I log out the excute order of render funcs,it apearently does not match the official doc
here are they

That is typical. You would expect OnPostRender to never occur before OnRenderObject. Which version of Unity? Might be good to attach a demo project, so we can test on multiple versions of Unity and file a bug report if needed.
Thanks,unity 2017.1.0f3, RenderFuncs.cs is attached on Camera,and ObjFuncs.cs should be attached to a GameObject has MeshFilter Component