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Fix "out of bounds" undefined behavior #16975

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Merged
merged 1 commit into from
Apr 30, 2020
Merged

Fix "out of bounds" undefined behavior #16975

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11 changes: 5 additions & 6 deletions extern/agg24-svn/include/agg_pixfmt_gray.h
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Original file line number Diff line number Diff line change
Expand Up @@ -136,14 +136,13 @@ namespace agg
typedef typename color_type::calc_type calc_type;
enum
{
num_components = 1,
pix_width = sizeof(value_type) * Step,
pix_step = Step,
pix_offset = Offset,
};
struct pixel_type
{
value_type c[num_components];
value_type c[pix_step];

void set(value_type v)
{
Expand All @@ -167,22 +166,22 @@ namespace agg

pixel_type* next()
{
return (pixel_type*)(c + pix_step);
return this + 1;
}

const pixel_type* next() const
{
return (const pixel_type*)(c + pix_step);
return this + 1;
}

pixel_type* advance(int n)
{
return (pixel_type*)(c + n * pix_step);
return this + n;
}

const pixel_type* advance(int n) const
{
return (const pixel_type*)(c + n * pix_step);
return this + n;
}
};

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11 changes: 5 additions & 6 deletions extern/agg24-svn/include/agg_pixfmt_rgb.h
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Original file line number Diff line number Diff line change
Expand Up @@ -192,14 +192,13 @@ namespace agg
typedef typename color_type::calc_type calc_type;
enum
{
num_components = 3,
pix_step = Step,
pix_offset = Offset,
pix_width = sizeof(value_type) * pix_step
};
struct pixel_type
{
value_type c[num_components];
value_type c[pix_step];

void set(value_type r, value_type g, value_type b)
{
Expand Down Expand Up @@ -230,22 +229,22 @@ namespace agg

pixel_type* next()
{
return (pixel_type*)(c + pix_step);
return this + 1;
}

const pixel_type* next() const
{
return (const pixel_type*)(c + pix_step);
return this + 1;
}

pixel_type* advance(int n)
{
return (pixel_type*)(c + n * pix_step);
return this + n;
}

const pixel_type* advance(int n) const
{
return (const pixel_type*)(c + n * pix_step);
return this + n;
}
};

Expand Down
22 changes: 10 additions & 12 deletions extern/agg24-svn/include/agg_pixfmt_rgba.h
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Expand Up @@ -1515,13 +1515,12 @@ namespace agg
typedef typename color_type::calc_type calc_type;
enum
{
num_components = 4,
pix_step = 4,
pix_width = sizeof(value_type) * pix_step,
};
struct pixel_type
{
value_type c[num_components];
value_type c[pix_step];
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I don't think this should change, as it makes the rgba file inconsistent with the rgb one, and semantically these are different things.

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@vitalybuka vitalybuka Apr 3, 2020 •
edited
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What if we change them as well? Looks like this way code is simpler and compliant.
Then num_components is not used anywhere, but I can return it back if you like.
PTAL

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@tkoeppe tkoeppe Apr 27, 2020 •
edited
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@QuLogic : Has this point been resolved? (I don't have any opinion either way, but I wanted to make sure this isn't a blocker.)

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(For what it's worth, if it is easier to land this overall fix without chaning the bounds here, I'd welcome that as a simpler first step; the deduplication of these two redundant enumerators could be a separate PR.)

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I like as small as possible patches as well. Still here to use "this + 1" we need array size to be the "pix_step" not "num_components". Then num_components is unused. So the best I can do is moving lines with "- num_components = ..." into a separate PR.

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Not sure who you're tagging there; as you can see I've already approved.

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@vitalybuka: Ah of course, Step could be not 1... say, is the current code correct when Step is not 1? In that case the current code's next would skip over some array elements, right?


void set(value_type r, value_type g, value_type b, value_type a)
{
Expand Down Expand Up @@ -1555,22 +1554,22 @@ namespace agg

pixel_type* next()
{
return (pixel_type*)(c + pix_step);
return this + 1;
}

const pixel_type* next() const
{
return (const pixel_type*)(c + pix_step);
return this + 1;
}

pixel_type* advance(int n)
{
return (pixel_type*)(c + n * pix_step);
return this + n;
}

const pixel_type* advance(int n) const
{
return (const pixel_type*)(c + n * pix_step);
return this + n;
}
};

Expand Down Expand Up @@ -2193,13 +2192,12 @@ namespace agg
typedef typename color_type::calc_type calc_type;
enum
{
num_components = 4,
pix_step = 4,
pix_width = sizeof(value_type) * pix_step,
};
struct pixel_type
{
value_type c[num_components];
value_type c[pix_step];

void set(value_type r, value_type g, value_type b, value_type a)
{
Expand Down Expand Up @@ -2233,22 +2231,22 @@ namespace agg

pixel_type* next()
{
return (pixel_type*)(c + pix_step);
return this + 1;
}

const pixel_type* next() const
{
return (const pixel_type*)(c + pix_step);
return this + 1;
}

pixel_type* advance(int n)
{
return (pixel_type*)(c + n * pix_step);
return this + n;
}

const pixel_type* advance(int n) const
{
return (const pixel_type*)(c + n * pix_step);
return this + n;
}
};

Expand Down