[vtk-developers] possible bug in vtkErrorMacro and vtkWarningMacro

[Ken Martin]

It works because our convention is that the contents of those macros start
with a string, or if not a string then a <<. Consider two examples

vtk...Macro("Why do birds suddenly appear?");

expands to "): " "Why do ...."  and the preprocessor concatenates the two
strings making it valid code.  The second example is

vtk...Macro(<< *vtkInstance << "hmmm");

which expands out to "): " << *vtkInstance << ...

which is also valid code.

Ken


Ken Martin PhD 
Kitware Inc.
28 Corporate Drive
Clifton Park NY 12065
518 371 3971 

-----Original Message-----
From: vtk-developers-bounces+ken.martin=kitware.com at vtk.org
[mailto:vtk-developers-bounces+ken.martin=kitware.com at vtk.org] On Behalf Of
Amy Squillacote
Sent: Friday, May 25, 2007 9:34 AM
To: Vtk Developers
Subject: [vtk-developers] possible bug in vtkErrorMacro and vtkWarningMacro

Hi All,

Earlier today, someone pointed out to me a possible bug in vtkErrorMacro 
and vtkWarningMacro; see below.

#define vtkErrorMacro(x)                        \
   vtkErrorWithObjectMacro(this,x)

//
// This macro is used to print out errors
// vtkErrorWithObjectMacro(self, << "Error message" << variable);
//
#define vtkErrorWithObjectMacro(self, x)                        \
   {                                                            \
   if (vtkObject::GetGlobalWarningDisplay())                    \
     {                                                          \
     vtkOStreamWrapper::EndlType endl;                          \
     vtkOStreamWrapper::UseEndl(endl);                          \
     vtkOStrStreamWrapper vtkmsg;                               \
     vtkmsg << "ERROR: In " __FILE__ ", line " << __LINE__      \
            << "\n" << self->GetClassName() << " (" << self     \
            << "): " x << "\n\n";                               \    
<----- offending line
    ...
   }

Shouldn't the line indicated above actually be the following (adding 
"<<" before "x")?
<< "): " << x << "\n\n";                               \

Similar code can also be found in the vtkWarningMacro. It looks like a 
bug to me, but at the same time it's hard to believe that it's actually 
a bug because of how much those two macros are successfully used. 
According to cvs annotate, that line has been that way since December 
2002. Do you think it's a bug? If not, why not?

- Amy

-- 
Amy Squillacote
Kitware, Inc.
28 Corporate Drive
Clifton Park, NY 12065
Phone: (518) 371-3971 x106

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