src: make minor improvements to EnabledDebugList

Change the underlying type of DebugCategory to unsigned int so that it
can be safely cast to an unsigned type without having to worry about
negative values, removing the need for the DCHECK_GE statements.

To fully benefit from type safety, remove DebugCategory::CATEGORY_COUNT
and instead add a constexpr kDebugCategoryCount.

Change the list of enabled categories from a bool array to a
std::bitset, which is slightly more space-efficient.

Use std::bitset::set() to enable categories, removing the need for the
DCHECK_LT in EnabledDebugList::set_enabled().

Note: intentionally do not use std::bitset::test() in
EnabledDebugList::enabled() because it might be in a hot path and,
unlike DCHECK_LT, std::bitset::test() may incur a runtime cost.

Remove the second argument from EnabledDebugList::set_enabled() and
EnabledDebugList::Parse() because it was always set to true.

Author: tniessen

src/debug_utils.cc

@@ -63,10 +63,10 @@ void EnabledDebugList::Parse(std::shared_ptr<KVStore> env_vars,
                              v8::Isolate* isolate) {
   std::string cats;
   credentials::SafeGetenv("NODE_DEBUG_NATIVE", &cats, env_vars, isolate);
-  Parse(cats, true);
+  Parse(cats);
 }
 
-void EnabledDebugList::Parse(const std::string& cats, bool enabled) {
+void EnabledDebugList::Parse(const std::string& cats) {
   std::string debug_categories = cats;
   while (!debug_categories.empty()) {
     std::string::size_type comma_pos = debug_categories.find(',');
@@ -76,7 +76,7 @@ void EnabledDebugList::Parse(const std::string& cats, bool enabled) {
   {                                                                            \
     static const std::string available_category = ToLower(#name);              \
     if (available_category.find(wanted) != std::string::npos)                  \
-      set_enabled(DebugCategory::name, enabled);                               \
+      set_enabled(DebugCategory::name);                                        \
   }
 
     DEBUG_CATEGORY_NAMES(V)

src/debug_utils.h

@@ -7,6 +7,7 @@
 #include "util.h"
 
 #include <algorithm>
+#include <bitset>
 #include <sstream>
 #include <string>
 
@@ -51,20 +52,21 @@ void NODE_EXTERN_PRIVATE FWrite(FILE* file, const std::string& str);
   V(WASI)                                                                      \
   V(MKSNAPSHOT)
 
-enum class DebugCategory {
+enum class DebugCategory : unsigned int {
 #define V(name) name,
   DEBUG_CATEGORY_NAMES(V)
 #undef V
-      CATEGORY_COUNT
 };
 
+#define V(name) +1
+constexpr unsigned int kDebugCategoryCount = DEBUG_CATEGORY_NAMES(V);
+#undef V
+
 class NODE_EXTERN_PRIVATE EnabledDebugList {
  public:
   bool enabled(DebugCategory category) const {
-    DCHECK_GE(static_cast<int>(category), 0);
-    DCHECK_LT(static_cast<int>(category),
-              static_cast<int>(DebugCategory::CATEGORY_COUNT));
-    return enabled_[static_cast<int>(category)];
+    DCHECK_LT(static_cast<unsigned int>(category), kDebugCategoryCount);
+    return enabled_[static_cast<unsigned int>(category)];
   }
 
   // Uses NODE_DEBUG_NATIVE to initialize the categories. The env_vars variable
@@ -75,15 +77,12 @@ class NODE_EXTERN_PRIVATE EnabledDebugList {
 
  private:
   // Set all categories matching cats to the value of enabled.
-  void Parse(const std::string& cats, bool enabled);
-  void set_enabled(DebugCategory category, bool enabled) {
-    DCHECK_GE(static_cast<int>(category), 0);
-    DCHECK_LT(static_cast<int>(category),
-              static_cast<int>(DebugCategory::CATEGORY_COUNT));
-    enabled_[static_cast<int>(category)] = true;
+  void Parse(const std::string& cats);
+  void set_enabled(DebugCategory category) {
+    enabled_.set(static_cast<unsigned int>(category));
   }
 
-  bool enabled_[static_cast<int>(DebugCategory::CATEGORY_COUNT)] = {false};
+  std::bitset<kDebugCategoryCount> enabled_;
 };
 
 template <typename... Args>