QGlobal: static_assert that sizeof(int) == 4 and UCHAR_MAX == 255

According to Thiago, Qt assumes this in a lot of places,
so make it explicit.

Change-Id: I3f4a55699379fd9fe4d792061c80b3b589c10c53
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/global/qglobal.cpp

@@ -88,6 +88,14 @@ Q_CORE_EXPORT void *qMemCopy(void *dest, const void *src, size_t n);
 Q_CORE_EXPORT void *qMemSet(void *dest, int c, size_t n);
 #endif
 
+// Statically check assumptions about the environment we're running
+// in. The idea here is to error or warn if otherwise implicit Qt
+// assumptions are not fulfilled on new hardware or compilers
+// (if this list becomes too long, consider factoring into a separate file)
+Q_STATIC_ASSERT_X(sizeof(int) == 4, "Qt assumes that int is 32 bits");
+Q_STATIC_ASSERT_X(UCHAR_MAX == 255, "Qt assumes that char is 8 bits");
+
+
 /*!
     \class QFlag
     \inmodule QtCore