On 19/01/2021 14:04, Rémi Bernon wrote:

diff --git a/tools/widl/parser.l b/tools/widl/parser.l
index 01c6f800a08..067966a85d4 100644
--- a/tools/widl/parser.l
+++ b/tools/widl/parser.l
@@ -385,6 +385,7 @@ static const struct keyword attr_keywords[] =
  	{"marshaling_behavior",         tMARSHALINGBEHAVIOR,        1},
  	{"maybe",                       tMAYBE,                     0},
  	{"message",                     tMESSAGE,                   0},
+	{"mta" ,                        tMTA,                       1},
  	{"neutral",                     tNEUTRAL,                   0},
  	{"nocode",                      tNOCODE,                    0},
  	{"nonbrowsable",                tNONBROWSABLE,              0},

I think that currently threading attribute is used only as widl
extension for registration code. It probably predates midl winrt, but
it looks like it's mostly compatible. Maybe we should make the
extension more compatible with winrt, eg. migrate our code to use
'mta' instead or 'free' (instead of making mta winrt-only)?

The current support was modeled after the C++ attributes:

  https://docs.microsoft.com/en-us/cpp/windows/attributes/threading-cpp?view=msvc-160

so it may make sense to keep 'free' as an alias. OTOH we don't seem to
be using it in the existing code anyway.

Sure, but even if we keep the alias, it seems right to always expose 'mta' together with threading attribute rather than having it winrt-only.

Jacek