c++ - 在包含保护中包含其他标头会导致错误

Answer 1

好的。实际问题与未提及的文件Shape.cpp有关，其中当然包括，以及在警卫之前Shape.h移动正在解决问题的事实。#include "GLProject.h"防护内包含指令的流程：

Shape.h (def guard)
     GProject.h (def guard) 
          ...(MainWindow.h and ShaderProgram.h)...//not interesting

          Shape.h (omit, because of guard)

          Scene.h
                GProject.h (omit, because of guard)
          back to Scene.h (def guard) ERROR

在外面使用指令时：

Shape.h
     GProject.h (def guard)
          ...(MainWindow.h and ShaderProgram.h)...//not interesting

          Shape.h
                GProject.h (omit, cause of guard)
          back to Shape.h (now def guard and class)

          Scene.h
                GProject.h (omit, because of guard)
          back to Scene.h (def guard) No error - Shape defined