9
+#if defined(__clang__)
+__attribute__((no_sanitize("function")))
+// Copied from https://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html
+#elif defined(__GNUC__) && \
+    ((__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) >= 40900)
+__attribute__((no_sanitize_undefined))
+#endif
+expected<DynamicTracingLibraryHandle>
+DynamicallyLoadTracingLibrary(const char* shared_library,
+                              std::string& error_message) noexcept try {
+  dlerror();  // Clear any existing error.
+
+  const auto handle = dlopen(shared_library, RTLD_NOW | RTLD_LOCAL);
+  if (handle == nullptr) {
+    error_message = dlerror();
+    return make_unexpected(dynamic_load_failure_error);
+  }
+
+  std::unique_ptr<DynamicLibraryHandle> dynamic_library_handle{
+      new DynamicLibraryHandleUnix{handle}};
+
+  const auto make_tracer_factory =
+      reinterpret_cast<OpenTracingMakeTracerFactoryType**>(
+          dlsym(handle, "OpenTracingMakeTracerFactory"));
+  if (make_tracer_factory == nullptr) {
+    error_message = dlerror();
+    return make_unexpected(dynamic_load_failure_error);
+  }
+
+  if (*make_tracer_factory == nullptr) {
+    error_message =
+        "An error occurred while looking up for OpenTracingMakeTracerFactory. "
+        "It seems that it was set to nullptr.";
+    return make_unexpected(dynamic_load_failure_error);
+  }
+
+  const void* error_category = nullptr;
+  void* tracer_factory = nullptr;
+  const auto rcode = (*make_tracer_factory)(
+      OPENTRACING_VERSION, OPENTRACING_ABI_VERSION, &error_category,
+      static_cast<void*>(&error_message), &tracer_factory);
+  if (rcode != 0) {
+    if (error_category == nullptr) {
+      error_message = "failed to construct a TracerFactory: unknown error code";
+      return make_unexpected(dynamic_load_failure_error);
+    }
+    const auto error_code = std::error_code{
+        rcode, *static_cast<const std::error_category*>(error_category)};
+    if (error_message.empty()) {
+      error_message = error_code.message();
+    }
+    return make_unexpected(dynamic_load_failure_error);
+  }
+
+  if (tracer_factory == nullptr) {
+    error_message =
+        "failed to construct a TracerFactory: `tracer_factory` is null";
+    return make_unexpected(dynamic_load_failure_error);
+  }
+
+  return DynamicTracingLibraryHandle{
+      std::unique_ptr<const TracerFactory>{
+          static_cast<TracerFactory*>(tracer_factory)},
+      std::move(dynamic_library_handle)};
+} catch (const std::bad_alloc&) {
+  return make_unexpected(std::make_error_code(std::errc::not_enough_memory));
+}
+END_OPENTRACING_ABI_NAMESPACE
+}  // namespace opentracing