dolfin team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

On Tuesday 25 March 2008 13:38:22 Martin Sandve Alnæs wrote:
> 2008/3/25, Anders Logg <logg@xxxxxxxxx>:
> > On Tue, Mar 25, 2008 at 01:18:39PM +0100, Martin Sandve Alnæs wrote:
> >  > 2008/3/25, Anders Logg <logg@xxxxxxxxx>:
> >  > >  There are quite a few of these already (but they are missing in
> >  > > many places). For example, here is PETScMatrix::get:
> >  > >
> >  > >   void PETScMatrix::get(real* block,
> >  > >                         uint m, const uint* rows,
> >  > >                         uint n, const uint* cols) const
> >  > >   {
> >  > >     dolfin_assert(A);
> >  > >     MatGetValues(A,
> >  > >                  static_cast<int>(m),
> >  > >                  reinterpret_cast<int*>(const_cast<uint*>(rows)),
> >  > >                  static_cast<int>(n),
> >  > >                  reinterpret_cast<int*>(const_cast<uint*>(cols)),
> >  > >                  block);
> >  > >   }
> >  > >
> >  > >  Is this what you have in mind?
> >  >
> >  > Looks good. Will dolfin_assert result in an exception or just kill the
> >  > application? An informative error message and stack trace is nice to
> >  > have.
> >
> > It will throw a runtime error. (I think Ola or you fixed this.)
> >  Check in dolfin/log/log.h where dolfin_assert is defined. It will
> >  ultimately call Logger::__assert:
> >
> >  void Logger::__assert(std::string msg)
> >  {
> >   std::string s = std::string("*** Assertion ") + msg;
> >   throw std::runtime_error(s);
> >
> > }
> >
> >  > Will the code be removed in release builds or not?
> >
> > Depends on how the builds are made, but dolfin_assert() is only active
> >  when DEBUG is defined:
> >
> >  #ifdef DEBUG
> >  #define dolfin_assert(check) do { if ( !(check) )
> >  #dolfin::__dolfin_assert(__FILE__, __LINE__, __FUNCTION__, "(" #check
> > ")"); } while (false) #else
> >  #define dolfin_assert(check)
> >  #endif
> >
> >
> >  --
> >  Anders
>
> Looks good. But a lot of error checks / assertions should always be
> kept though, there's no reason to remove them where they don't impact
> performance. Maybe there should be a release version of dolfin_assert
> with a different name, dolfin_assert_release or dolfin_check or
> something?
>
> But what's the point of the "do { ... } while(false);" ??
> { ... } or just ... should be the same thing as far as I can see.

It's because macros are evil! :)

http://www.parashift.com/c++-faq-lite/misc-technical-issues.html#faq-39.4

It looks like macros with if statements have a risk of nesting with the wrong 
if, if it is used inside an other if statement. (Nice sentence! :) )

Johan