Question

/clr:pure switch generates pure MSIL but it is not verifible. Native array and pointer can be used in this mode. Does that mean that there is a structure in MSIL to hold native arrays and pointers? If yes, I would like to ask how can I code MSIL native array and pointer?

Answer 1

Yes, there is a type in CIL to represent unmanaged pointers. They are similar to managed pointers (ref and out in C#, & in CIL), except that GC ignores them and you can do some arithmetic operations on them (those that make sense with pointers).

Interestingly, the pointer type does contain information about the target type (so it’s e.g. int32*), but all arithmetic operations are byte based.

As an example, the following C++/CLI method:

void Bar(int *a)
{
    a[5] = 15;
}

produces the following CIL when it’s inside a ref class (as reported by Reflector):

.method private hidebysig instance void Bar(int32* a) cil managed
{
    .maxstack 2
    L_0000: ldarg.1      // load the value of a pointer to the stack
    L_0001: ldc.i4.s 20  // load the number 20 (= 4 * 5) to the stack
    L_0003: add          // add 20 to the pointer
    L_0004: ldc.i4.s 15  // load the number 15 to the stack
    L_0006: stind.i4     // store the value of 15 at the computed address
    L_0007: ret          // return from the method
}