Signature Validity Rules

Let’s wrap up the basic facts discussed in this chapter:

• [run time] Signature entries of records in the Method, Field, Property, MemberRef, StandaloneSig, and TypeSpec metadata tables must hold valid offsets in the #Blob stream. Nil values of these entries are not acceptable.

• Signatures are built from SETs. Each SET describes the type of a field, a parameter, or other such item.

• [run time] Each SET is a sequence of primitive type codes and optional integer parameters, such as metadata tokens or array dimension sizes. A SET cannot end with the following primitive types: a sentinel, * , & , [ ] , or pinned . These primitive types are modifiers for the types that follow them in the SET.

• [run time] A field signature, which is referenced from the Field or MemberRef table, consists of the calling convention IMAGE_CEE_CS _CALLCONV_FIELD and one valid SET, which cannot be void or <type> & and cannot contain a sentinel or a pinned modifier.

• A method reference signature, which is referenced from the MemberRef table, consists of a calling convention, an argument count, a return SET, and a sequence of argument SETs, corresponding in number to the argument count.

• [run time] The calling convention of a method reference signature is one of the following: the default, vararg , instance , instance vararg , instance explicit , or instance explicit vararg.

• [run time] The return SET of a method reference signature cannot contain a sentinel or a pinned modifier.

• [run time] No more than one argument SET of a method reference signature can contain a sentinel, and it can do so only if the calling convention includes vararg .

• [run time] The argument SETs of a method reference signature cannot be void and cannot contain a pinned modifier.

• A method declaration signature, which is referenced from the Method table, has the same structure as a method reference signature and must comply with the same requirements, plus the following restrictions: the explicit calling convention cannot be used, and no argument SET can contain a sentinel.

• A property declaration signature, which is referenced from the Property table, has the same structure as a method declaration signature and must comply with the same requirements except that the calling convention of a property declaration signature must be IMAGE_CEE_CS_CALLCONV_PROPERTY .

• An indirect call signature, which is referenced from the StandAloneSig table, has the same structure as a method reference signature and must comply with the same requirements except that the calling convention of an indirect call to an unmanaged method can be unmanaged cdecl , unmanaged stdcall , unmanaged thiscall , or unmanaged fastcall .

• A local variables signature, which is referenced from the StandAloneSig table, consists of the calling convention IMAGE_CEE_CS_CALL- CONV_LOCAL_SIG , a local variable count, and a sequence of variable SETs, corresponding in number to the variable count.

• [run time] No variable SET can be void or can contain a sentinel.

• A type specification signature, which is referenced from the TypeSpec table, consists of one SET not preceded by the calling convention. The SET must represent an array, a vector, an unmanaged pointer, or a function pointer, and it cannot contain a pinned modifier.