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Re: Warning in svg_load_image
From: |
Eli Zaretskii |
Subject: |
Re: Warning in svg_load_image |
Date: |
Thu, 24 Feb 2022 08:47:43 +0200 |
> From: Michael Welsh Duggan <mwd@md5i.com>
> Cc: Michael Welsh Duggan <mwd@md5i.com>, luangruo@yahoo.com,
> emacs-devel@gnu.org
> Date: Wed, 23 Feb 2022 16:58:59 -0500
>
> > If the compiler doesn't understand that the value is being limited to
> > a maximum of 5 digits, then it shouldn't attempt to emit such
> > "helpful" warnings.
>
> Is it being limited? What is limiting it? "%5.0f" will not limit it's
> size; it will only limit its minimum size, unless I am misunderstanding
> the printf specs.
That's not the limitation I had in mind, I meant the limitation of the
values printed with those formats:
> if (buffer_size <= snprintf (wrapped_contents, buffer_size, wrapper,
> foreground & 0xFFFFFF, width, height,
> - viewbox_width, viewbox_height,
> + /* Sanitize the viewBox dimensions. */
> + min (max (viewbox_width, 1.), 10000.),
> + min (max (viewbox_height, 1.), 10000.),
> background & 0xFFFFFF,
> SSDATA (encoded_contents)))
Here, it should be clear to the compiler that:
. the #%06X formats cannot produce more than 6 characters each
. the %d formats cannot produce more than 12 characters each
. the %5.0f formats cannot produce more than 5 characters each
> >> The principled way to solve this would be to call the snprintf twice,
> >> the first time with a zero-sized buffer, and then to use the return
> >> value to allocate the actual buffer. This is a pessimisation, but I
> >> don't know if it's a bad one (it depends on how frequently this code
> >> would be called.
> >
> > This is madness. I'd rather we used a pragma to disable that
> > particular warning around this part of the code than jump through
> > hoops because the compiler is too stupid to understand the code it
> > warns about.
>
> Another possible option: you may be able to work around this by
> declaring buffer_size to be volatile.
That'd slow down the code in production, which is not a good idea.
- Re: Warning in svg_load_image, (continued)
- Re: Warning in svg_load_image, Eli Zaretskii, 2022/02/21
- Re: Warning in svg_load_image, Po Lu, 2022/02/21
- Re: Warning in svg_load_image, Eli Zaretskii, 2022/02/21
- Re: Warning in svg_load_image, Po Lu, 2022/02/21
- Re: Warning in svg_load_image, Eli Zaretskii, 2022/02/22
- Re: Warning in svg_load_image, Andreas Schwab, 2022/02/22
- Re: Warning in svg_load_image, Po Lu, 2022/02/22
- Re: Warning in svg_load_image, Michael Welsh Duggan, 2022/02/23
- Re: Warning in svg_load_image, Eli Zaretskii, 2022/02/23
- Re: Warning in svg_load_image, Michael Welsh Duggan, 2022/02/23
- Re: Warning in svg_load_image,
Eli Zaretskii <=
- Re: Warning in svg_load_image, Andreas Schwab, 2022/02/23
- Re: Warning in svg_load_image, Eli Zaretskii, 2022/02/24
- Message not available
- Re: Warning in svg_load_image, Po Lu, 2022/02/23