[PATCH] D28220: provide Win32 native threading

[Eric Fiselier via Phabricator via cfe-commits]

EricWF added inline comments.


================
Comment at: include/__threading_support:30
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#include <process.h>
----------------
EricWF wrote:
> smeenai wrote:
> > EricWF wrote:
> > > EricWF wrote:
> > > > smeenai wrote:
> > > > > EricWF wrote:
> > > > > > > Can we do as Reid suggests and not expose users to windows.h?
> > > > > > 
> > > > > > I was about to ask the same question.  These includes are dragging in the `__deallocate` macro and I would love to avoid that.
> > > > > I feel like we would end up with a //lot// of duplication if we went down this route, since this is using a fair amount of Windows APIs. @rnk suggested having a test for prototype mismatches, but even with those checks there could be a high maintenance burden to the duplication.
> > > > > 
> > > > > Was the main objection to `WIN32_LEAN_AND_MEAN` that it would be problematic for modules? If we're including `windows.h`, it seems strictly preferable to include it with `WIN32_LEAN_AND_MEAN` than without, since we'll pull in a lot less that way. Including `windows.h` without `WIN32_LEAN_AND_MEAN` can also interact with other headers badly sometimes, e.g. [`winsock2.h`](https://msdn.microsoft.com/en-us/library/windows/desktop/ms737629%28v=vs.85%29.aspx).
> > > > It seems that dragging in the `__deallocate` macro is inevitable :-( 
> > > > 
> > > > I submitted a patch to work around `__deallocate` here: https://reviews.llvm.org/D28426
> > > > Was the main objection to WIN32_LEAN_AND_MEAN that it would be problematic for modules? If we're including windows.h, it seems strictly preferable to include it with WIN32_LEAN_AND_MEAN than without, since we'll pull in a lot less that way. Including windows.h without WIN32_LEAN_AND_MEAN can also interact with other headers badly sometimes, e.g. winsock2.h.
> > > 
> > > The objection is that it breaks user code. For example:
> > > 
> > > ```
> > > #include <thread>
> > > #include <Windows.h> // Windows.h already included as lean and mean.
> > > 
> > > typedef NonLeanAndMeanSymbol foo; // ERROR NonLeanAndMeanSymbol not defined
> > > 
> > > ```
> > > 
> > But without the `WIN32_LEAN_AND_MEAN`, we're gonna break
> > 
> > ```
> > #include <thread>
> > #include <winsock2.h>
> > ```
> > 
> > (you could fix this by reordering the includes, which would also fix your example, or by defining `WIN32_LEAN_AND_MEAN` yourself, but it doesn't seem great either)
> I would much rather break that code. The fact that `Windows.h` doesn't play nice with other Windows headers is a problem for Windows not libc++.
Although I think avoiding the `Windows.h` include all together would be better (if possible). However I think that can be fixed after committing this.


https://reviews.llvm.org/D28220