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Author Topic: Empty image semantics  (Read 1735 times)

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Nexus

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Empty image semantics
« on: December 26, 2010, 03:04:33 pm »
Although this is rather a theoretical problem, I want to inform you about some observations I've made. The following code fails with a STL debug assertion (VS 2010):
Code: [Select]
#include <SFML/Graphics/Image.hpp>
int main()
{
sf::Image image;
image.SaveToFile("image.bmp");
}

The problem is the statement &pixels[0] in ImageLoader.cpp. As far as I know, if you access the 0th element of an empty std::vector, you evoke undefined behaviour.

There are a few other places (also in Image.cpp) where the access is unchecked. In some of them, you could handle it like in Image::CreateMaskFromColor():
Code: [Select]
if (myPixels.empty())
        return;

But I don't know if there is a convention how to represent empty image files. Anyway, you should probably make the semantics clearer or explicitly forbid some operations on singular sf::Image instances.
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Laurent

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Empty image semantics
« Reply #1 on: December 26, 2010, 04:04:58 pm »
This is absolutely true. It's a shame that I left so many undefined behaviours in sf::Image :P

I reviewed all the functions and made sure that the behaviour is always well-defined and robust.

Thanks :)
Laurent Gomila - SFML developer

Nexus

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Empty image semantics
« Reply #2 on: December 27, 2010, 05:11:03 pm »
Thank you :)
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