wip(fixup): add ifdef linux

* include/datadog/tracer.h
* include/datadog/tracer_signature.h
* src/datadog/tracer.cpp

Author: elsa

include/datadog/tracer.h

@@ -10,7 +10,9 @@
 // obtained from a `TracerConfig` via the `finalize_config` function.  See
 // `tracer_config.h`.
 
+#ifdef __linux__
 #include <datadog/tls_storage.h>
+#endif
 
 #include <cstddef>
 #include <memory>
@@ -25,9 +27,11 @@
 #include "tracer_config.h"
 #include "tracer_signature.h"
 
+#ifdef __linux__
 extern const void* elastic_apm_profiling_correlation_process_storage_v1;
 extern thread_local struct datadog::tracing::TLSStorage*
     elastic_apm_profiling_correlation_tls_v1;
+#endif
 
 namespace datadog {
 namespace tracing {
@@ -111,7 +115,9 @@ class Tracer {
   std::string config() const;
 
  private:
+#ifdef __linux__
   void correlate(const Span& span);
+#endif
   void store_config();
 };
 

include/datadog/tracer_signature.h

@@ -19,10 +19,13 @@
 //    polling the Datadog Agent. See
 //    `RemoteConfigurationManager::process_response` in `remote_config.h`.
 
+#ifdef __linux__
 #include <cstring>
 #include <memory>
-#include <string>
 #include <vector>
+#endif
+
+#include <string>
 
 #include "runtime_id.h"
 #include "string_view.h"
@@ -34,6 +37,7 @@
 namespace datadog {
 namespace tracing {
 
+#ifdef __linux__
 namespace {
 void write_utf8_string(std::vector<uint8_t>& buffer, const std::string& str) {
   uint32_t length = str.length();
@@ -42,6 +46,7 @@ void write_utf8_string(std::vector<uint8_t>& buffer, const std::string& str) {
   buffer.insert(buffer.end(), str.begin(), str.end());
 }
 }  // namespace
+#endif
 
 struct TracerSignature {
   RuntimeID runtime_id;
@@ -60,6 +65,9 @@ struct TracerSignature {
         library_language("cpp"),
         library_language_version(DD_TRACE_STRINGIFY(__cplusplus), 6) {}
 
+#ifdef __linux__
+  // The process correlation storage contains information needed to
+  // correlate traces to profiles generated by dd-otel-host-profiler.
   const std::unique_ptr<uint8_t*> generate_process_correlation_storage() {
     std::vector<uint8_t> buffer;
 
@@ -81,6 +89,7 @@ struct TracerSignature {
     memcpy(res, buffer.data(), buffer.size());
     return std::make_unique<uint8_t*>(res);
   }
+#endif
 };
 
 }  // namespace tracing

src/datadog/tracer.cpp

@@ -13,7 +13,9 @@
 
 #include <algorithm>
 #include <cassert>
+#ifdef __linux__
 #include <memory>
+#endif
 
 #include "config_manager.h"
 #include "datadog_agent.h"
@@ -30,11 +32,13 @@
 #include "trace_sampler.h"
 #include "w3c_propagation.h"
 
+#ifdef __linux__
 const void* elastic_apm_profiling_correlation_process_storage_v1 = nullptr;
 thread_local struct datadog::tracing::TLSStorage*
     elastic_apm_profiling_correlation_tls_v1 = nullptr;
 thread_local std::unique_ptr<datadog::tracing::TLSStorage> tls_info_holder =
     nullptr;
+#endif
 
 namespace datadog {
 namespace tracing {
@@ -101,10 +105,12 @@ Tracer::Tracer(const FinalizedTracerConfig& config,
     }
   }
 
+#ifdef __linux__
   // TODO: change the way this is done to handle programs that fork.
   // TODO: add a flag to disable this by default.
   elastic_apm_profiling_correlation_process_storage_v1 =
       *signature_.generate_process_correlation_storage();
+#endif
 
   if (config.log_on_startup) {
     logger_->log_startup([configuration = this->config()](std::ostream& log) {
@@ -115,6 +121,7 @@ Tracer::Tracer(const FinalizedTracerConfig& config,
   store_config();
 }
 
+#ifdef __linux__
 void Tracer::correlate(const Span& span) {
   tls_info_holder = std::make_unique<datadog::tracing::TLSStorage>();
   elastic_apm_profiling_correlation_tls_v1 = tls_info_holder.get();
@@ -137,6 +144,7 @@ void Tracer::correlate(const Span& span) {
 
   tls_data->valid = 1;
 }
+#endif
 
 std::string Tracer::config() const {
   // clang-format off
@@ -228,7 +236,9 @@ Span Tracer::create_span(const SpanConfig& config) {
   Span span{span_data_ptr, segment,
             [generator = generator_]() { return generator->span_id(); },
             clock_};
+#ifdef __linux__
   correlate(span);
+#endif
   return span;
 }
 
@@ -431,7 +441,9 @@ Expected<Span> Tracer::extract_span(const DictReader& reader,
   Span span{span_data_ptr, segment,
             [generator = generator_]() { return generator->span_id(); },
             clock_};
+#ifdef __linux__
   correlate(span);
+#endif
   return span;
 }