SDL位面:分割错误

SDL blit surface: Segmentation fault

本文关键字：错误 分割 位面 SDL      更新时间：2023-10-16

每次我运行这个程序，我得到这样的错误:

段错误

testing.cpp 

#include <iostream>
#include <cstdint>
#include <SDL.h>
#include <SDL_image.h>
#include "Surface.h"
#include "Point2D.h"
int main() {
    if (SDL_Init(SDL_INIT_EVERYTHING) != 0) {
        std::cerr << "Can not init SDL" << std::endl;
        return -1;
    }
    SDL_Surface *scr = SDL_SetVideoMode(800, 600, 0, SDL_HWSURFACE | SDL_DOUBLEBUF);
    if ( scr == NULL ) {
        std::cerr << "Can not open window" << std::endl;
        return -1;
    }
    SDL_WM_SetCaption("Test Surface class", NULL);
    Surface screen;
    Surface image;
    screen.set(SDL_GetVideoSurface());
    if (image.load("./data/images/logo.png") == false) {
        std::cerr << "Can not open file" << std::endl;
        return -1;
    }
    bool run = true;
    uint32_t sticks = SDL_GetTicks();
    while(run) {
        if (screen.draw(image, Rectangle(0, 0, image.getWidth(), image.getHeight()), Point2D(0, 0)) == false) {
            std::cerr << "Can not draw to window" << std::endl;
            return -1;
        }
        if ((SDL_GetTicks() - sticks)/1000 > 5) {
            std::cerr << "End of time" << std::endl;
            run = false;
        }
        SDL_Flip(screen.sdlSurface());
    }
    std::cerr << "Done" << std::endl;
    SDL_Quit();
    return 0;
}

有类Surface

的源代码
#include "Surface.h"
#include "Color.h"
Surface::Surface() {
    this->surface = NULL;
}
Surface::~Surface() {
    SDL_FreeSurface(this->surface);
    this->surface = NULL;
}
bool Surface::draw(Surface source, Rectangle source_area, Point2D position) {
    SDL_Rect sr = source_area.sdlRect();
    SDL_Rect tr = {position.getX(), position.getY(), 0, 0};
    std::cout << sr.x << "," << sr.y << "," << sr.w << "," << sr.h << std::endl;
    std::cout << tr.x << "," << tr.y << "," << tr.w << "," << tr.h << std::endl;
    std::cout << source.sdlSurface() << std::endl;
    std::cout << this->surface << std::endl;
    // TR and SR are currently unused. Just for case of testing
    if (SDL_BlitSurface(source.sdlSurface(), NULL, this->surface, NULL) != 0) {
        return false;
    }
    return true;
}
bool Surface::fill(Color color, Rectangle area) {
    SDL_Rect tr = area.sdlRect();
    std::cout << tr.x << "," << tr.y << "," << tr.w << "," << tr.h << std::endl;
    std::cout << (int)color.sdlColor() << std::endl;
    if ( SDL_FillRect(this->surface, &tr, color.sdlColor()) != 0) {
        return false;
    }
    return true;
}
Rectangle Surface::getSize() {
    return Rectangle(0, 0, this->getWidth(), this->getHeight());
}
bool Surface::load(std::string file) {
    SDL_Surface *src = IMG_Load(file.c_str());
    if (src == NULL) {
        std::cout << "cyh" << std::endl;
        std::cout << IMG_GetError() << std::endl;
        return false;
    }
    this->surface = SDL_DisplayFormatAlpha(src);
    if (this->surface == NULL) {
        std::cout << "cyh1" << std::endl;
        std::cout << SDL_GetError() << std::endl;
        return false;
    }
    SDL_FreeSurface(src);
    src = NULL;
    return true;
}
void Surface::set(SDL_Surface *surface) {
    this->surface = surface;
}
void Surface::set(Surface surface) {
    this->surface = surface.sdlSurface();
}

问题可能出在绘制函数上。如果我改变这一行:

if (SDL_BlitSurface(source.sdlSurface(), NULL, this->surface, NULL) != 0) {

: 

if (SDL_BlitSurface(IMG_Load("./data/images/logo.png"), NULL, this->surface, NULL) != 0) {

一切似乎都很好。你能给我一个建议吗?问题出在哪里?

你违反了3的规则。

需要定义一个复制构造函数和一个复制赋值操作符才能正常工作。

当你将Surface传递给draw方法时，你是在复制它。因为你在Surface类(SDL_Surface*)中管理一个资源，你会有多个类的实例指向同一个Surface，所以当析构函数被调用时，你会不止一次地释放同一个SDL_Surface*。

编辑:我建议通过const引用传递你的参数。当你想绘制Surface对象时，你不需要复制它们。

: 

bool Surface::draw(Surface source, Rectangle source_area, Point2D position);

会变成这样:

bool Surface::draw(const Surface &source, const Rectangle &source_area, const Point2D &position);

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