From 645cd94d9a2383f973ae2fd83fef7024ae59c679 Mon Sep 17 00:00:00 2001
From: Chris Seaton <chris.seaton@shopify.com>
Date: Wed, 7 Dec 2022 19:09:30 -0600
Subject: [PATCH] Add debug counters to RubyVM.stat (#6086)

* Add debug counters to RubyVM.stat

* Use SIZET2NUM

Co-author: Nobuyoshi Nakada <nobu@ruby-lang.org>

* Prefix debug_counter_names
---
 debug_counter.c |  8 ++++----
 vm.c            | 19 +++++++++++++++++++
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/debug_counter.c b/debug_counter.c
index cbaf15d496..463bebf849 100644
--- a/debug_counter.c
+++ b/debug_counter.c
@@ -16,7 +16,7 @@
 
 #if USE_DEBUG_COUNTER
 
-static const char *const debug_counter_names[] = {
+const char *const rb_debug_counter_names[] = {
 #define DEBUG_COUNTER_NAME_EMPTY "" /* Suppress -Wstring-concatenation */
     DEBUG_COUNTER_NAME_EMPTY
 #undef DEBUG_COUNTER_NAME_EMPTY
@@ -26,7 +26,7 @@ static const char *const debug_counter_names[] = {
 };
 
 MJIT_SYMBOL_EXPORT_BEGIN
-size_t rb_debug_counter[numberof(debug_counter_names)];
+size_t rb_debug_counter[numberof(rb_debug_counter_names)];
 void rb_debug_counter_add_atomic(enum rb_debug_counter_type type, int add);
 MJIT_SYMBOL_EXPORT_END
 
@@ -67,7 +67,7 @@ ruby_debug_counter_get(const char **names_ptr, size_t *counters_ptr)
     int i;
     if (names_ptr != NULL) {
         for (i=0; i<RB_DEBUG_COUNTER_MAX; i++) {
-            names_ptr[i] = debug_counter_names[i];
+            names_ptr[i] = rb_debug_counter_names[i];
         }
     }
     if (counters_ptr != NULL) {
@@ -97,7 +97,7 @@ rb_debug_counter_show_results(const char *msg)
         fprintf(stderr, "[RUBY_DEBUG_COUNTER]\t%d %s\n", getpid(), msg);
         for (i=0; i<RB_DEBUG_COUNTER_MAX; i++) {
             fprintf(stderr, "[RUBY_DEBUG_COUNTER]\t%-30s\t%'14"PRIuSIZE"\n",
-                    debug_counter_names[i],
+                    rb_debug_counter_names[i],
                     rb_debug_counter[i]);
         }
     }
diff --git a/vm.c b/vm.c
index 3181f97123..d62b2f0d48 100644
--- a/vm.c
+++ b/vm.c
@@ -66,6 +66,8 @@ MJIT_FUNC_EXPORTED
 #endif
 VALUE vm_exec(rb_execution_context_t *, bool);
 
+extern const char *const rb_debug_counter_names[];
+
 PUREFUNC(static inline const VALUE *VM_EP_LEP(const VALUE *));
 static inline const VALUE *
 VM_EP_LEP(const VALUE *ep)
@@ -578,6 +580,8 @@ rb_dtrace_setup(rb_execution_context_t *ec, VALUE klass, ID id,
  *      :global_cvar_state=>27
  *    }
  *
+ *  If <tt>USE_DEBUG_COUNTER</tt> is enabled, debug counters will be included.
+ *
  *  The contents of the hash are implementation specific and may be changed in
  *  the future.
  *
@@ -622,6 +626,21 @@ vm_stat(int argc, VALUE *argv, VALUE self)
     SET(next_shape_id, (rb_serial_t)GET_VM()->next_shape_id);
 #undef SET
 
+#if USE_DEBUG_COUNTER
+    ruby_debug_counter_show_at_exit(FALSE);
+    for (size_t i = 0; i < RB_DEBUG_COUNTER_MAX; i++) {
+        const VALUE name = rb_sym_intern_ascii_cstr(rb_debug_counter_names[i]);
+        const VALUE boxed_value = SIZET2NUM(rb_debug_counter[i]);
+
+        if (key == name) {
+            return boxed_value;
+        }
+        else if (hash != Qnil) {
+            rb_hash_aset(hash, name, boxed_value);
+        }
+    }
+#endif
+
     if (!NIL_P(key)) { /* matched key should return above */
         rb_raise(rb_eArgError, "unknown key: %"PRIsVALUE, rb_sym2str(key));
     }