public override ComputedInstanceFieldLayout ComputeInstanceLayout(DefType defType, InstanceLayoutKind layoutKind)
{
MetadataType type = (MetadataType)defType;
if (type.IsGenericDefinition)
{
ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadGeneral, type);
}
// CLI - Partition 1, section 9.5 - Generic types shall not be marked explicitlayout.
if (type.HasInstantiation && type.IsExplicitLayout)
{
ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadExplicitGeneric, type.GetTypeDefinition());
}
// Count the number of instance fields in advance for convenience
int numInstanceFields = 0;
foreach (var field in type.GetFields())
{
if (field.IsStatic)
{
continue;
}
TypeDesc fieldType = field.FieldType;
// ByRef instance fields are not allowed.
if (fieldType.IsByRef)
{
ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadGeneral, type);
}
// ByRef-like instance fields on non-byref-like types are not allowed.
if (fieldType.IsByRefLike && !type.IsByRefLike)
{
ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadGeneral, type);
}
numInstanceFields++;
}
if (type.IsModuleType)
{
// This is a global type, it must not have instance fields.
if (numInstanceFields > 0)
{
ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadGeneral, type);
}
// Global types do not do the rest of instance field layout.
ComputedInstanceFieldLayout result = new ComputedInstanceFieldLayout();
result.Offsets = Array.Empty <FieldAndOffset>();
return(result);
}
// CLI - Partition 2, section 22.8
// A type has layout if it is marked SequentialLayout or ExplicitLayout. If any type within an inheritance chain has layout,
// then so shall all its base classes, up to the one that descends immediately from System.ValueType (if it exists in the type's
// hierarchy); otherwise, from System.Object
// Note: While the CLI isn't clearly worded, the layout needs to be the same for the entire chain.
// If the current type isn't ValueType or System.Object and has a layout and the parent type isn't
// ValueType or System.Object then the layout type attributes need to match
if ((!type.IsValueType && !type.IsObject) &&
(type.IsSequentialLayout || type.IsExplicitLayout) &&
(!type.BaseType.IsValueType && !type.BaseType.IsObject))
{
MetadataType baseType = type.MetadataBaseType;
if (type.IsSequentialLayout != baseType.IsSequentialLayout ||
type.IsExplicitLayout != baseType.IsExplicitLayout)
{
ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadBadFormat, type);
}
}
// Enum types must have a single instance field
if (type.IsEnum && numInstanceFields != 1)
{
ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadGeneral, type);
}
if (type.IsPrimitive)
{
// Primitive types are special - they may have a single field of the same type
// as the type itself. They do not do the rest of instance field layout.
if (numInstanceFields > 1)
{
ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadGeneral, type);
}
SizeAndAlignment instanceByteSizeAndAlignment;
var sizeAndAlignment = ComputeInstanceSize(
type,
type.Context.Target.GetWellKnownTypeSize(type),
type.Context.Target.GetWellKnownTypeAlignment(type),
0,
out instanceByteSizeAndAlignment
);
ComputedInstanceFieldLayout result = new ComputedInstanceFieldLayout
{
ByteCountUnaligned = instanceByteSizeAndAlignment.Size,
ByteCountAlignment = instanceByteSizeAndAlignment.Alignment,
FieldAlignment = sizeAndAlignment.Alignment,
FieldSize = sizeAndAlignment.Size,
};
if (numInstanceFields > 0)
{
FieldDesc instanceField = null;
foreach (FieldDesc field in type.GetFields())
{
if (!field.IsStatic)
{
Debug.Assert(instanceField == null, "Unexpected extra instance field");
instanceField = field;
}
}
Debug.Assert(instanceField != null, "Null instance field");
result.Offsets = new FieldAndOffset[] {
new FieldAndOffset(instanceField, LayoutInt.Zero)
};
}
else
{
result.Offsets = Array.Empty <FieldAndOffset>();
}
return(result);
}
// If the type has layout, read its packing and size info
// If the type has explicit layout, also read the field offset info
if (type.IsExplicitLayout || type.IsSequentialLayout)
{
if (type.IsEnum)
{
ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadBadFormat, type);
}
var layoutMetadata = type.GetClassLayout();
// If packing is out of range or not a power of two, throw that the size is invalid
int packing = layoutMetadata.PackingSize;
if (packing < 0 || packing > 128 || ((packing & (packing - 1)) != 0))
{
ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadBadFormat, type);
}
Debug.Assert(layoutMetadata.Offsets == null || layoutMetadata.Offsets.Length == numInstanceFields);
}
// At this point all special cases are handled and all inputs validated
return(ComputeInstanceFieldLayout(type, numInstanceFields));
}