[Mono-bugs] [Bug 75479][Nor] Changed - mono_class_from_mono_type()/mono_type_get_underlying_type() and generics

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Changed by lupus at ximian.com.

http://bugzilla.ximian.com/show_bug.cgi?id=75479

--- shadow/75479	2005-12-08 13:35:30.000000000 -0500
+++ shadow/75479.tmp.3362	2006-02-14 08:27:22.000000000 -0500
@@ -4,20 +4,19 @@
 OS: unknown
 OS Details: amd64 pld linux
 Status: NEW   
 Resolution: 
 Severity: Unknown
 Priority: Normal
-Component: GC
+Component: misc
 AssignedTo: lupus at ximian.com                            
 ReportedBy: malekith at pld-linux.org               
 QAContact: mono-bugs at ximian.com
 TargetMilestone: ---
 URL: 
-Cc: 
-Summary: [GMCS] GC is confused by generic structs
+Summary: mono_class_from_mono_type()/mono_type_get_underlying_type() and generics
 
 Description of Problem:
 
 The following testcase:
 
 #v+
@@ -242,6 +241,32 @@
 ------- Additional Comments From martin at ximian.com  2005-12-08 13:35 -------
 Thanks a lot for wasting yet another afternoon on this.  I checked
 get_underlying_type() everywhere and it's correct everywhere. 
 Considering the amout on time already spent on this bug (3.5 days), I
 have no other choice but close it as WONTFIX if it ever bounces back
 to me.
+
+------- Additional Comments From lupus at ximian.com  2006-02-14 08:27 -------
+The issue exposed by the test case can be 'fixed' with this temporary
+patch:
+--- metadata/class.c	(revision 56832)
++++ metadata/class.c	(working copy)
+@@ -983,7 +984,7 @@
+ 
+ 		if (!(field->type->attrs & FIELD_ATTRIBUTE_STATIC)) {
+ 			ftype = mono_type_get_underlying_type (field->type);
+-			if (MONO_TYPE_IS_REFERENCE (ftype) || IS_GC_REFERENCE (ftype) ||
+((MONO_TYPE_ISSTRUCT (ftype) && mono_class_has_references
+(mono_class_from_mono_type (ftype)))))
++			if (MONO_TYPE_IS_REFERENCE (ftype) || IS_GC_REFERENCE (ftype) ||
+((MONO_TYPE_ISSTRUCT (ftype) && mono_class_has_references
+(mono_class_from_mono_type (field->type)))))
+ 				class->has_references = TRUE;
+ 		}
+ 	}
+
+The problem here is that mono_type_get_underlying_type() will return
+a broken type pointer, at least in the case of an instantiated generic
+struct. The low-level type is MONO_TYPE_VALUETYPE, but the MonoClass*
+pointer in it points to the uninstantiated generic struct and not the
+correct instantiated one, so when mono_class_from_mono_type() is
+called on it it gets the wrong info.