iii.3.45-ldnull.md

III.3.45 ldnull – load a null pointer

Format	Assembly Format	Description
14	ldnull	Push a null reference on the stack.

Stack Transition:

… → …, null value

Description:

The ldnull pushes a null reference (type O) on the stack. This is used to initialize locations before they become live or when they become dead.

[Rationale: It might be thought that ldnull is redundant: why not use ldc.i4.0 or ldc.i8.0 instead? The answer is that ldnull provides a size-agnostic null – analogous to an ldc.i instruction, which does not exist. However, even if CIL were to include an ldc.i instruction it would still benefit verification algorithms to retain the ldnull instruction because it makes type tracking easier. end rationale]

Exceptions:

None.

Correctness:

Verifiability:

The ldnull instruction is always verifiable, and produces a value of the null type (§III.1.8.1.2) that is assignable-to (§I.8.7.3) any other reference type.