build dd-trace-cpp as a submodule within nginx-datadog (#24)

* create multiple build target types, one of which (*-objects) nginx-datadog will consume

* Tracer::config_json()

* include "tags" in to_json(rule)

* forbid assignment to Span

* factor out parsing of propagation styles

* use libstdc++ for fuzzing, even with clang

Author: dgoffredo

CMakeLists.txt

@@ -19,8 +19,13 @@ set(CMAKE_CXX_EXTENSIONS OFF)
 
 # If we're building with clang, then use the libc++ version of the standard
 # library instead of libstdc++. Better coverage of build configurations.
-if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
+#
+# But there's one exception: libfuzzer is built with libstdc++ on Ubuntu,
+# and so won't link to libc++. So, if any of the FUZZ_* variables are set,
+# keep to libstdc++ (the default on most systems).
+if ((CMAKE_CXX_COMPILER_ID STREQUAL "Clang") AND (NOT ${FUZZ_W3C_PROPAGATION}))
+    add_compile_options(-stdlib=libc++)
+    add_link_options(-stdlib=libc++)
 endif()
 
 include(ProcessorCount)
@@ -74,8 +79,8 @@ if(BUILD_COVERAGE)
   set(COVERAGE_LIBRARIES gcov)
 endif()
 
-add_library(dd_trace_cpp SHARED)
-target_sources(dd_trace_cpp PRIVATE
+add_library(dd_trace_cpp-objects OBJECT)
+target_sources(dd_trace_cpp-objects PRIVATE
     src/datadog/cerr_logger.cpp
     src/datadog/clock.cpp
     src/datadog/collector.cpp
@@ -132,7 +137,7 @@ target_sources(dd_trace_cpp PRIVATE
 )
 
 # This library's public headers are just its source headers.
-target_sources(dd_trace_cpp PUBLIC
+target_sources(dd_trace_cpp-objects PUBLIC
   FILE_SET public_headers
   TYPE HEADERS
   BASE_DIRS src/
@@ -193,20 +198,30 @@ target_sources(dd_trace_cpp PUBLIC
   src/datadog/w3c_propagation.h
 )
 
-add_dependencies(dd_trace_cpp curl)
+add_dependencies(dd_trace_cpp-objects curl)
 
-# Make the build libcurl visible to dd_trace_cpp, and its dependents.
-target_include_directories(dd_trace_cpp PUBLIC ${CMAKE_BINARY_DIR}/include)
+# Make the build libcurl visible.
+include_directories(${CMAKE_BINARY_DIR}/include)
 
 # Linking this library requires libcurl and threads.
 find_package(Threads REQUIRED)
-target_link_libraries(dd_trace_cpp PUBLIC ${CMAKE_BINARY_DIR}/lib/libcurl.a PUBLIC Threads::Threads ${COVERAGE_LIBRARIES})
+target_link_libraries(dd_trace_cpp-objects PUBLIC ${CMAKE_BINARY_DIR}/lib/libcurl.a PUBLIC Threads::Threads ${COVERAGE_LIBRARIES})
 
 # When installing, install the library and its public headers.
-
-install(TARGETS dd_trace_cpp
+install(TARGETS dd_trace_cpp-objects
   FILE_SET public_headers)
 
+# Produce both shared and static versions of the library.
+add_library(dd_trace_cpp-shared SHARED $<TARGET_OBJECTS:dd_trace_cpp-objects>)
+set_target_properties(dd_trace_cpp-shared PROPERTIES OUTPUT_NAME "dd_trace_cpp")
+add_dependencies(dd_trace_cpp-shared dd_trace_cpp-objects)
+target_link_libraries(dd_trace_cpp-shared dd_trace_cpp-objects)
+
+add_library(dd_trace_cpp-static STATIC $<TARGET_OBJECTS:dd_trace_cpp-objects>)
+set_target_properties(dd_trace_cpp-static PROPERTIES OUTPUT_NAME "dd_trace_cpp")
+add_dependencies(dd_trace_cpp-static dd_trace_cpp-objects)
+target_link_libraries(dd_trace_cpp-static dd_trace_cpp-objects)
+
 if(BUILD_TESTING)
   add_subdirectory(test)
 endif()

example/CMakeLists.txt

@@ -1,3 +1,3 @@
 add_executable(example hasher.cpp)
 
-target_link_libraries(example dd_trace_cpp)
+target_link_libraries(example dd_trace_cpp-static)

fuzz/w3c-propagation/CMakeLists.txt

@@ -1,3 +1,4 @@
 add_executable(fuzz fuzz.cpp)
 
-target_link_libraries(fuzz dd_trace_cpp)
+add_dependencies(fuzz dd_trace_cpp-static)
+target_link_libraries(fuzz dd_trace_cpp-static)

src/datadog/parse_util.cpp

@@ -108,5 +108,10 @@ bool starts_with(StringView subject, StringView prefix) {
          prefix.end();
 }
 
+void to_lower(std::string& text) {
+  std::transform(text.begin(), text.end(), text.begin(),
+                 [](unsigned char ch) { return std::tolower(ch); });
+}
+
 }  // namespace tracing
 }  // namespace datadog

src/datadog/parse_util.h

@@ -36,5 +36,8 @@ Expected<double> parse_double(StringView input);
 // Return whether the specified `prefix` is a prefix of the specified `subject`.
 bool starts_with(StringView subject, StringView prefix);
 
+// Convert the specified `text` to lower case in-place.
+void to_lower(std::string& text);
+
 }  // namespace tracing
 }  // namespace datadog

src/datadog/propagation_style.cpp

@@ -3,6 +3,7 @@
 #include <cassert>
 
 #include "json.hpp"
+#include "parse_util.h"
 
 namespace datadog {
 namespace tracing {
@@ -31,5 +32,24 @@ nlohmann::json to_json(const std::vector<PropagationStyle>& styles) {
   return styles_json;
 }
 
+Optional<PropagationStyle> parse_propagation_style(StringView text) {
+  auto token = std::string{text};
+  to_lower(token);
+
+  // Note: Make sure that these strings are consistent (modulo case) with
+  // `to_json`, above.
+  if (token == "datadog") {
+    return PropagationStyle::DATADOG;
+  } else if (token == "b3" || token == "b3multi") {
+    return PropagationStyle::B3;
+  } else if (token == "tracecontext") {
+    return PropagationStyle::W3C;
+  } else if (token == "none") {
+    return PropagationStyle::NONE;
+  }
+
+  return nullopt;
+}
+
 }  // namespace tracing
 }  // namespace datadog

src/datadog/propagation_style.h

@@ -8,6 +8,8 @@
 #include <vector>
 
 #include "json_fwd.hpp"
+#include "optional.h"
+#include "string_view.h"
 
 namespace datadog {
 namespace tracing {
@@ -28,5 +30,7 @@ enum class PropagationStyle {
 nlohmann::json to_json(PropagationStyle style);
 nlohmann::json to_json(const std::vector<PropagationStyle>& styles);
 
+Optional<PropagationStyle> parse_propagation_style(StringView text);
+
 }  // namespace tracing
 }  // namespace datadog

src/datadog/span.h

@@ -76,7 +76,8 @@ class Span {
        const Clock& clock);
   Span(const Span&) = delete;
   Span(Span&&) = default;
-  Span& operator=(Span&&) = default;
+  Span& operator=(Span&&) = delete;
+  Span& operator=(const Span&) = delete;
 
   // Finish this span and submit it to the associated trace segment.  If
   // `set_end_time` has not been called on this span, then set this span's end

src/datadog/span_sampler_config.cpp

@@ -245,13 +245,9 @@ Expected<FinalizedSpanSamplerConfig> finalize_config(
 }
 
 nlohmann::json to_json(const FinalizedSpanSamplerConfig::Rule &rule) {
-  auto result = nlohmann::json::object({
-      {"service", rule.service},
-      {"name", rule.name},
-      {"resource", rule.resource},
-      {"sample_rate", double(rule.sample_rate)},
-  });
-
+  // Get the base class's fields, then add our own.
+  auto result = static_cast<const SpanMatcher &>(rule).to_json();
+  result["sample_rate"] = double(rule.sample_rate);
   if (rule.max_per_second) {
     result["max_per_second"] = *rule.max_per_second;
   }

src/datadog/trace_sampler_config.cpp

@@ -184,12 +184,10 @@ Expected<FinalizedTraceSamplerConfig> finalize_config(
 }
 
 nlohmann::json to_json(const FinalizedTraceSamplerConfig::Rule &rule) {
-  return nlohmann::json::object({
-      {"service", rule.service},
-      {"name", rule.name},
-      {"resource", rule.resource},
-      {"sample_rate", double(rule.sample_rate)},
-  });
+  // Get the base class's fields, then add our own.
+  auto result = static_cast<const SpanMatcher &>(rule).to_json();
+  result["sample_rate"] = double(rule.sample_rate);
+  return result;
 }
 
 }  // namespace tracing