Question

I’m trying to access the data that I previously allocated with the calloc method through a shared_ptr. For some reason I can’t access it (keeps on crashing with EXC_BAD_ACCESS) on glTexImage2D (last line of my code snippets).

My util method to load the data:

shared_ptr<ImageData> IOSFileSystem::loadImageFile(string path) const
{
    // Result
    shared_ptr<ImageData> result = shared_ptr<ImageData>();

    ...

    // Check if file exists
    if([[NSFileManager defaultManager] fileExistsAtPath:fullPath isDirectory:NO])
    {
        ...

        GLubyte *spriteData = (GLubyte*) calloc(width * height * 4, sizeof(GLubyte));

        ...

        // Put result in shared ptr
        shared_ptr<GLubyte> spriteDataPtr = shared_ptr<GLubyte>(spriteData);
        result = shared_ptr<ImageData>(new ImageData(path, width, height, spriteDataPtr));
    }
    else
    {
        cout << "IOSFileSystem::loadImageFile -> File does not exist at path.\nPath: " + path;
        exit(1);
    }

    return result;
}

Header for ImageData:

class ImageData
{
public:
    ImageData(string path, int width, int height, shared_ptr<GLubyte> data);
    ~ImageData();

    string getPath() const;

    int getWidth() const;
    int getHeight() const;

    shared_ptr<GLubyte> getData() const;

private:
    string path;

    int width;
    int height;

    shared_ptr<GLubyte> data;
};

File that calls the util class:

void TextureMaterial::load()
{
    shared_ptr<IFileSystem> fileSystem = ServiceLocator::getFileSystem();
    shared_ptr<ImageData> imageData = fileSystem->loadImageFile(path);

    this->bind(imageData);
}



void TextureMaterial::bind(shared_ptr<ImageData> data)
{
    // Pointer to pixel data
    shared_ptr<GLubyte> pixelData = data->getData();

    ...

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, data->getWidth(), data->getHeight(), 0, GL_RGBA, GL_UNSIGNED_BYTE, &pixelData);
}

Just for the record: if I throw out all shared_ptr’s I’m able to access the data. Signature for glTexImage2D:

void glTexImage2D(GLenum target, GLint level, GLint internalFormat, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, const GLvoid *data);

Additional question: normally you have to free(spriteData) but since I gave the data to a shared_ptr, will the data be free’d when the shared_ptr is removed?

Answer 1

I think this is your problem:

..., &pixelData);

You are taking an address of a local variable (of type shared_ptr<GLubyte>), which is silently cast to void*, instead of getting the pointer from it. Replace it with:

..., pixelData.get());