Add interned string stats in debug command

src/commands.cc

@@ -805,7 +805,7 @@ const CommandDesc debug_cmd = {
     PerArgumentCommandCompleter({
         [](const Context& context, CompletionFlags flags,
            const String& prefix, ByteCount cursor_pos) -> Completions {
-               auto c = {"info", "buffers", "options", "memory"};
+               auto c = {"info", "buffers", "options", "memory", "interned-strings"};
                return { 0_byte, cursor_pos, complete(prefix, cursor_pos, c) };
     } }),
     [](const ParametersParser& parser, Context& context)
@@ -835,13 +835,17 @@ const CommandDesc debug_cmd = {
             {
                 size_t count = domain_allocated_bytes[domain];
                 total += count;
-                write_debug(domain_name((MemoryDomain)domain) + (": " + to_string(count)));
+                write_debug("  "_sv + domain_name((MemoryDomain)domain) + ": " + to_string(count));
             }
-            write_debug("Total: " + to_string(total));
+            write_debug("  Total: " + to_string(total));
             #if defined(__GLIBC__)
-            write_debug("Malloced: " + to_string(mallinfo().uordblks));
+            write_debug("  Malloced: " + to_string(mallinfo().uordblks));
             #endif
         }
+        else if (parser[0] == "interned-strings")
+        {
+            StringRegistry::instance().debug_stats();
+        }
         else
             throw runtime_error("unknown debug command '" + parser[0] + "'");
     }

src/interned_string.cc

@@ -1,8 +1,28 @@
 #include "interned_string.hh"
+#include "debug.hh"
 
 namespace Kakoune
 {
 
+void StringRegistry::debug_stats() const
+{
+    write_debug("Interned Strings stats:");
+    write_debug("  slots: " + to_string(m_storage.size()) + " allocated, " + to_string(m_free_slots.size()) + " free");
+    size_t total_refcount = 0;
+    size_t total_size = 0;
+    size_t count = 0;
+    for (auto& st : m_storage)
+    {
+        if (st.refcount == 0)
+            continue;
+        total_refcount += st.refcount;
+        total_size += st.data.size();
+        ++count;
+    }
+    write_debug("  data size: " + to_string(total_size) + ", mean: " + to_string((float)total_size/count));
+    write_debug("  refcounts: " + to_string(total_refcount) + ", mean: " + to_string((float)total_refcount/count));
+}
+
 InternedString StringRegistry::acquire(StringView str)
 {
     auto it = m_slot_map.find(str);

src/interned_string.hh

@@ -13,6 +13,8 @@ class InternedString;
 
 class StringRegistry : public Singleton<StringRegistry>
 {
+public:
+    void debug_stats() const;
 private:
     friend class InternedString;