Add low-level once API that is static initialization-safe

5 files changed, 39 insertions, 21 deletions

diff --git a/odb/details/win32/once.cxx b/odb/details/win32/once.cxx
index 0125d23..33523c3 100644
--- a/odb/details/win32/once.cxx
+++ b/odb/details/win32/once.cxx
@@ -16,18 +16,18 @@ namespace odb
 {
   namespace details
   {
-    CRITICAL_SECTION once::cs_;
+    CRITICAL_SECTION win32_once_cs_;
 
     void
     once_process_start ()
     {
-      InitializeCriticalSection (&once::cs_);
+      InitializeCriticalSection (&win32_once_cs_);
     }
 
     void
     once_process_end (bool)
     {
-      DeleteCriticalSection (&once::cs_);
+      DeleteCriticalSection (&win32_once_cs_);
     }
   }
 }
diff --git a/odb/details/win32/once.hxx b/odb/details/win32/once.hxx
index 05bdca2..c6c31f6 100644
--- a/odb/details/win32/once.hxx
+++ b/odb/details/win32/once.hxx
@@ -35,16 +35,20 @@ namespace odb
       once& operator= (const once&);
 
     private:
-      friend void
-      once_process_start ();
-
-      friend void
-      once_process_end (bool);
-
-    private:
       bool called_;
-      static CRITICAL_SECTION cs_;
     };
+
+    // Low-level, POSIX-like API that can be used safely during static
+    // initialization (that is, win32_once() can be called during static
+    // initialization) provided once_process_start() has been called.
+    //
+    typedef unsigned int win32_once_t;
+    const win32_once_t WIN32_ONCE_INIT = 0;
+
+    LIBODB_EXPORT void
+    win32_once (win32_once_t&, void (*func) ());
+
+    extern LIBODB_EXPORT CRITICAL_SECTION win32_once_cs_;
   }
 }
 
diff --git a/odb/details/win32/once.ixx b/odb/details/win32/once.ixx
index 9f1706d..de46371 100644
--- a/odb/details/win32/once.ixx
+++ b/odb/details/win32/once.ixx
@@ -9,6 +9,19 @@ namespace odb
 {
   namespace details
   {
+    inline void
+    win32_once (win32_once_t& o, void (*func) ())
+    {
+      win32_lock l (win32_once_cs_);
+
+      if (o == 0)
+      {
+        o = 1;
+        l.unlock ();
+        func ();
+      }
+    }
+
     inline once::
     once ()
         : called_ (false)
@@ -18,12 +31,13 @@ namespace odb
     inline void once::
     call (void (*func) ())
     {
-      win32_lock l (cs_);
+      win32_lock l (win32_once_cs_);
 
       if (!called_)
       {
-        func ();
         called_ = true;
+        l.unlock ();
+        func ();
       }
     }
   }
diff --git a/odb/details/win32/tls.hxx b/odb/details/win32/tls.hxx
index 3354723..3dcb571 100644
--- a/odb/details/win32/tls.hxx
+++ b/odb/details/win32/tls.hxx
@@ -54,7 +54,7 @@ namespace odb
       destructor (void*);
 
     private:
-      static once once_;
+      static win32_once_t once_;
       static std::size_t key_;
     };
 
@@ -79,7 +79,7 @@ namespace odb
       key_init ();
 
     private:
-      static once once_;
+      static win32_once_t once_;
       static std::size_t key_;
     };
 
diff --git a/odb/details/win32/tls.txx b/odb/details/win32/tls.txx
index 025e7cb..4290a35 100644
--- a/odb/details/win32/tls.txx
+++ b/odb/details/win32/tls.txx
@@ -16,7 +16,7 @@ namespace odb
     // tls<T>
     //
     template <typename T>
-    once tls<T>::once_;
+    win32_once_t tls<T>::once_= WIN32_ONCE_INIT;
 
     template <typename T>
     size_t tls<T>::key_;
@@ -25,7 +25,7 @@ namespace odb
     T& tls<T>::
     get () const
     {
-      once_.call (key_init);
+      win32_once (once_, key_init);
 
       if (void* v = _get (key_))
         return *static_cast<T*> (v);
@@ -42,7 +42,7 @@ namespace odb
     void tls<T>::
     free ()
     {
-      once_.call (key_init);
+      win32_once (once_, key_init);
 
       if (void* v = _get (key_))
       {
@@ -68,7 +68,7 @@ namespace odb
     // tls<T*>
     //
     template <typename T>
-    once tls<T*>::once_;
+    win32_once_t tls<T*>::once_ = WIN32_ONCE_INIT;
 
     template <typename T>
     size_t tls<T*>::key_;
@@ -77,7 +77,7 @@ namespace odb
     T* tls<T*>::
     get () const
     {
-      once_.call (key_init);
+      win32_once (once_, key_init);
       return static_cast<T*> (_get (key_));
     }
 
@@ -85,7 +85,7 @@ namespace odb
     void tls<T*>::
     set (T* p)
     {
-      once_.call (key_init);
+      win32_once (once_, key_init);
       _set (key_, p);
     }