analysis

func AlignmentCheck ¶

func AlignmentCheck(t *testing.T, typ reflect.Type) (ok bool, delta uint64)

AlignmentCheck ensures the definition of the type represented by typ doesn't cause the go compiler to emit implicit padding between elements of the type (i.e. fields in a struct).

AlignmentCheck doesn't explicitly recurse for embedded structs because any struct present in an ABI struct must also be Marshallable, and therefore they're aligned by definition (or their alignment check would have failed).

func RandomizeValue ¶

func RandomizeValue(x any)

RandomizeValue assigns random value(s) to an abitrary type. This is intended for used with ABI structs from go_marshal, meaning the typical restrictions apply (fixed-size types, no pointers, maps, channels, etc), and should only be used on zeroed values to avoid overwriting pointers to active go objects.

Internally, we populate the type with random data by doing an unsafe cast to access the underlying memory of the type and filling it as if it were a byte slice. This almost gets us what we want, but padding fields named "_" are normally not accessible, so we walk the type and recursively zero all "_" fields.

Precondition: x must be a pointer. x must not contain any valid pointers to active go objects (pointer fields aren't allowed in ABI structs anyways), or we'd be violating the go runtime contract and the GC may malfunction.