Fix #326. Crash was caused by rp_methods holding a reference to Profi…

…le ruby objects which were moved during GC compaction phase.

ext/ruby_prof/rp_method.c

@@ -4,6 +4,7 @@
 #include "rp_allocation.h"
 #include "rp_call_trees.h"
 #include "rp_method.h"
+#include "rp_profile.h"
 
 VALUE cRpMethodInfo;
 
@@ -125,7 +126,7 @@ prof_method_t* prof_get_method(VALUE self)
     return result;
 }
 
-prof_method_t* prof_method_create(VALUE profile, VALUE klass, VALUE msym, VALUE source_file, int source_line)
+prof_method_t* prof_method_create(struct prof_profile_t* profile, VALUE klass, VALUE msym, VALUE source_file, int source_line)
 {
     prof_method_t* result = ALLOC(prof_method_t);
     result->profile = profile;
@@ -204,14 +205,16 @@ void prof_method_mark(void* data)
 
     prof_method_t* method = (prof_method_t*)data;
 
-    if (method->profile != Qnil)
-        rb_gc_mark_movable(method->profile);
-
     if (method->object != Qnil)
-        rb_gc_mark_movable(method->object);
+      rb_gc_mark_movable(method->object);
+
+    // Mark the profile to keep it alive. Can't call prof_profile_mark because that would
+    // cause recursion
+    if (method->profile && method->profile->object != Qnil)
+        rb_gc_mark(method->profile->object);
 
-    rb_gc_mark_movable(method->klass_name);
-    rb_gc_mark_movable(method->method_name);
+    rb_gc_mark(method->klass_name);
+    rb_gc_mark(method->method_name);
     rb_gc_mark(method->source_file);
 
     if (method->klass != Qnil)
@@ -225,14 +228,13 @@ void prof_method_compact(void* data)
 {
     prof_method_t* method = (prof_method_t*)data;
     method->object = rb_gc_location(method->object);
-    method->profile = rb_gc_location(method->profile);
     method->klass_name = rb_gc_location(method->klass_name);
     method->method_name = rb_gc_location(method->method_name);
 }
 
 static VALUE prof_method_allocate(VALUE klass)
 {
-    prof_method_t* method_data = prof_method_create(Qnil, Qnil, Qnil, Qnil, 0);
+    prof_method_t* method_data = prof_method_create(NULL, Qnil, Qnil, Qnil, 0);
     method_data->object = prof_method_wrap(method_data);
     return method_data->object;
 }

ext/ruby_prof/rp_method.h

@@ -18,11 +18,14 @@ enum {
     kOtherSingleton = 0x10                    // Singleton of unknown object
 };
 
+// Don't want to include ruby_prof.h to avoid a circular reference
+struct prof_profile_t;
+
 // Profiling information for each method.
 // Excluded methods have no call_trees, source_klass, or source_file.
 typedef struct prof_method_t
 {
-    VALUE profile;                          // Profile this method is associated with - needed for mark phase
+    struct prof_profile_t* profile;                  // Profile this method is associated with - needed for mark phase
     struct prof_call_trees_t* call_trees;   // Call infos that call this method
     st_table* allocations_table;            // Tracks object allocations
 
@@ -51,7 +54,7 @@ prof_method_t* method_table_lookup(st_table* table, st_data_t key);
 size_t method_table_insert(st_table* table, st_data_t key, prof_method_t* val);
 void method_table_free(st_table* table);
 void prof_method_table_merge(st_table* self, st_table* other);
-prof_method_t* prof_method_create(VALUE profile, VALUE klass, VALUE msym, VALUE source_file, int source_line);
+prof_method_t* prof_method_create(struct prof_profile_t* profile, VALUE klass, VALUE msym, VALUE source_file, int source_line);
 prof_method_t* prof_get_method(VALUE self);
 
 VALUE prof_method_wrap(prof_method_t* result);

ext/ruby_prof/rp_profile.c

@@ -105,7 +105,7 @@ static int excludes_method(st_data_t key, prof_profile_t* profile)
 
 static prof_method_t* create_method(prof_profile_t* profile, st_data_t key, VALUE klass, VALUE msym, VALUE source_file, int source_line)
 {
-    prof_method_t* result = prof_method_create(profile->object, klass, msym, source_file, source_line);
+    prof_method_t* result = prof_method_create(profile, klass, msym, source_file, source_line);
     method_table_insert(profile->last_thread_data->method_table, result->key, result);
 
     return result;
@@ -863,7 +863,7 @@ static VALUE prof_exclude_method(VALUE self, VALUE klass, VALUE msym)
 
     if (!method)
     {
-        method = prof_method_create(self, klass, msym, Qnil, 0);
+        method = prof_method_create(profile, klass, msym, Qnil, 0);
         method_table_insert(profile->exclude_methods_tbl, method->key, method);
     }