编译代码时出错了。我想头文件没有正确链接，因为那些错误的变量中的每一个都已在'variables.h'中指定，我正确#include。奇怪的是，如果我评论在main.cpp中使用变量的区域，则另一个文件readfile.cpp中的相同变量会弹出另外一大堆错误。下面是错误输出，以及main.cpp和variables.h的代码。有什么想法吗？
g++ -c main.cpp
g++ -c readfile.cpp
g++ -c Objects.cpp
g++ -o raytracer main.o readfile.o Objects.o
Undefined symbols for architecture x86_64:
"_depth", referenced from:
init() in main.o
readFile(char const*)in readfile.o
"_diffuse", referenced from:
readFile(char const*)in readfile.o
"_emission", referenced from:
readFile(char const*)in readfile.o
"_filename", referenced from:
init() in main.o
"_fov", referenced from:
init() in main.o
initCamera(float*)in readfile.o
"_height", referenced from:
init() in main.o
readFile(char const*)in readfile.o
"_lookatx", referenced from:
init() in main.o
initCamera(float*)in readfile.o
"_lookaty", referenced from:
init() in main.o
initCamera(float*)in readfile.o
"_lookatz", referenced from:
init() in main.o
initCamera(float*)in readfile.o
"_lookfromx", referenced from:
init() in main.o
initCamera(float*)in readfile.o
"_lookfromy", referenced from:
init() in main.o
initCamera(float*)in readfile.o
"_lookfromz", referenced from:
init() in main.o
initCamera(float*)in readfile.o
"_maxvertnorms", referenced from:
init() in main.o
readFile(char const*)in readfile.o
"_maxverts", referenced from:
init() in main.o
readFile(char const*)in readfile.o
"_shininess", referenced from:
readFile(char const*)in readfile.o
"_specular", referenced from:
readFile(char const*)in readfile.o
"_spherecount", referenced from:
init() in main.o
"_spheres", referenced from:
readFile(char const*)in readfile.o
"_triangles", referenced from:
readFile(char const*)in readfile.o
"_tricount", referenced from:
init() in main.o
"_trinormals", referenced from:
readFile(char const*)in readfile.o
"_trinormcount", referenced from:
init() in main.o
"_upx", referenced from:
init() in main.o
initCamera(float*)in readfile.o
"_upy", referenced from:
init() in main.o
initCamera(float*)in readfile.o
"_upz", referenced from:
init() in main.o
initCamera(float*)in readfile.o
"_vertexcount", referenced from:
init() in main.o
"_vertexnormcount", referenced from:
init() in main.o
"_vertices", referenced from:
readFile(char const*)in readfile.o
"_vertnormals", referenced from:
readFile(char const*)in readfile.o
"_width", referenced from:
init() in main.o
readFile(char const*)in readfile.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
下面是variables.h ..
#include "vertexnormal.h"
#include "sphere.h"
#include "tri.h"
#include "trinormal.h"
#include "vec.h"
#include <string>
#include <vector>
using namespace std;
// width and height specify image size
extern float width;
extern float height;
// maximum depth for a ray (level of recursion)
extern int depth;
// the output file to which the image should be written
extern string filename;
// camera specifiations (should i put in a struct?)
extern float lookfromx;
extern float lookfromy;
extern float lookfromz;
extern float lookatx;
extern float lookaty;
extern float lookatz;
extern float upx;
extern float upy;
extern float upz;
extern float fov;
//***************************//
// Geometry Specifications //
//***************************//
// specifies the number of vertrices for tri specifications
extern int maxverts;
// specifies the number of vertices with normals for tri specifications
extern int maxvertnorms;
// pile of inputted vertices
// might need to #include glm file
extern vector<vec> vertices;
// pile of inputted vertices with specified normals
extern vector<vertexNormal> vertnormals;
// pile of inputted spheres
extern vector<sphere> spheres;
// pile of inputted triangles
extern vector<tri> triangles;
// pile of inputted triangles using vertices with specified normals
extern vector<triNormal> trinormals;
extern int vertexcount;
extern int vertexnormcount;
extern int spherecount;
extern int tricount;
extern int trinormcount;
//**************************//
// Materials Specifiations //
//**************************//
extern float diffuse[3];
extern float specular[3];
extern float shininess;
extern float emission[3];
这是我的main.cpp，
#include <iostream>
#include <string>
#include <fstream>
#include <sstream>
#include "Objects.h"
using namespace std;
#include "readfile.h"
#include "variables.h"
void init() {
cout << "Reading in scene file... \n";
cout << "Image size has been set to a " << width << " x " << height << " output. /n";
cout << "The maximum recursion depth has been set to " << depth << ". \n";
cout << "The image will be output to " << filename << ".png. \n";
cout << "The camera has been instantiated with the following properties: \n";
cout << "\t POSITION: (" << lookfromx << ", " << lookfromy << ", " << lookfromz << ") \n";
cout << "\t DIRECTION: (" << lookatx << ", " << lookaty << ", " << lookatz << ") \n";
cout << "\t UP: (" << upx << ", " << upy << ", " << upz << ") \n";
cout << "\t FIELD OF VIEW: " << fov << " \n";
cout << "An amount of " << vertexcount << " vertices has been specified with a maximum of " << maxverts << " allowed. \n";
cout << "An amount of " << vertexnormcount << " vertices with normals has been specified with a maximum of " << maxvertnorms << " allowed. \n";
cout << "An amount of " << spherecount << " spheres have been specified. \n";
cout << "An amount of " << tricount << " triangles have been specified. \n";
cout << "An amount of " << trinormcount << " triangles with calculated vertex normals have been specified. \n";
}
int main (int argc, char * argv[]) {
readFile(argv[1]);
init();
return 0;
}
答案 0 :(得分：3)
试试这个：
extern变量声明。extern。extern的工作原理。有些东西告诉我你在学习中错过了。好的，这已经涵盖了几千次，但对于OP：
声明存在变量
// DECLARE myvar, an int variable. no storage has been set aside
// this is simply telling the compiler this thing exists.. somewhere.
extern int myvar;
定义变量的存在
// DEFINE myvar, an int variable. storage *is* set aside here.
// only ONE of these, by this name, can be in your global
// namespace in your program.
int myvar = 0;
传统上，extern声明位于标题中，但c / cpp文件中的定义始终。 必须是您程序中使用的任何extern声明变量的匹配定义。
这如何适合您的情况
所有变量都在variables.h中声明，但无论如何都不会定义。通过告诉您将所有这些声明复制/粘贴到源文件中（任何都可以;我选择了main.cpp，因为它已经在您的项目中），然后删除 extern关键字在该源文件（不是标题）中，您基本上定义，它们都正式存在。现在，在其他源文件中对extern'ed变量的所有引用最终都会在链接时连接到某些内容。
<强>边栏
在您的变量已定义的c / cpp文件中，请确保将其初始化为正确的值。这是唯一可以做到的地方。你不能在任何extern声明中做到这一点。它只能在定义。
标头文件
extern int myvar; // note: no initial value.
源文件
int myvar = 0; // note: initialized to zero (0)
我希望至少有点意义。
答案 1 :(得分：0)
extern float lookfromx;
extern float lookfromy;
extern float lookfromz;
extern float lookatx;
extern float lookaty;
extern float lookatz;
这些只是声明。您需要在程序中的某个位置定义这些变量（例如，在variables.cpp中）。要制作这些定义，您可以
删除extern关键字
添加初始化程序（=值;）
答案 2 :(得分：0)
您的variable.h文件只是使您的变量可以在全局范围内的其他文件中移植，但仍然需要声明它们。确保在主文件中声明实际变量（正常的初始化方法）。
extern关键字声明一个变量或函数，并指定它具有外部链接（其名称可以从其定义的文件以外的文件中看到）。修改变量时，extern指定变量具有静态持续时间（在程序开始时分配，在程序结束时分配）。变量或函数可以在另一个源文件中定义，或者稍后在同一文件中定义。默认情况下，文件范围内的变量和函数声明是外部的。