问 这是源程序
#include "C:\Program Files\ARM\ADSv1_2\Include\math.h"

int main (void)
{
    long i, j;
    
    i = -5;
    j = sin(i);   //line 6
    j = abs(i);   //line7

    return 0;
}
========================================================
编译结果：
Warning: c2207w: inventing 'extern int abs();'
-------------------------------------------------------
line6 正确
line7 说函数没定义
==========================================================
math.h中的源代码：
.........
    inline long double abs(long double __x) // fabsl
                { return (long double)abs((double) __x); }
.........
    inline long double sin(long double __x) //sinl
                { return (long double)sin((double) __x); }