cerr不能打印浮点变量

cerr不能打印浮点变量

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问题描述

我正在编写一个程序,它应该使用矩阵操作,并使用OpenGL框架来绘制它们。老实说,这只是为了练习。无论如何,我试图编译它,当然,它没有运行良好。插入尽可能多的日志记录,我发现我的 std :: cerr 不能打印 float 值。我真的不知道如何可能停止工作。我对我的小代码做了一些深入的研究,如用它们的值替换变量,使用相同的函数编写外部程序等;发现更令人难以置信的事情,这绝对没有理由这样。

有用的细节



OS X 10.9。
除了由 #pragma once 引起的预编译之外,不会发生预编译的错误。



编译器

Apple LLVM版本6.0(clang-600.0.57)(基于LLVM 3.5svn)。



g ++ -std = c ++ 11 -framework OpenGL -framework GLUT



main.cpp



  #include< GLUT / glut.h> 

#include< cstdlib>

#includeWindow.hpp

Window * black_screen;

void Display(){black_screen-> Display(); }
void Reshape(int NEW_WIDTH,int NEW_HEIGHT){black_screen-> Reshape(NEW_WIDTH,NEW_HEIGHT); }
void Keyboard(unsigned char key,int x,int y){black_screen-> Keyboard(key,x,y); }
void Special(int key,int x,int y){black_screen-> Special(key,x,y); }

int main(int argc,char ** argv){
glutInit(& argc,argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);

窗口* black_screen =新窗口(800,800);

glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);

glutDisplayFunc(Display);
glutReshapeFunc(Reshape);
glutKeyboardFunc(Keyboard);
glutSpecialFunc(Special);

black_screen-> AddMatrix(Matrix(5));

Display();

glutMainLoop();
}



WINDOW.hpp



  #pragma once 

#include< GLUT / glut.h>
#include< cstdlib>
#include< iostream>
#include< string>

#includeMatrix.hpp

class Window {
std :: vector< Matrix> matrices_;
浮动WIDTH_,HEIGHT_,
SIZE_X_,SIZE_Y_;
const char * NAME_;
public:
Window(const float WIDTH,const float HEIGHT);
private:
void类型(const float x,const float y,const char * string)const;
public:
void AddMatrix(const Matrix& A);
void Write(const std :: string& message);
void Display();
void Reshape(int NEW_WIDTH,int NEW_HEIGHT);
void Keyboard(unsigned char key,int x,int y);
void Special(int key,int x,int y);
};



WINDOW.cpp



  // --- THIS IS CONSTRUCTOR --- --- --- --- --- 

Window :: Window(const float WIDTH,const float HEIGHT) :
WIDTH_(WIDTH),HEIGHT_(HEIGHT),
SIZE_X_(800),SIZE_Y_(800),
NAME _(MATRIX){
...
}


// ---这是显示功能从MAIN :: Display()---

调用void Window :: Display(){
glLoadIdentity(); Write(glLoadIdentity(););
glClear(GL_COLOR_BUFFER_BIT); Write(glClear(GL_COLOR_BUFFER_BIT););
glMatrixMode(GL_PROJECTION); Write(glMatrixMode(GL_PROJECTION););
Write(\tNOW i WILL TRY TO OUTPUT HEIGHT_:);
std :: cerr<< HEIGHT_<< std :: endl;
glOrtho(0,WIDTH_,0,HEIGHT_,1,-1); // Write(glOrtho(0,WIDTH_,0,HEIGHT_,1,-1););
...
}



输出



  [glutInitWindowSize(SIZE_X_,SIZE_Y_); :
[SIZE_X_ 800.000000
[SIZE_Y_ 800.000000
[glutCreateWindow(NAME_); :
[NAME_ MATRIX
[glLoadIdentity();
[glClear(GL_COLOR_BUFFER_BIT);
[glMatrixMode(GL_PROJECTION);
[现在我将尝试输出HEIGHT_:
make:*** [run]分段错误:11


解决方案

您不会在已发布的代码中显示此信息,但您似乎对 black_screen ,一个全局变量和一个 main 函数。 main 中的一个已经正确初始化,但是全局变量是一个坏指针。分段错误是通过取消引用错误指针的未定义行为的结果。


I am writing a program that is supposed to operate with matrices and to use OpenGL framework for drawing them. Honestly, it's just for practice. Anyway, I tried to compile it and, of course, it didn't run well. Inserting as many logging as I could, I found out that my std::cerr can't print float values. I really got no idea how that may stop working. I have made some deep researches on my little code like replacing variables with their values, coding external programs using same functions and so on; and found even more unbelievable thing that there's absolutely no reason for this.

Useful details

OS X 10.9.No bugs regarding to precompilation may occur other than ones caused by #pragma once.

Compiler

Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn).

g++ -std=c++11 -framework OpenGL -framework GLUT

main.cpp

#include <GLUT/glut.h>

#include <cstdlib>

#include "Window.hpp"

Window *black_screen;

void Display    ()                                      {   black_screen->Display   ();                         }
void Reshape    (int NEW_WIDTH, int NEW_HEIGHT)         {   black_screen->Reshape   (NEW_WIDTH, NEW_HEIGHT);    }
void Keyboard   (unsigned char key, int x, int y)       {   black_screen->Keyboard  (key, x, y);                }
void Special    (int key, int x, int y)                 {   black_screen->Special   (key, x, y);                }

int main(int argc, char **argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);

    Window *black_screen = new Window(800, 800);

    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    glutDisplayFunc     (   Display     );
    glutReshapeFunc     (   Reshape     );
    glutKeyboardFunc    (   Keyboard    );
    glutSpecialFunc     (   Special     );

    black_screen->AddMatrix(Matrix(5));

    Display();

    glutMainLoop();
}

WINDOW.hpp

#pragma once

#include <GLUT/glut.h>
#include <cstdlib>
#include <iostream>
#include <string>

#include "Matrix.hpp"

class Window {
    std::vector <Matrix> matrices_;
    float WIDTH_, HEIGHT_,
          SIZE_X_, SIZE_Y_;
    const char *NAME_;
public:
    Window      (const float WIDTH, const float HEIGHT);
private:
    void Type   (const float x, const float y, const char *string) const;
public:
    void AddMatrix  (const Matrix &A);
    void Write  (const std::string &message);
    void Display    ();
    void Reshape    (int NEW_WIDTH, int NEW_HEIGHT);
    void Keyboard   (unsigned char key, int x, int y);
    void Special    (int key, int x, int y);
};

WINDOW.cpp

// ---  THIS IS CONSTRUCTOR --- --- --- --- ---

Window::Window          (const float WIDTH, const float HEIGHT) :
    WIDTH_(WIDTH), HEIGHT_(HEIGHT),
    SIZE_X_(800), SIZE_Y_(800),
    NAME_("MATRIX") {
        ...
}


// ---  THIS IS DISPLAY FUNCTION CALLED FROM MAIN::Display()    ---

void    Window::Display     () {
    glLoadIdentity();                       Write("glLoadIdentity();");
    glClear(GL_COLOR_BUFFER_BIT);                   Write("glClear(GL_COLOR_BUFFER_BIT);");
    glMatrixMode(GL_PROJECTION);                    Write("glMatrixMode(GL_PROJECTION);");
    Write("\tNOW i WILL TRY TO OUTPUT HEIGHT_ :");
    std::cerr << HEIGHT_ << std::endl;
    glOrtho(0, WIDTH_, 0, HEIGHT_, 1, -1);              //Write("glOrtho(0, WIDTH_, 0, HEIGHT_, 1, -1);");
    ...
}

output

[   glutInitWindowSize(SIZE_X_, SIZE_Y_); :
[       SIZE_X_ 800.000000
[       SIZE_Y_ 800.000000
[   glutCreateWindow(NAME_); :
[       NAME_   MATRIX
[   glLoadIdentity();
[   glClear(GL_COLOR_BUFFER_BIT);
[   glMatrixMode(GL_PROJECTION);
[       NOW i WILL TRY TO OUTPUT HEIGHT_ :
make: *** [run] Segmentation fault: 11
解决方案

You don't show this in the code posted, but it appears you have two different definitions for black_screen, one global and one inside the main function. The one inside main has been initialized properly, but the global one is a bad pointer. The segmentation fault is the result of undefined behavior from dereferencing the bad pointer.

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09-02 15:32