Bug: IStream_Vtbl's Seek wrapper can dereference null pointer

[miolad]

The implementation of the wrapper of IStream::Seek doesn't check whether plibNewPosition is NULL before writing to it, even though the docs state that NULL is indeed a valid value for that parameter.

windows-rs/crates/libs/windows/src/Windows/Win32/System/Com/impl.rs

Line 3804 in 4726348

::core::ptr::write(plibnewposition, ::core::mem::transmute(ok__));

[kennykerr]

Implementation support still needs some work. You can use the interface macro as a workaround in the meantime.

[kennykerr]

Tracked this down and it's rooted in a Win32 metadata bug: microsoft/win32metadata#1005

The challenge is that this parameter is a trailing optional parameter and many such parameters are incorrectly marked as optional in metadata. Anyway, I've got a fix for this issue and hopefully the metadata will be improved shortly.

[kennykerr]

This line:

windows-rs/crates/libs/metadata/src/reader/mod.rs

Line 1336 in eb9d65c

if flags.input() || !flags.output() || param.kind.is_array() {

Needs to include optional parameters as follows:

if flags.input() || !flags.output() || flags.optional() || param.kind.is_array() {

But that's blocked on: microsoft/win32metadata#1005