小编use*_*241的帖子

/usr/include/i386-linux-gnu/bits/mathcalls.h:311:1: error: ambiguates old declaration ‘double round(double)’
g.cpp: In function ‘int round(double)’:
g.cpp:14:24: error: new declaration ‘int round(double)’
/usr/include/i386-linux-gnu/bits/mathcalls.h:311:1: error: ambiguates old declaration ‘double round(double)’

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#include <iostream>
#include <cmath>
using namespace std;

int round(double number);

int main()
{
    double number = 5.9;
    round(number);
    return 0;
}
int round(double number)
{
    return static_cast<int>(floor(number + 0.5));
}

为什么我的编译器显示错误