Follow up d8ae3fd

Depending on implementation, d8ae3fd may only construct the spinlock
once to `sl_init`. Later it is only copy-constructed and that leads to
compile and/or runtmime errors.

e.g. gcc-8.3 fails to compile
error: use of deleted function ‘boost::detail::spinlock::spinlock(const boost::detail::spinlock&)’

diff --git a/libs/pbd/pbd/spinlock.h b/libs/pbd/pbd/spinlock.h
index 7173fde594d176d733653666ec280ed36180cd67..69b76ce820d7b58dcf750cd6a8b6116e8f69c462 100644 (file)
--- a/libs/pbd/pbd/spinlock.h
+++ b/libs/pbd/pbd/spinlock.h
@@ -32,11 +32,17 @@ namespace PBD {
  *
  * initialize with BOOST_DETAIL_SPINLOCK_INIT
  */
-static boost::detail::spinlock sl_init = BOOST_DETAIL_SPINLOCK_INIT;
+#ifdef COMPILER_MSVC
+private:
+       static boost::detail::spinlock sl_init = BOOST_DETAIL_SPINLOCK_INIT;
+# define SPINLOCK_INIT sl_init
+#else
+# define SPINLOCK_INIT BOOST_DETAIL_SPINLOCK_INIT
+#endif
 
 struct spinlock_t {
 public:
-       spinlock_t () : l (sl_init) {};
+       spinlock_t () : l (SPINLOCK_INIT) {};
        void lock () { l.lock (); }
        void unlock () { l.unlock (); }
        bool try_lock () { return l.try_lock (); }
@@ -44,6 +50,8 @@ private:
        boost::detail::spinlock l;
 };
 
+#undef SPINLOCK_INIT
+
 /* RAII wrapper */
 class LIBPBD_API SpinLock {