synchronize GTK2 minimum version in docs

[wxWidgets.git] / include / wx / tls.h

diff --git a/include/wx/tls.h b/include/wx/tls.h
index 9d1d6373b3e2da265a5f8413ca7bb2371afd17f9..6886434c007fa34b71d52d5017348f5bf5b8e502 100644 (file)
--- a/include/wx/tls.h
+++ b/include/wx/tls.h
@@ -17,13 +17,27 @@
 // check for compiler support of thread-specific variables
 // ----------------------------------------------------------------------------
 
-#ifdef HAVE___THREAD_KEYWORD
+// when not using threads at all, there is no need for thread-specific
+// values to be really thread-specific
+#if !wxUSE_THREADS
+    #define wxHAS_COMPILER_TLS
+    #define wxTHREAD_SPECIFIC_DECL
+// otherwise try to find the compiler-specific way to handle TLS unless
+// explicitly disabled by setting wxUSE_COMPILER_TLS to 0 (it is 1 by default).
+#elif wxUSE_COMPILER_TLS
+// __thread keyword is not supported correctly by MinGW, at least in some
+// configurations, see http://sourceforge.net/support/tracker.php?aid=2837047
+// and when in doubt we prefer to not use it at all.
+#if defined(HAVE___THREAD_KEYWORD) && !defined(__MINGW32__)
     #define wxHAS_COMPILER_TLS
     #define wxTHREAD_SPECIFIC_DECL __thread
+// MSVC has its own version which might be supported by some other Windows
+// compilers, to be tested
 #elif wxCHECK_VISUALC_VERSION(7)
     #define wxHAS_COMPILER_TLS
     #define wxTHREAD_SPECIFIC_DECL __declspec(thread)
-#endif
+#endif // compilers
+#endif // wxUSE_COMPILER_TLS
 
 // ----------------------------------------------------------------------------
 // define wxTLS_TYPE()
@@ -31,9 +45,19 @@
 
 #ifdef wxHAS_COMPILER_TLS
     #define wxTLS_TYPE(T) wxTHREAD_SPECIFIC_DECL T
+    #define wxTLS_PTR(var) (&(var))
+    #define wxTLS_VALUE(var) (var)
 #else // !wxHAS_COMPILER_TLS
-    #ifdef __WXMSW__
+
+    extern "C"
+    {
+        typedef void (*wxTlsDestructorFunction)(void*);
+    }
+
+    #if defined(__WINDOWS__)
         #include "wx/msw/tls.h"
+    #elif defined(__OS2__)
+        #include "wx/os2/tls.h"
     #elif defined(__UNIX__)
         #include "wx/unix/tls.h"
     #else
@@ -41,23 +65,69 @@
         #error Neither compiler nor OS support thread-specific variables.
     #endif
 
-    // wxTlsValue<T> represents a thread-specific value of type T
+    #include <stdlib.h> // for calloc()
+
+    // wxTlsValue<T> represents a thread-specific value of type T but, unlike
+    // with native compiler thread-specific variables, it behaves like a
+    // (never NULL) pointer to T and so needs to be dereferenced before use
+    //
+    // Note: T must be a POD!
+    //
+    // Note: On Unix, thread-specific T value is freed when the thread exits.
+    //       On Windows, thread-specific values are freed later, when given
+    //       wxTlsValue<T> is destroyed.  The only exception to this is the
+    //       value for the main thread, which is always freed when
+    //       wxTlsValue<T> is destroyed.
     template <typename T>
     class wxTlsValue
     {
     public:
         typedef T ValueType;
 
-        wxTlsValue() { *this = static_cast<T>(0); }
+        // ctor doesn't do anything, the object is created on first access
+        wxTlsValue() : m_key(free) {}
 
-        wxTlsValue& operator=(T value)
+        // dtor is only called in the main thread context and so is not enough
+        // to free memory allocated by us for the other threads, we use
+        // destructor function when using Pthreads for this (which is not
+        // called for the main thread as it doesn't call pthread_exit() but
+        // just to be safe we also reset the key anyhow)
+        ~wxTlsValue()
         {
-            m_key.Set(wxUIntToPtr(value));
+            if ( m_key.Get() )
+                m_key.Set(NULL); // this deletes the value
+        }
 
-            return *this;
+        // access the object creating it on demand
+        ValueType *Get()
+        {
+            void *value = m_key.Get();
+            if ( !value )
+            {
+                // ValueType must be POD to be used in wxHAS_COMPILER_TLS case
+                // anyhow (at least gcc doesn't accept non-POD values being
+                // declared with __thread) so initialize it as a POD too
+                value = calloc(1, sizeof(ValueType));
+
+                if ( !m_key.Set(value) )
+                {
+                    free(value);
+
+                    // this will probably result in a crash in the caller but
+                    // it's arguably better to crash immediately instead of
+                    // slowly dying from out-of-memory errors which would
+                    // happen as the next access to this object would allocate
+                    // another ValueType instance and so on forever
+                    value = NULL;
+                }
+            }
+
+            return static_cast<ValueType *>(value);
         }
 
-        operator T() const { return wxPtrToUInt(m_key.Get()); }
+        // pointer-like accessors
+        ValueType *operator->() { return Get(); }
+        ValueType& operator*() { return *Get(); }
 
     private:
         wxTlsKey m_key;
@@ -66,6 +136,8 @@
     };
 
     #define wxTLS_TYPE(T) wxTlsValue<T>
+    #define wxTLS_PTR(var) ((var).Get())
+    #define wxTLS_VALUE(var) (*(var))
 #endif // wxHAS_COMPILER_TLS/!wxHAS_COMPILER_TLS
 
 #endif // _WX_TLS_H_