C++ previous definition error
问题 So, thanks to this website, I found the answer to my previous problem. I'm adding a function to a class in a GNU automake project that uses a pointer to a doc object. Dependencies were included in the Makefile.am file to include doc.h and plsa.h in the respective order. However, when I compiled, I would get a doc has not been declared error. Then, I tried adding the #include statement here, which gives a previous redefinition of 'class doc' error. I learned that I have to declare doc by using