[llvm] r296891 - Don't bring in llvm/Support/thread.h in Threading.cpp

[Zachary Turner via llvm-commits]

Author: zturner
Date: Fri Mar  3 11:39:24 2017
New Revision: 296891

URL: http://llvm.org/viewvc/llvm-project?rev=296891&view=rev
Log:
Don't bring in llvm/Support/thread.h in Threading.cpp

Doing so defines the type llvm::thread.  On FreeBSD, we need
to call a macro which references its own ::thread type, which
causes an ambiguity due to ADL when inside of the llvm namespace.

Since we don't even need this unless LLVM_ENABLE_THREADS == 1,
we don't even need this type anyway, as it is always equal to
std::thread, so we can just use that directly.

Modified:
    llvm/trunk/lib/Support/Threading.cpp

Modified: llvm/trunk/lib/Support/Threading.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Threading.cpp?rev=296891&r1=296890&r2=296891&view=diff
==============================================================================
--- llvm/trunk/lib/Support/Threading.cpp (original)
+++ llvm/trunk/lib/Support/Threading.cpp Fri Mar  3 11:39:24 2017
@@ -15,7 +15,6 @@
 #include "llvm/Support/Threading.h"
 #include "llvm/Config/config.h"
 #include "llvm/Support/Host.h"
-#include "llvm/Support/thread.h"
 
 #include <cassert>
 #include <errno.h>
@@ -56,10 +55,17 @@ void llvm::get_thread_name(SmallVectorIm
 
 #else
 
+#include <thread>
 unsigned llvm::heavyweight_hardware_concurrency() {
+  // Since we can't get here unless LLVM_ENABLE_THREADS == 1, it is safe to use
+  // `std::thread` directly instead of `llvm::thread` (and indeed, doing so
+  // allows us to not define `thread` in the llvm namespace, which conflicts
+  // with some platforms such as FreeBSD whose headers also define a struct
+  // called `thread` in the global namespace which can cause ambiguity due to
+  // ADL.
   int NumPhysical = sys::getHostNumPhysicalCores();
   if (NumPhysical == -1)
-    return thread::hardware_concurrency();
+    return std::thread::hardware_concurrency();
   return NumPhysical;
 }