SDL_ttf文本渲染程序执行SDL_FreeSurface时触发访问冲突错误求助

问题代码 #

#include <stdio.h>
#include <SDL.h>
#include <SDL_ttf.h>
#include <stdbool.h>

SDL_Renderer* renderer;
TTF_Font* font = NULL;

int main()
{
    SDL_Init(SDL_INIT_VIDEO);

    SDL_Window* win = SDL_CreateWindow("Title", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, SDL_WINDOW_SHOWN);
    renderer = SDL_CreateRenderer(win, -1, SDL_RENDERER_PRESENTVSYNC);
    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 0);

    // Font
    if (TTF_Init() < 0)
    {
        printf("Failed to initialize TTF!\n");
    }
    font = TTF_OpenFont("arial.ttf", 12);
    if (!font)
    {
        printf("Failed to load font!\n");
    }

    bool quit = false;
    SDL_Event e;
    while (!quit)
    {
        while (SDL_PollEvent(&e) != 0)
        {
            if (e.type == SDL_KEYDOWN && e.key.keysym.sym == SDLK_q)
            {
                quit = true;
            }
        }
        SDL_RenderClear(renderer);

        SDL_SetRenderDrawColor(renderer, 255, 0, 0, 0);
        SDL_Rect rect = { 200, 40, 400, 400 };
        SDL_RenderDrawRect(renderer, &rect);

        SDL_Color textColor = { 0, 0, 0 };
        SDL_Surface* textSurface = TTF_RenderText_Solid(font, "HELLO", textColor);
        if (textSurface == NULL)
        {
            printf("Error %s\n", SDL_GetError());
        }
        else
        {
            SDL_Texture* mTexture = SDL_CreateTextureFromSurface(renderer, textSurface);
            if (mTexture == NULL) 
            {
                printf("Error %s\n", SDL_GetError());
            }
            else
            {
                SDL_Rect rectSrc = { 0, 0, textSurface->w, textSurface->h };
                SDL_Rect rectDes = { 25, 25, textSurface->w, textSurface->h };
                SDL_RenderCopy(renderer, mTexture, &rectSrc, &rectDes);

                SDL_DestroyTexture(mTexture);
            }
            SDL_FreeSurface(textSurface);
        }

        SDL_SetRenderDrawColor(renderer, 255, 255, 255, 0);
        SDL_RenderPresent(renderer);
    }

    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(win);
    TTF_Quit();
    SDL_Quit();

    return 0;
}

错误现象 #

执行SDL_FreeSurface(textSurface);时触发访问冲突：

Exception thrown at 0x000000005FA48159 (SDL2.dll) in TestSDL.exe: 0xC0000005: Access violation reading location 0xFFFFFFFFFFFFFFFF.

错误发生时textSurface的状态：

触发原因 #

核心问题在于字体加载失败后程序未终止，导致后续使用无效指针调用TTF渲染函数：

1. 当TTF_OpenFont("arial.ttf", 12)加载失败时，font被设为NULL，但代码仅打印错误信息，未退出程序或终止渲染逻辑。
2. 主循环中使用NULL的font调用TTF_RenderText_Solid时，SDL_ttf并未返回预期的NULL，而是返回了非法指针0xFFFFFFFF（即-1）。
3. 代码中的if (textSurface == NULL)判断无法识别该非法指针，会进入else分支执行后续逻辑，最终调用SDL_FreeSurface释放非法指针，触发访问冲突。

内容的提问来源于stack exchange，提问作者Kazgaa