Re: [ROOT] '+' in LinkDef

From: Rene Brun (
Date: Fri Oct 26 2001 - 17:56:19 MEST

Hi Thomas,

When using the "+" option in the pragma statement of a LinkDef file,
you instruct rootcint to generate enough dictionary information such that
the I/O  system with AUTOMATIC SCHEMA EVOLUTION that we introduced
in version 3 can be used. When using this option, the Streamer functions
invoke the functions ReadBuffer and WriteBuffer from TClass that take care
of streaming "out" and in particular "in" using the dictionary information.
If the "+" option is not specified, the old code with statements like
  R__b << member;
is generated. In this case, you have to deal yourself with the problems
of schema evolution.

Unless you have good reasons to implement the Streamer function yourself,
you should always use the option "+"

We could not set this option by default when we introduced version 3.

Rene Brun

Thomas Bretz wrote:
> Hello rooters,
> what is the advantage of using the '+' in the pragma statement of my
> LinkDef.h file? (What is the advatage of the 'new streamer'?)
> Regards,
> Thomas.

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