[vala/staging] codegen: Check vfunc of abstract/virtual methods for NULL before using it

[Rico Tzschichholz <ricotz src gnome org>]

commit 7c6e7e64bbde1af258634aca28014286682c42cc
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Wed Apr 15 16:24:10 2020 +0200

    codegen: Check vfunc of abstract/virtual methods for NULL before using it
    
    Fixes https://gitlab.gnome.org/GNOME/vala/issues/153

 codegen/valaccodemethodmodule.vala | 39 +++++++++++++++++++++++++++++++-------
 1 file changed, 32 insertions(+), 7 deletions(-)
---
diff --git a/codegen/valaccodemethodmodule.vala b/codegen/valaccodemethodmodule.vala
index 03b382ac4..b90ebf4fa 100644
--- a/codegen/valaccodemethodmodule.vala
+++ b/codegen/valaccodemethodmodule.vala
@@ -1068,15 +1068,11 @@ public abstract class Vala.CCodeMethodModule : CCodeStructModule {
 
                CCodeExpression vcast;
                if (m.parent_symbol is Interface) {
-                       var iface = (Interface) m.parent_symbol;
-
-                       vcast = new CCodeFunctionCall (new CCodeIdentifier (get_ccode_interface_get_function 
(iface)));
-                       ((CCodeFunctionCall) vcast).add_argument (new CCodeIdentifier ("self"));
+                       vcast = new CCodeIdentifier ("iface");
                } else {
                        var cl = (Class) m.parent_symbol;
                        if (!cl.is_compact) {
-                               vcast = new CCodeFunctionCall (new CCodeIdentifier 
(get_ccode_class_get_function (cl)));
-                               ((CCodeFunctionCall) vcast).add_argument (new CCodeIdentifier ("self"));
+                               vcast = new CCodeIdentifier ("klass");
                        } else {
                                vcast = new CCodeIdentifier ("self");
                        }
@@ -1095,7 +1091,7 @@ public abstract class Vala.CCodeMethodModule : CCodeStructModule {
 
                push_function (vfunc);
 
-               if (context.assert && m.return_type.type_symbol is Struct && ((Struct) 
m.return_type.type_symbol).is_simple_type () && default_value_for_type (m.return_type, false) == null) {
+               if (m.return_type.is_non_null_simple_type () && default_value_for_type (m.return_type, false) 
== null) {
                        // the type check will use the result variable
                        var vardecl = new CCodeVariableDeclarator ("result", default_value_for_type 
(m.return_type, true));
                        vardecl.init0 = true;
@@ -1109,6 +1105,27 @@ public abstract class Vala.CCodeMethodModule : CCodeStructModule {
                        create_precondition_statement (m, return_type, precondition);
                }
 
+               if (m.parent_symbol is Interface) {
+                       var iface = (Interface) m.parent_symbol;
+
+                       var vcastcall = new CCodeFunctionCall (new CCodeIdentifier 
(get_ccode_interface_get_function (iface)));
+                       ((CCodeFunctionCall) vcastcall).add_argument (new CCodeIdentifier ("self"));
+                       ccode.add_declaration ("%s*".printf (get_ccode_type_name (iface)), new 
CCodeVariableDeclarator ("iface"));
+                       ccode.add_assignment (vcast, vcastcall);
+               } else {
+                       var cl = (Class) m.parent_symbol;
+                       if (!cl.is_compact) {
+                               var vcastcall = new CCodeFunctionCall (new CCodeIdentifier 
(get_ccode_class_get_function (cl)));
+                               ((CCodeFunctionCall) vcastcall).add_argument (new CCodeIdentifier ("self"));
+                               vcast = new CCodeIdentifier ("klass");
+                               ccode.add_declaration ("%sClass*".printf (get_ccode_name (cl)), new 
CCodeVariableDeclarator ("klass"));
+                               ccode.add_assignment (vcast, vcastcall);
+                       }
+               }
+
+               // check if vfunc pointer is properly set
+               ccode.open_if (vcall.call);
+
                if (return_type is VoidType || return_type.is_real_non_null_struct_type ()) {
                        ccode.add_expression (vcall);
                } else if (m.get_postconditions ().size == 0) {
@@ -1130,6 +1147,14 @@ public abstract class Vala.CCodeMethodModule : CCodeStructModule {
                        }
                }
 
+               ccode.close ();
+
+               if (m.return_type.is_non_null_simple_type () && default_value_for_type (m.return_type, false) 
== null) {
+                       ccode.add_return (new CCodeIdentifier ("result"));
+               } else if (!(return_type is VoidType)) {
+                       ccode.add_return (default_value_for_type (return_type, false, true));
+               }
+
                if (m.printf_format) {
                        vfunc.modifiers |= CCodeModifiers.PRINTF;
                } else if (m.scanf_format) {