Metadata Validity Rules | Inside Microsoft .NET IL Assembler

Metadata Validity Rules

The field-related metadata tables include the Field, FieldLayout, FieldRVA, FieldMarshal, Constant, and MemberRef tables. The records of these tables have the following entries:

The Field table contains the Flags, Name, and Signature entries.
The FieldLayout table contains the OffSet and Field entries.
The FieldRVA table contains the RVA and Field entries.
The FieldMarshal table contains the Parent and NativeType (native signature) entries.
The Constant table contains the Type, Parent, and Value entries.
The MemberRef table contains the Class, Name, and Signature entries.

Field Table Validity Rules

The Flags entry can have only those bits set that are defined in the enumeration CorFieldAttrEnum in CorHdr.h (validity mask: 0xB7F7).
[run time] The accessibility flag (mask 0x0007) must be one of the following: privatescope, private, famandassem, assembly, family, famorassem, or public.
The literal and initonly flags are mutually exclusive.
If the literal flag is set, the static flag must also be set.
If the rtspecialname flag is set, the specialname flag must also be set.
[run time] If the flag 0x1000 (fdHasFieldMarshal) is set, the FieldMarshal table must contain a record referencing this Field record, and vice versa.
[run time] If the flag 0x8000 (fdHasDefault) is set, the Constant table must contain a record referencing this Field record, and vice versa.
[run time] If the flag 0x0100 (fdHasFieldRVA) is set, the FieldRVA table must contain a record referencing this Field record, and vice versa.
[run time] Global fields, owned by the TypeDef <Module>, must have the static flag set.
[run time] The Name entry must hold a valid reference to the #Strings stream, indexing a nonempty string no more than 1023 bytes long in UTF-8 encoding.
[run time] The Signature entry must hold a valid reference to the #Blob stream, indexing a valid field signature. Validity rules for field signatures are discussed in Chapter 7.
No duplicate records—attributed to the same TypeDef and having the same Name and Signature values—can exist unless the accessibility flag is privatescope.
Fields attributed to enumerators must comply with additional rules, described in Chapter 6.

FieldLayout Table Validity Rules

The Field entry must hold a valid reference to the Field table.
The field referenced in the Field entry must not have the static flag set.
[run time] If the referenced field is an object reference type and belongs to TypeDefs that have an explicit layout, the OffSet entry must hold a value that is a multiple of sizeof(void*).
[run time] If the referenced field is an object reference type and belongs to TypeDefs that have an explicit layout, this field must not overlap with any other field.

FieldRVA Table Validity Rules

[run time] The RVA entry must hold a valid nonzero relative virtual address.
The Field entry must hold a valid index to the Field table.
No duplicate records referencing the same field can exist.

FieldMarshal Table Validity Rules

The Parent entry must hold a valid reference to the Field or Param table.
No duplicate records that contain the same Parent value can exist.
The NativeType entry must hold a valid reference to the #Blob stream, indexing a valid marshaling signature. Native types that make up the marshaling signatures are described in Chapter 7.

Constant Table Validity Rules

The Type entry must hold a valid ELEMENT_TYPE_* code, one of the following: bool, char, a signed or unsigned integer of 1 to 8 bytes, string, or object.
The Value entry must hold a valid offset in the #Blob stream.
The Parent entry must hold a valid reference to the Field, Property, or Param table.
No duplicate records that contain the same Parent value can exist.

MemberRef Table Validity Rules

[run time] The Class entry must hold a valid reference to one of the following tables: TypeRef, TypeSpec, ModuleRef, MemberRef, or Method.
[run time] The Class entry of a MemberRef record referencing a field must hold a valid reference to the TypeRef or ModuleRef table.
[run time] The Name entry must hold a valid offset in the #Strings stream, indexing a nonempty string no longer than 1023 bytes in UTF-8 encoding.
[run time] The name defined by the Name entry must not match the common language runtime reserved names _Deleted* or _VtblGap*.
[run time] The Signature entry must hold a valid offset in the #Blob stream, indexing a valid MemberRef signature. Validity rules for MemberRef signatures are discussed in Chapter 7.
No duplicate records with all three entries matching can exist.
An item (field or method) that a MemberRef record references must not have the accessibility flag privatescope.