Map file structure

Am creating a debugger tool.
I need the MAP file Structure specification for GCC compiler.
In order to find how the memory is mapped for different variables of different Data types (class, inner class, static, static const, extern, template, typedef Variables Specification in MAP file).
And also i want to know the way how the symbols are added to different variable to differentiate in the MAP file.
Tell me the way to proceed.

Start by downloading the gcc source code and documentation