Add write barriers to PG::Coder and derivations

Write barrier protected objects are allowed to be promoted to the old generation, which means they only get marked on major GC. The downside is that the RB_BJ_WRITE macro MUST be used to set references, otherwise the referenced object may be garbaged collected.
larskanis · Mar 29, 2023 · 113ee1a · 113ee1a
1 parent 43b80fb
commit 113ee1a
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Showing 3 changed files with 18 additions and 16 deletions.
diff --git a/ext/pg_coder.c b/ext/pg_coder.c
@@ -35,7 +35,7 @@ pg_coder_init_encoder( VALUE self )
 		this->enc_func = NULL;
 	}
 	this->dec_func = NULL;
-	this->coder_obj = self;
+	RB_OBJ_WRITE(self, &this->coder_obj, self);
 	this->oid = 0;
 	this->format = 0;
 	this->flags = 0;
@@ -54,7 +54,7 @@ pg_coder_init_decoder( VALUE self )
 	} else {
 		this->dec_func = NULL;
 	}
-	this->coder_obj = self;
+	RB_OBJ_WRITE(self, &this->coder_obj, self);
 	this->oid = 0;
 	this->format = 0;
 	this->flags = 0;
@@ -99,7 +99,9 @@ const rb_data_type_t pg_coder_type = {
 	},
 	0,
 	0,
-	RUBY_TYPED_FREE_IMMEDIATELY,
+	// IMPORTANT: WB_PROTECTED objects must only use the RB_OBJ_WRITE()
+	// macro to update VALUE references, as to trigger write barriers.
+	RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
 };
 
 static VALUE
@@ -121,7 +123,7 @@ static const rb_data_type_t pg_composite_coder_type = {
 	},
 	&pg_coder_type,
 	0,
-	RUBY_TYPED_FREE_IMMEDIATELY,
+	RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
 };
 
 static VALUE
@@ -452,7 +454,7 @@ static const rb_data_type_t pg_coder_cfunc_type = {
 	},
 	0,
 	0,
-	RUBY_TYPED_FREE_IMMEDIATELY,
+	RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
 };
 
 VALUE

diff --git a/ext/pg_copy_coder.c b/ext/pg_copy_coder.c
@@ -55,7 +55,7 @@ static const rb_data_type_t pg_copycoder_type = {
 	},
 	&pg_coder_type,
 	0,
-	RUBY_TYPED_FREE_IMMEDIATELY,
+	RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
 };
 
 static VALUE
@@ -64,9 +64,9 @@ pg_copycoder_encoder_allocate( VALUE klass )
 	t_pg_copycoder *this;
 	VALUE self = TypedData_Make_Struct( klass, t_pg_copycoder, &pg_copycoder_type, this );
 	pg_coder_init_encoder( self );
-	this->typemap = pg_typemap_all_strings;
+	RB_OBJ_WRITE(self, &this->typemap, pg_typemap_all_strings);
 	this->delimiter = '\t';
-	this->null_string = rb_str_new_cstr("\\N");
+	RB_OBJ_WRITE(self, &this->null_string, rb_str_new_cstr("\\N"));
 	return self;
 }
 
@@ -76,9 +76,9 @@ pg_copycoder_decoder_allocate( VALUE klass )
 	t_pg_copycoder *this;
 	VALUE self = TypedData_Make_Struct( klass, t_pg_copycoder, &pg_copycoder_type, this );
 	pg_coder_init_decoder( self );
-	this->typemap = pg_typemap_all_strings;
+	RB_OBJ_WRITE(self, &this->typemap, pg_typemap_all_strings);
 	this->delimiter = '\t';
-	this->null_string = rb_str_new_cstr("\\N");
+	RB_OBJ_WRITE(self, &this->null_string, rb_str_new_cstr("\\N"));
 	return self;
 }
 
@@ -128,7 +128,7 @@ pg_copycoder_null_string_set(VALUE self, VALUE null_string)
 {
 	t_pg_copycoder *this = RTYPEDDATA_DATA(self);
 	StringValue(null_string);
-	this->null_string = null_string;
+	RB_OBJ_WRITE(self, &this->null_string, null_string);
 	return null_string;
 }
 
@@ -162,7 +162,7 @@ pg_copycoder_type_map_set(VALUE self, VALUE type_map)
 		rb_raise( rb_eTypeError, "wrong elements type %s (expected some kind of PG::TypeMap)",
 				rb_obj_classname( type_map ) );
 	}
-	this->typemap = type_map;
+	RB_OBJ_WRITE(self, &this->typemap, type_map);
 
 	return type_map;
 }

diff --git a/ext/pg_record_coder.c b/ext/pg_record_coder.c
@@ -47,7 +47,7 @@ static const rb_data_type_t pg_recordcoder_type = {
 	},
 	&pg_coder_type,
 	0,
-	RUBY_TYPED_FREE_IMMEDIATELY,
+	RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED,
 };
 
 static VALUE
@@ -56,7 +56,7 @@ pg_recordcoder_encoder_allocate( VALUE klass )
 	t_pg_recordcoder *this;
 	VALUE self = TypedData_Make_Struct( klass, t_pg_recordcoder, &pg_recordcoder_type, this );
 	pg_coder_init_encoder( self );
-	this->typemap = pg_typemap_all_strings;
+	RB_OBJ_WRITE(self, &this->typemap, pg_typemap_all_strings);
 	return self;
 }
 
@@ -66,7 +66,7 @@ pg_recordcoder_decoder_allocate( VALUE klass )
 	t_pg_recordcoder *this;
 	VALUE self = TypedData_Make_Struct( klass, t_pg_recordcoder, &pg_recordcoder_type, this );
 	pg_coder_init_decoder( self );
-	this->typemap = pg_typemap_all_strings;
+	RB_OBJ_WRITE(self, &this->typemap, pg_typemap_all_strings);
 	return self;
 }
 
@@ -90,7 +90,7 @@ pg_recordcoder_type_map_set(VALUE self, VALUE type_map)
 		rb_raise( rb_eTypeError, "wrong elements type %s (expected some kind of PG::TypeMap)",
 				rb_obj_classname( type_map ) );
 	}
-	this->typemap = type_map;
+	RB_OBJ_WRITE(self, &this->typemap, type_map);
 
 	return type_map;
 }