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Implement Write Barrier and dsize for FFI::Struct #1007

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Merged
larskanis merged 1 commit into from
Mar 6, 2023
Merged

Implement Write Barrier and dsize for FFI::Struct #1007

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79 changes: 50 additions & 29 deletions ext/ffi_c/Struct.c
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Original file line number Diff line number Diff line change
Expand Up @@ -63,19 +63,23 @@ typedef struct InlineArray_ {

static void struct_mark(void *data);
static void struct_free(void *data);
static size_t struct_memsize(const void *);
static VALUE struct_class_layout(VALUE klass);
static void struct_malloc(Struct* s);
static void struct_malloc(VALUE self, Struct* s);
static void inline_array_mark(void *);
static void store_reference_value(StructField* f, Struct* s, VALUE value);
static size_t inline_array_memsize(const void *);
static void store_reference_value(VALUE self, StructField* f, Struct* s, VALUE value);

const rb_data_type_t rbffi_struct_data_type = { /* extern */
.wrap_struct_name = "FFI::Struct",
.function = {
.dmark = struct_mark,
.dfree = struct_free,
.dsize = NULL,
.dsize = struct_memsize,
},
.flags = 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.
.flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED
};
VALUE rbffi_StructClass = Qnil;

Expand All @@ -99,8 +103,8 @@ struct_allocate(VALUE klass)
Struct* s;
VALUE obj = TypedData_Make_Struct(klass, Struct, &rbffi_struct_data_type, s);

s->rbPointer = Qnil;
s->rbLayout = Qnil;
RB_OBJ_WRITE(obj, &s->rbPointer, Qnil);
RB_OBJ_WRITE(obj, &s->rbLayout, Qnil);

return obj;
}
Expand All @@ -125,9 +129,10 @@ struct_initialize(int argc, VALUE* argv, VALUE self)

/* Call up into ruby code to adjust the layout */
if (nargs > 1) {
s->rbLayout = rb_funcall2(CLASS_OF(self), id_layout, (int) RARRAY_LEN(rest), RARRAY_PTR(rest));
VALUE rbLayout = rb_funcall2(CLASS_OF(self), id_layout, (int) RARRAY_LEN(rest), RARRAY_PTR(rest));
RB_OBJ_WRITE(self, &s->rbLayout, rbLayout);
} else {
s->rbLayout = struct_class_layout(klass);
RB_OBJ_WRITE(self, &s->rbLayout, struct_class_layout(klass));
}

if (!rb_obj_is_kind_of(s->rbLayout, rbffi_StructLayoutClass)) {
Expand All @@ -138,9 +143,9 @@ struct_initialize(int argc, VALUE* argv, VALUE self)

if (rbPointer != Qnil) {
s->pointer = MEMORY(rbPointer);
s->rbPointer = rbPointer;
RB_OBJ_WRITE(self, &s->rbPointer, rbPointer);
} else {
struct_malloc(s);
struct_malloc(self, s);
}

return self;
Expand All @@ -163,7 +168,7 @@ struct_initialize_copy(VALUE self, VALUE other)
return self;
}

dst->rbLayout = src->rbLayout;
RB_OBJ_WRITE(self, &dst->rbLayout, src->rbLayout);
dst->layout = src->layout;

/*
Expand All @@ -172,17 +177,20 @@ struct_initialize_copy(VALUE self, VALUE other)
* be longer than just this struct.
*/
if (src->pointer->address != NULL) {
dst->rbPointer = rbffi_MemoryPointer_NewInstance(1, src->layout->size, false);
RB_OBJ_WRITE(self, &dst->rbPointer, rbffi_MemoryPointer_NewInstance(1, src->layout->size, false));
dst->pointer = MEMORY(dst->rbPointer);
memcpy(dst->pointer->address, src->pointer->address, src->layout->size);
} else {
dst->rbPointer = src->rbPointer;
RB_OBJ_WRITE(self, &dst->rbPointer, src->rbPointer);
dst->pointer = src->pointer;
}

if (src->layout->referenceFieldCount > 0) {
dst->rbReferences = ALLOC_N(VALUE, dst->layout->referenceFieldCount);
memcpy(dst->rbReferences, src->rbReferences, dst->layout->referenceFieldCount * sizeof(VALUE));
for (size_t index = 0; index < dst->layout->referenceFieldCount; index++) {
RB_OBJ_WRITTEN(self, Qundef, &dst->rbReferences[index]);
}
}

return self;
Expand Down Expand Up @@ -214,7 +222,7 @@ struct_layout(VALUE self)
}

if (s->layout == NULL) {
s->rbLayout = struct_class_layout(CLASS_OF(self));
RB_OBJ_WRITE(self, &s->rbLayout, struct_class_layout(CLASS_OF(self)));
TypedData_Get_Struct(s->rbLayout, StructLayout, &rbffi_struct_layout_data_type, s->layout);
}

Expand All @@ -232,18 +240,17 @@ struct_validate(VALUE self)
}

if (s->pointer == NULL) {
struct_malloc(s);
struct_malloc(self, s);
}

return s;
}

static void
struct_malloc(Struct* s)
struct_malloc(VALUE self, Struct* s)
{
if (s->rbPointer == Qnil) {
s->rbPointer = rbffi_MemoryPointer_NewInstance(s->layout->size, 1, true);

RB_OBJ_WRITE(self, &s->rbPointer, rbffi_MemoryPointer_NewInstance(s->layout->size, 1, true));
} else if (!rb_obj_is_kind_of(s->rbPointer, rbffi_AbstractMemoryClass)) {
rb_raise(rb_eRuntimeError, "invalid pointer in struct");
}
Expand All @@ -270,9 +277,15 @@ struct_free(void *data)
xfree(s);
}

static size_t
struct_memsize(const void *data)
{
const Struct *s = (const Struct *)data;
return sizeof(Struct) + (s->layout->referenceFieldCount * sizeof(VALUE));
}

static void
store_reference_value(StructField* f, Struct* s, VALUE value)
store_reference_value(VALUE self, StructField* f, Struct* s, VALUE value)
{
if (unlikely(f->referenceIndex == -1)) {
rb_raise(rb_eRuntimeError, "put_reference_value called for non-reference type");
Expand All @@ -282,11 +295,11 @@ store_reference_value(StructField* f, Struct* s, VALUE value)
int i;
s->rbReferences = ALLOC_N(VALUE, s->layout->referenceFieldCount);
for (i = 0; i < s->layout->referenceFieldCount; ++i) {
s->rbReferences[i] = Qnil;
RB_OBJ_WRITE(self, &s->rbReferences[i], Qnil);
}
}

s->rbReferences[f->referenceIndex] = value;
RB_OBJ_WRITE(self, &s->rbReferences[f->referenceIndex], value);
}


Expand Down Expand Up @@ -371,7 +384,7 @@ struct_aset(VALUE self, VALUE fieldName, VALUE value)
}

if (f->referenceRequired) {
store_reference_value(f, s, value);
store_reference_value(self, f, s, value);
}

return value;
Expand Down Expand Up @@ -407,7 +420,7 @@ struct_set_pointer(VALUE self, VALUE pointer)
}

s->pointer = MEMORY(pointer);
s->rbPointer = pointer;
RB_OBJ_WRITE(self, &s->rbPointer, pointer);
rb_ivar_set(self, id_pointer_ivar, pointer);

return self;
Expand Down Expand Up @@ -508,9 +521,11 @@ static const rb_data_type_t inline_array_data_type = {
.function = {
.dmark = inline_array_mark,
.dfree = RUBY_TYPED_DEFAULT_FREE,
.dsize = NULL,
.dsize = inline_array_memsize,
},
.flags = 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.
.flags = RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED
};

static VALUE
Expand All @@ -520,8 +535,8 @@ inline_array_allocate(VALUE klass)
VALUE obj;

obj = TypedData_Make_Struct(klass, InlineArray, &inline_array_data_type, array);
array->rbField = Qnil;
array->rbMemory = Qnil;
RB_OBJ_WRITE(obj, &array->rbMemory, Qnil);
RB_OBJ_WRITE(obj, &array->rbField, Qnil);

return obj;
}
Expand All @@ -534,6 +549,12 @@ inline_array_mark(void *data)
rb_gc_mark(array->rbMemory);
}

static size_t
inline_array_memsize(const void *data)
{
return sizeof(InlineArray);
}

/*
* Document-method: FFI::Struct::InlineArray#initialize
* call-seq: initialize(memory, field)
Expand All @@ -547,8 +568,8 @@ inline_array_initialize(VALUE self, VALUE rbMemory, VALUE rbField)
InlineArray* array;

TypedData_Get_Struct(self, InlineArray, &inline_array_data_type, array);
array->rbMemory = rbMemory;
array->rbField = rbField;
RB_OBJ_WRITE(self, &array->rbMemory, rbMemory);
RB_OBJ_WRITE(self, &array->rbField, rbField);

TypedData_Get_Struct(rbMemory, AbstractMemory, &rbffi_abstract_memory_data_type, array->memory);
TypedData_Get_Struct(rbField, StructField, &rbffi_struct_field_data_type, array->field);
Expand Down
13 changes: 13 additions & 0 deletions spec/ffi/struct_spec.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -1027,6 +1027,19 @@ class BuggedStruct < FFI::Struct
end
end

describe "Struct memsize", skip: RUBY_ENGINE != "ruby" do
it "has a memsize function" do
base_size = ObjectSpace.memsize_of(Object.new)

c = Class.new(FFI::Struct) do
layout :b, :bool
end
struct = c.new
size = ObjectSpace.memsize_of(struct)
expect(size).to be > base_size
end
end

describe "Struct order" do
before :all do
@struct = Class.new(FFI::Struct) do
Expand Down