warning: control reaches end of non-void function 和 warning: implicit declaration of function 'rsgClearColor' is invalid in C99

#pragma version(1)
#pragma rs java_package_name(com.lenovo.vcs.test1)

//脚本实例创建时自动调用
void init(){
}

int root(){
    float red = rsRand(1.0f);
    float green = rsRand(1.0f);
    float blue = rsRand(1.0f);
    
    //清除随机颜色的背景色
    rsgClearColor(red,green,blue,1.0f);　　　　//出错误警告  warning: implicit declaration of function ‘rsgClearColor‘ is invalid in C99
    
    //每秒50帧 = 每帧20毫秒
    return 20;
}