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1.请问这句话：#ifndef SPLL_1ph_SOGI_IQ_H_什么意思，ifndef是什么意思。
如果没有定义这个符号SPLL_1ph_SOGI_IQ_H_
Eric
#ifndef X，这是if not define的简称，判断X是否被宏定义过，通常的用法是
