[英]c++ linux compile error: undefined reference to `main'
I have looked for this error and tried a few of the solutions, but have not found anything, at this point I would just like to compile it. 我已经找了这个错误并尝试了一些解决方案,但没有找到任何东西,此时我只想编译它。
The error I am getting is: 我得到的错误是:
/usr/lib/gcc/i486-linux-gnu/4.4.1/../../../../lib/crt1.o: In function `_start':
/build/buildd/eglibc-2.10.1/csu/../sysdeps/i386/elf/start.S:115: undefined reference to `main'
using: 使用:
g++ -lglut Solar.cpp
the code is here: 代码在这里:
using namespace std;
#include <stdio.h>
#include <GL/glut.h>
#include "math.h"
class Solar {
int main(){
initializeGL();
//Stars Alpha = new Stars(5.0);
//Stars *Alpha = new Stars(5.0);
//Planets *Awe = new Planets(.6,2,30,"Awe",0.0,0.0,0.0);
paintGL();
return 0;
}
vid initializeGL(){
glShadeModel(GL_SMOOTH);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClearDepth(1.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
// lighting stuff
GLfloat ambient[] = {0.0, 0.0, 0.0, 1.0};
GLfloat diffuse[] = {0.9, 0.9, 0.9, 1.0};
GLfloat specular[] = {0.4, 0.4, 0.4, 1.0};
GLfloat position0[] = {1.0, 1.0, 1.0, 0.0};
glLightfv( GL_LIGHT0, GL_POSITION, position0 );
glLightfv( GL_LIGHT0, GL_AMBIENT, ambient );
glLightfv( GL_LIGHT0, GL_DIFFUSE, diffuse );
glLightfv( GL_LIGHT0, GL_SPECULAR, specular );
GLfloat position1[] = {-1.0, -1.0, -1.0, 0.0};
glLightfv( GL_LIGHT1, GL_POSITION, position1 );
glLightfv( GL_LIGHT1, GL_AMBIENT, ambient );
glLightfv( GL_LIGHT1, GL_DIFFUSE, diffuse );
glLightfv( GL_LIGHT1, GL_SPECULAR, specular );
glEnable( GL_LIGHTING );
glEnable( GL_LIGHT0 );
glEnable( GL_LIGHT1 );
glEnable( GL_COLOR_MATERIAL );
/* Draws the Grid*/
drawRGrid();
}
void resizeGL( int width, int height ){
height = height?height:1;
glViewport( 0, 0, (GLint)width, (GLint)height );
// update projection matrix
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,.10f,200.0f);
// modeview matrix is simply identity
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
void paintGL(){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//set camera position using gluLookAt
glLoadIdentity();
gluLookAt(0.0f,0.0f,0.0f,0.0f,0.0f,-200.0f,0.0f,1.0f,0.0f);
}
void doCircle(double x, double y, double radius){
glEnable(GL_BLEND);
double y1=y+radius;
double x1=x;
glBegin(GL_LINE_STRIP);
for(double angle=0.0f;angle<=(2.0f*3.14159);angle+=0.01f){
double x2=x+(radius*(float)sin((double)angle));
double y2=y+(radius*(float)cos((double)angle));
glColor3f(1.0,1.0,1.0); //White
glVertex2d(x1,y1);
y1=y2;
x1=x2;
}
glEnd();
glDisable(GL_BLEND);
}
void drawRGrid(){
float xCirc = 0;
float yCirc = 0;
int numCircles = 5;
int threesixty = 360;
int numLines = 20;
//draws my circles
for (int i=0; i < numCircles;i++ ){
doCircle(1.0,1.0,i);
}
//draws my lines
for (int j=0; j < threesixty / numLines;j+= numLines){
// multiply by numCircles to get to extend to
// that length
drawLines(sin(j)*numCircles,sin(j)*numCircles);
}
}
void drawLines(float xCirc, float yCirc){
glBegin(GL_LINES);
glVertex2f(0,0);
glVertex2f(xCirc,yCirc);
glEnd();
}
};
Any help will be great appreciated! 任何帮助将非常感谢!
You have declared main()
as a member function. 您已将
main()
声明为成员函数。
The main()
function called when the application starts up needs to be a non-member function in the global namespace. 应用程序启动时调用的
main()
函数需要是全局命名空间中的非成员函数。
A good introductory C++ book would explain this. 一本好的C ++入门书将解释这一点。
You declared main
in class Solar
. 你在
Solar
宣布main
。 main
is supposed to be a free function, ie not contained within a class. main
应该是一个自由函数,即不包含在类中。
main
cannot be found because the function you wrote is called Solar::main
(in truth, it has a much funnier name). main
无法找到,因为你写的函数叫做Solar::main
(事实上,它有一个更有趣的名字)。 You need to move it below class Solar
. 你需要将它移到
class Solar
下面。 Then you probably want to change class Solar
into struct Solar
until you introduce member variables. 那么您可能希望将
class Solar
更改为struct Solar
直到您引入成员变量。 At last, you may want to rewrite main
to be 最后,您可能想要重写
main
extern "C" int main (int /* argc */, char *const * /* argv */) {
Solar solar;
solar.initializeGL();
//Stars Alpha = new Stars(5.0);
//Stars *Alpha = new Stars(5.0);
//Planets *Awe = new Planets(.6,2,30,"Awe",0.0,0.0,0.0);
solar.paintGL();
return 0;
}
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