形如: float a = -3.0; float b = fabs(a); 形参数据类型和实参数据类型完全一致,却还报警告: incompatible implicit declaration of built-in function 'fabs' 只要包含头文件#include <math.h>就好了 还有这种警告: warning: implicit declaration of function '' [-Wimplicit-function-declaration] 也是需要包含头文…