From 14d6470ad36a1682966ff93e774849901055a916 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Wed, 2 Dec 2015 13:38:59 +0100
Subject: prefer pthread-semaphores (posix API) with mingw

Hopefully this resolves glitches on hyperthreading machines.
Apart from using unnamed Semaphores, pthread-w32 includes additional locks
(guess: mem-barriers), a fallback implementation and windows-specific
tricks that I'd rather not want to know about :)
---
 libs/pbd/pbd/semutils.h | 11 ++++++++---
 libs/pbd/semutils.cc    |  6 +++---
 wscript                 |  8 +++++++-
 3 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/libs/pbd/pbd/semutils.h b/libs/pbd/pbd/semutils.h
index 5c0191e25b..50ac41919c 100644
--- a/libs/pbd/pbd/semutils.h
+++ b/libs/pbd/pbd/semutils.h
@@ -19,9 +19,14 @@
 #ifndef __pbd_semutils_h__
 #define __pbd_semutils_h__
 
-#ifdef PLATFORM_WINDOWS
+#if (defined PLATFORM_WINDOWS && !defined USE_PTW32_SEMAPHORE)
+#define WINDOWS_SEMAPHORE 1
+#endif
+
+#ifdef WINDOWS_SEMAPHORE
 #include <windows.h>
 #else
+#include <pthread.h>
 #include <semaphore.h>
 #endif
 
@@ -31,7 +36,7 @@ namespace PBD {
 
 class LIBPBD_API ProcessSemaphore {
   private:
-#ifdef PLATFORM_WINDOWS
+#ifdef WINDOWS_SEMAPHORE
 	HANDLE _sem;
 
 #elif __APPLE__
@@ -46,7 +51,7 @@ class LIBPBD_API ProcessSemaphore {
 	ProcessSemaphore (const char* name, int val);
 	~ProcessSemaphore ();
 
-#ifdef PLATFORM_WINDOWS
+#ifdef WINDOWS_SEMAPHORE
 
 	int signal ();
 	int wait ();
diff --git a/libs/pbd/semutils.cc b/libs/pbd/semutils.cc
index 5d3ef3d958..bafa447f8f 100644
--- a/libs/pbd/semutils.cc
+++ b/libs/pbd/semutils.cc
@@ -23,7 +23,7 @@ using namespace PBD;
 
 ProcessSemaphore::ProcessSemaphore (const char* name, int val)
 {
-#ifdef PLATFORM_WINDOWS
+#ifdef WINDOWS_SEMAPHORE
 	if ((_sem = CreateSemaphore(NULL, val, 32767, name)) == NULL) {
 		throw failed_constructor ();
 	}
@@ -50,14 +50,14 @@ ProcessSemaphore::ProcessSemaphore (const char* name, int val)
 
 ProcessSemaphore::~ProcessSemaphore ()
 {
-#ifdef PLATFORM_WINDOWS
+#ifdef WINDOWS_SEMAPHORE
 	CloseHandle(_sem);
 #elif __APPLE__
 	sem_close (ptr_to_sem());
 #endif
 }
 
-#ifdef PLATFORM_WINDOWS
+#ifdef WINDOWS_SEMAPHORE
 
 int
 ProcessSemaphore::signal ()
diff --git a/wscript b/wscript
index cefe9998d9..041b12ecba 100644
--- a/wscript
+++ b/wscript
@@ -963,6 +963,11 @@ int main () { int x = SFC_RF64_AUTO_DOWNGRADE; return 0; }
         conf.env.append_value('CXXFLAGS', '-DUSE_CAIRO_IMAGE_SURFACE')
         conf.define ('WINDOWS', 1)
 
+        if os.path.isfile (user_gtk_root + 'include/semaphore.h'):
+            conf.define ('USE_PTW32_SEMAPHORE', 1)
+            conf.env.append_value('CFLAGS', '-DUSE_PTW32_SEMAPHORE')
+            conf.env.append_value('CXXFLAGS', '-DUSE_PTW32_SEMAPHORE')
+
     if Options.options.dist_target == 'msvc':
         conf.env.append_value('CFLAGS', '-DPLATFORM_WINDOWS')
         conf.env.append_value('CFLAGS', '-DCOMPILER_MSVC')
@@ -1144,7 +1149,8 @@ const char* const ardour_config_info = "\\n\\
     write_config_text('Phone home',            conf.is_defined('PHONE_HOME'))
     write_config_text('Program name',          opts.program_name)
     write_config_text('Samplerate',            conf.is_defined('HAVE_SAMPLERATE'))
-    write_config_text('PT format',            conf.is_defined('PTFORMAT'))
+    write_config_text('PT format',             conf.is_defined('PTFORMAT'))
+    write_config_text('PTW32 Semaphore',       conf.is_defined('USE_PTW32_SEMAPHORE'))
 #    write_config_text('Soundtouch',            conf.is_defined('HAVE_SOUNDTOUCH'))
     write_config_text('Translation',           opts.nls)
 #    write_config_text('Tranzport',             opts.tranzport)
-- 
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