Re: typeid(cls).name() problem

On Mon, 21 Feb 2005 14:07:22 +0300
"Vyacheslav Frolov" <v.frolov@xxxxxxxxx> wrote:

> Craig Southeren wrote:
> > I've just tried it here on a dual 466 PII running RedHat 9 with no
> > problems. Multiple runs gave nothing but lots of dots.
> 
> It's OK. Can you try it on Windows?

I can't put Windows on the dual processor machine I just used because I
need it running Linux right now. 

And I do not own a machine with a hyperthreaded processor 

Sorry....

> > What string does the Class() function return when it fails?
> 
> It returns garbage.
> Atteched the output of rttitest.bat on w2k with HyperThreading enabled.

After, some careful reading of the Microsoft documentation and a lot of
reading between the lines, I think I know that the problem is.

The Class member function for any PObject derived class ends looks like
this:

    static inline const char * Class()
      { return PCLASSNAME(cls); } 

The PCLASSNAME function looks like this

    #define   PCLASSNAME(cls) (6+typeid(cls).name())

In the MS environment, the typeid structure is not a static object. So,
this code effectively returns a temporary pointer. This does not happen
on Linux because we use a different method for getting the class name

We could just use the same method as Linux, but I'm not keen on that
because may result in wasted strings.

The following patch uses templates - let me know how it goes:

Index: include/ptlib/msos/ptlib/contain.h
===================================================================
RCS file: /cvsroot/openh323/pwlib/include/ptlib/msos/ptlib/contain.h,v
retrieving revision 1.50
diff -u -r1.50 contain.h
--- include/ptlib/msos/ptlib/contain.h  30 Oct 2004 19:23:45 -0000      1.50
+++ include/ptlib/msos/ptlib/contain.h  21 Feb 2005 12:50:11 -0000
@@ -463,7 +463,16 @@
 #endif
 
 #define   P_HAS_TYPEINFO  1
-#define   PCLASSNAME(cls) (6+typeid(cls).name())
+#define   PBASECLASSNAME(cls) (6+typeid(cls).name())
+
+template <class Cls>
+const char * PClassNameTemplate()
+{
+  static std::string str(PBASECLASSNAME(Cls));
+  return str.c_str();
+}
+
+#define   PCLASSNAME(cls) PClassNameTemplate<cls>()
 
    Craig

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