   precomiler - head and recomplie
  when I use (Yu) precomipler - head , and I disable the usage of precompiler-head to some specific cpp file. I found if I change code in the specific cpp file, I must recompile all project(maybe recompile precompiler-head ).if you just change the code in file that use precomiler-head, you just recompile the file, all is ok. why? bug?    