_generic_matmatmul! calls conj! on potentially uninitialized arrays

[fkastner]

Hi,

in _generic_matmatmul! there is a call to copyto! (Ref.):

copyto!(Btile, 1:mB, 1:nB, tB, B, 1:mB, 1:nB)

in which (Ref.)Btile will only be initialized in the range (1:mB, 1:nB) which is smaller than size(Btile). Afterwards conj!(Btile) is called which now also tries to conjugate also the uninitialized entries outside (1:mB, 1:nB).

This leads to problems with custom types since the uninitialized memory does not necessarily represent a valid object and conj could fail on invalid objects that violate certain assumptions.

Possibly conj! should only be called on B[1:mB, 1:nB]?

[fkastner]

Fixed by JuliaLang/julia#40481.