[glib/glib-2-42] Avoid warning when using G_STMT_END macro with MSVC

[Paolo Borelli <pborelli src gnome org>]

commit b2c0f526008fa709af84d6e5699d581688365392
Author: Paolo Borelli <pborelli gnome org>
Date:   Tue Jan 13 12:44:20 2015 +0100

    Avoid warning when using G_STMT_END macro with MSVC
    
    Workaround found on
    http://cnicholson.net/2009/03/stupid-c-tricks-dowhile0-and-c4127/
    
    https://bugzilla.gnome.org/show_bug.cgi?id=742851

 glib/gmacros.h |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)
---
diff --git a/glib/gmacros.h b/glib/gmacros.h
index 0bdfa55..7320228 100644
--- a/glib/gmacros.h
+++ b/glib/gmacros.h
@@ -279,11 +279,21 @@
  *   if (x) G_STMT_START { ... } G_STMT_END; else ...
  * This intentionally does not use compiler extensions like GCC's '({...})' to
  * avoid portability issue or side effects when compiled with different compilers.
+ * MSVC complains about "while(0)": C4127: “Conditional expression is constant”,
+ * so we use __pragma to avoid the warning since the use here is intentional.
  */
 #if !(defined (G_STMT_START) && defined (G_STMT_END))
 #define G_STMT_START  do
+#if defined (_MSC_VER) && (_MSC_VER >= 1500)
+#define G_STMT_END \
+    __pragma(warning(push)) \
+    __pragma(warning(disable:4127)) \
+    while(0) \
+    __pragma(warning(pop))
+#else
 #define G_STMT_END    while (0)
 #endif
+#endif
 
 /* Deprecated -- do not use. */
 #ifndef G_DISABLE_DEPRECATED