[Insight-developers] more VC++ idiosyncrasies

[Bill Hoffman]

The microsoft compiler is wrong, and the version of code you suggest,
will not compile on any compiler except the microsoft one.
The standard says that the scope is limited to the for loop, so:

foo()
{
for(int i =0;...)
;
// i is undefined by the standard at this point
for(i=0; ...)
}

The #define is used in vxl for broken compilers.   


Of course this code:
int i;
for(i =...)
for(i =...)

is fine with any compiler.

-Bill

At 07:57 AM 12/4/00 -0500, you wrote:
>The C and C++ standards have changed back and forth on this often enough that I can never remember
>what the current "standard" is for loop variables.  At one time, loop variables were limited in scope
>to the loop, so the code referenced here was legal.
>
>Rather than change the compiler option or use a #define to remap "for", I suggest we just change the
>code so that we do not use this construct, i.e. do not declare the same variable in the
>initialization clause of a "for" loop multiple times in routine.
>
>So the code,
>
>for (int i=0; i < ...; i++)
>   {
>   // some code
>   }
>
>for (int i=0; i < ...; i++)
>   {
>   // some other code
>   }
>
>would be discouraged.  But code like
>
>for (int i=0; i < ...; i++)
>   {
>   // some code
>   }
>
>for (i=0; i < ...; i++)
>   {
>   // some other code
>   }
>
>would still be legal ("i" is only declared once).
>
>
>
>
>
>
>-----Original Message-----
>From: Lydia Ng [mailto:lng@statsci.com]
>Sent: Friday, December 01, 2000 10:11 PM
>To: insight-developers@public.kitware.com
>Subject: [Insight-developers] more VC++ idiosyncrasies
>
>
>Hi,
>
>I get an error when I try to compile itkImportImageTest.cxx in VC++.
>It complains about the redefinition of the loop variable i in
>line 90 of itkShrinkImage.txx. The error message is attached below.
>
>This is yet another C++ standard noncompliance problem,
>worst still it happens intermittently as there is lots of other code
>where the loop variable has been used more than once.
>
>They have a fix in:
>http://support.microsoft.com/support/kb/articles/Q167/7/48.ASP
>
>where they suggest to either:
>     a) set compiler option /Za
>
>This causes more compile errors.
>
>     b) #defining the "for" keyword as follows:
>             #define for if(0); else for
>
>The #defining seems to work.
>If this is the only solution, we probably need to stick it
>in some VC++ related makefile.
>
>BTW, when I run itkImportImageTest in Release mode (after adding the
>#define) I get an
>access violation due to the CopyInformation() problem.
>Running itkImportImageTest on Cygwin also results in an access violation
>- but I haven't stepped through it to see if it the same problem.
>
>Lydia
>
>--------------------Configuration: itkImportImageTest - Win32
>Release--------------------
>Compiling...
>itkImportImageTest.cxx
>F:\lng\projects\Insight-clean\Insight/Code/Common\itkMultiThreader.h(233) :
>warning C4251: 'm_SpawnedThreadActiveFlagLock' : class
>'itk::SmartPointer<class itk::MutexLock>' needs to have dll-interface to be
>used by clients of class 'itk::MultiThread
>er'
>F:\lng\projects\Insight-clean\Insight/Code/Common\itkProcessObject.h(342) :
>warning C4251: 'm_Inputs' : class 'std::vector<class itk::SmartPointer<class
>itk::DataObject>,class std::allocator<class itk::SmartPointer<class
>itk::DataObject> > >' needs
>to have dll-interface to be used by clients of class 'itk::ProcessObject'
>F:\lng\projects\Insight-clean\Insight/Code/Common\itkProcessObject.h(348) :
>warning C4251: 'm_Outputs' : class 'std::vector<class
>itk::SmartPointer<class itk::DataObject>,class std::allocator<class
>itk::SmartPointer<class itk::DataObject> > >' needs
>  to have dll-interface to be used by clients of class 'itk::ProcessObject'
>F:\lng\projects\Insight-clean\Insight/Code/Common\itkProcessObject.h(371) :
>warning C4251: 'm_Threader' : class 'itk::SmartPointer<class
>itk::MultiThreader>' needs to have dll-interface to be used by clients of
>class 'itk::ProcessObject'
>F:\lng\projects\Insight-clean\Insight/Code/Common\itkShrinkImage.txx(90) :
>error C2374: 'i' : redefinition; multiple initialization
>
>F:\lng\projects\Insight-clean\Insight/Code/Common\itkShrinkImage.txx(76) :
>see declaration of 'i'
>         C:\Program Files\Microsoft Visual Studio\VC98\INCLUDE\xstring(583) :
>while compiling class-template member function 'void __thiscall
>itk::ShrinkImage<class itk::Image<short,2,class
>itk::ImportImageContainer<unsigned long,short> >,class itk::
>Image<class itk::Scalar<short>,2,class itk::ValarrayImageContainer<unsigned
>long,class itk::Scalar<short> > > >::ThreadedGenerateData(const class
>itk::ImageRegion<2> &,int)'
>Error executing cl.exe.
>
>itkImportImageTest.exe - 1 error(s), 4 warning(s)
>
>
>
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