src: implement debug output utilities

Implement utilities for easier debugging of Node.js core code,
inspired by the HTTP/2 debugging code. Debugging is, however,
implemented at runtime rather than at compile time, controlled
through a new `NODE_DEBUG_NATIVE=categories` environment variable.

The runtime overhead in the debugging-disabled case amounts to
1 well-cachable one-byte read per debug call.

PR-URL: https://github.com/nodejs/node/pull/20987
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/src/env.h b/src/env.h
index 15d417ba60..c17cc59b5b 100644
--- a/src/env.h
+++ b/src/env.h
@@ -398,6 +398,19 @@ struct ContextInfo {
   bool is_default = false;
 };
 
+// Listing the AsyncWrap provider types first enables us to cast directly
+// from a provider type to a debug category. Currently no other debug
+// categories are available.
+#define DEBUG_CATEGORY_NAMES(V) \
+    NODE_ASYNC_PROVIDER_TYPES(V)
+
+enum class DebugCategory {
+#define V(name) name,
+  DEBUG_CATEGORY_NAMES(V)
+#undef V
+  CATEGORY_COUNT
+};
+
 class Environment {
  public:
   class AsyncHooks {
@@ -654,6 +667,10 @@ class Environment {
   inline http2::Http2State* http2_state() const;
   inline void set_http2_state(std::unique_ptr<http2::Http2State> state);
 
+  inline bool debug_enabled(DebugCategory category) const;
+  inline void set_debug_enabled(DebugCategory category, bool enabled);
+  void set_debug_categories(const std::string& cats, bool enabled);
+
   inline AliasedBuffer<double, v8::Float64Array>* fs_stats_field_array();
 
   // stat fields contains twice the number of entries because `fs.StatWatcher`
@@ -853,6 +870,8 @@ class Environment {
   bool http_parser_buffer_in_use_ = false;
   std::unique_ptr<http2::Http2State> http2_state_;
 
+  bool debug_enabled_[static_cast<int>(DebugCategory::CATEGORY_COUNT)] = {0};
+
   AliasedBuffer<double, v8::Float64Array> fs_stats_field_array_;
 
   std::vector<std::unique_ptr<fs::FileHandleReadWrap>>