My intention is to have own naming rules in eclipse editor for C programming Ex: a function should start with File name, it shall contain maximum of 20 character- FILENAME_MaxOf20Char().
When it is violated has to show an warning.
To do this tried to extend org.eclipse.cdt.core.IErrorParser. But this one is parsing from compilor output.
IErrorParser is not the right extension point to use for this.
You want to use the Code Analysis (CodAn) framework and write a custom checker. See this page for documentation.