src: refactor and apply fixes

- Defer the initialization of the `op` variable to the `default` switch case to avoid a compiler warning.
- Use a `default` switch case with a null statement if some enum values aren't suppsed to be handled, this avoids a compiler warning.
- Migrate from librsvg's deprecated `rsvg_handle_get_dimensions()` and `rsvg_handle_render_cairo()` functions to the new `rsvg_handle_get_intrinsic_size_in_pixels()` and `rsvg_handle_render_document()` respectively.
- Avoid calling virtual methods in constructors/destructors to avoid bypassing virtual dispatch.
- Remove unused private field `backend` in the `Backend` class.
- Fix a case of use-after-free.
- Fix usage of garbage value by filling the allocated memory entirely with zeros if it's not modified.
- Fix a potential memory leak.

CHANGELOG.md

@@ -8,8 +8,16 @@ project adheres to [Semantic Versioning](http://semver.org/).
 (Unreleased)
 ==================
 ### Changed
+* Defer the initialization of the `op` variable to the `default` switch case to avoid a compiler warning. (#2229)
+* Use a `default` switch case with a null statement if some enum values aren't suppsed to be handled, this avoids a compiler warning. (#2229)
+* Migrate from librsvg's deprecated `rsvg_handle_get_dimensions()` and `rsvg_handle_render_cairo()` functions to the new `rsvg_handle_get_intrinsic_size_in_pixels()` and `rsvg_handle_render_document()` respectively. (#2229)
+* Avoid calling virtual methods in constructors/destructors to avoid bypassing virtual dispatch. (#2229)
+* Remove unused private field `backend` in the `Backend` class. (#2229)
 ### Added
 ### Fixed
+* Fix a case of use-after-free. (#2229)
+* Fix usage of garbage value by filling the allocated memory entirely with zeros if it's not modified. (#2229)
+* Fix a potential memory leak. (#2229)
 
 2.11.2
 ==================

src/Canvas.cc

@@ -133,8 +133,9 @@ NAN_METHOD(Canvas::New) {
   }
 
   if (!backend->isSurfaceValid()) {
+    const char *error = backend->getError();
     delete backend;
-    return Nan::ThrowError(backend->getError());
+    return Nan::ThrowError(error);
   }
 
   Canvas* canvas = new Canvas(backend);

src/CanvasRenderingContext2d.cc

@@ -607,8 +607,8 @@ Context2d::blur(cairo_surface_t *surface, int radius) {
   // get width, height
   int width = cairo_image_surface_get_width( surface );
   int height = cairo_image_surface_get_height( surface );
-  unsigned* precalc =
-      (unsigned*)malloc(width*height*sizeof(unsigned));
+  const unsigned int size = width * height * sizeof(unsigned);
+  unsigned* precalc = (unsigned*)malloc(size);
   cairo_surface_flush( surface );
   unsigned char* src = cairo_image_surface_get_data( surface );
   double mul=1.f/((radius*2)*(radius*2));
@@ -627,6 +627,8 @@ Context2d::blur(cairo_surface_t *surface, int radius) {
           unsigned char* pix = src;
           unsigned* pre = precalc;
 
+          bool modified = false;
+
           pix += channel;
           for (y=0;y<height;y++) {
               for (x=0;x<width;x++) {
@@ -635,10 +637,15 @@ Context2d::blur(cairo_surface_t *surface, int radius) {
                   if (y>0) tot+=pre[-width];
                   if (x>0 && y>0) tot-=pre[-width-1];
                   *pre++=tot;
+                  if (!modified) modified = true;
                   pix += 4;
               }
           }
 
+          if (!modified) {
+              memset(precalc, 0, size);
+          }
+
           // blur step.
           pix = src + (int)radius * width * 4 + (int)radius * 4 + channel;
           for (y=radius;y<height-radius;y++) {
@@ -1432,7 +1439,7 @@ NAN_GETTER(Context2d::GetGlobalCompositeOperation) {
   Context2d *context = Nan::ObjectWrap::Unwrap<Context2d>(info.This());
   cairo_t *ctx = context->context();
 
-  const char *op = "source-over";
+  const char *op{};
   switch (cairo_get_operator(ctx)) {
     // composite modes:
     case CAIRO_OPERATOR_CLEAR: op = "clear"; break;
@@ -1469,6 +1476,7 @@ NAN_GETTER(Context2d::GetGlobalCompositeOperation) {
     case CAIRO_OPERATOR_HSL_LUMINOSITY: op = "luminosity"; break;
     // non-standard:
     case CAIRO_OPERATOR_SATURATE: op = "saturate"; break;
+    default: op = "source-over";
   }
 
   info.GetReturnValue().Set(Nan::New(op).ToLocalChecked());
@@ -2507,6 +2515,7 @@ Context2d::setTextPath(double x, double y) {
       pango_layout_get_pixel_extents(_layout, NULL, &logical_rect);
       x -= logical_rect.width;
       break;
+    default: ;
   }
 
   y -= getBaselineAdjustment(_layout, state->textBaseline);

src/Image.cc

@@ -1192,11 +1192,13 @@ Image::loadSVGFromBuffer(uint8_t *buf, unsigned len) {
     return CAIRO_STATUS_READ_ERROR;
   }
 
-  RsvgDimensionData *dims = new RsvgDimensionData();
-  rsvg_handle_get_dimensions(_rsvg, dims);
+  double d_width;
+  double d_height;
 
-  width = naturalWidth = dims->width;
-  height = naturalHeight = dims->height;
+  rsvg_handle_get_intrinsic_size_in_pixels(_rsvg, &d_width, &d_height);
+
+  width = naturalWidth = d_width;
+  height = naturalHeight = d_height;
 
   status = renderSVGToSurface();
   if (status != CAIRO_STATUS_SUCCESS) {
@@ -1232,7 +1234,13 @@ Image::renderSVGToSurface() {
     return status;
   }
 
-  gboolean render_ok = rsvg_handle_render_cairo(_rsvg, cr);
+  RsvgRectangle viewport = {
+    .x = 0,
+    .y = 0,
+    .width = static_cast<double>(width),
+    .height = static_cast<double>(height),
+  };
+  gboolean render_ok = rsvg_handle_render_document(_rsvg, cr, &viewport, nullptr);
   if (!render_ok) {
     g_object_unref(_rsvg);
     cairo_destroy(cr);

src/backend/Backend.cc

@@ -9,7 +9,7 @@ Backend::Backend(std::string name, int width, int height)
 
 Backend::~Backend()
 {
-  this->destroySurface();
+  Backend::destroySurface();
 }
 
 void Backend::init(const Nan::FunctionCallbackInfo<v8::Value> &info) {
@@ -97,8 +97,7 @@ bool Backend::isSurfaceValid(){
 
 BackendOperationNotAvailable::BackendOperationNotAvailable(Backend* backend,
   std::string operation_name)
-  : backend(backend)
-  , operation_name(operation_name)
+  : operation_name(operation_name)
 {
   msg = "operation " + operation_name +
     " not supported by backend " + backend->getName();

src/backend/Backend.h

@@ -57,7 +57,6 @@ class Backend : public Nan::ObjectWrap
 class BackendOperationNotAvailable: public std::exception
 {
   private:
-    Backend* backend;
     std::string operation_name;
     std::string msg;
 

src/backend/PdfBackend.cc

@@ -8,7 +8,7 @@ using namespace v8;
 
 PdfBackend::PdfBackend(int width, int height)
   : Backend("pdf", width, height) {
-  createSurface();
+  PdfBackend::createSurface();
 }
 
 PdfBackend::~PdfBackend() {

src/backend/SvgBackend.cc

@@ -9,7 +9,7 @@ using namespace v8;
 
 SvgBackend::SvgBackend(int width, int height)
   : Backend("svg", width, height) {
-  createSurface();
+  SvgBackend::createSurface();
 }
 
 SvgBackend::~SvgBackend() {

src/register_font.cc

@@ -304,6 +304,7 @@ get_pango_font_description(unsigned char* filepath) {
       }
 
       pango_font_description_set_family_static(desc, family);
+      free(family);
       pango_font_description_set_weight(desc, get_pango_weight(table->usWeightClass));
       pango_font_description_set_stretch(desc, get_pango_stretch(table->usWidthClass));
       pango_font_description_set_style(desc, get_pango_style(face->style_flags));