GCC plugins

hello
  print "hello" on the screen

myplugin1
  print AST tree

nullpointer1
  scan for null pointer dereferencing.
  example:
    if (ab || ab->a == 0)

dump-tree-xml
  dump AST tree in xml format

Note:
  A working GCC development environment is needed.
  I use this command to configure:
    ../configure --enable-languages=c,c++ --disable-multilib --enable-checks=all --program-suffix=-dev