This change avoid the redefinitions of log categories. To do this, the parent category of a subcategory must be declared extern instead
public data (see the definition of the macro XBT_LOG_NEW_SUBCATEGORY). An other change corrects the definition of the macro
XBT_LOG_NEW_ROOT_SUBCATEGORY. Indeed, Ansi C (Visual C++ compiler standard language) doesn't allow to initialize a structure during
its declaration with non constant values.
git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/simgrid/simgrid/trunk@4979
48e7efb5-ca39-0410-a469-
dd3cf9ba447f
