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Re: [ft-devel] Dynamic limits for TrueType bytecode execution
From: |
Marek Kasik |
Subject: |
Re: [ft-devel] Dynamic limits for TrueType bytecode execution |
Date: |
Tue, 30 May 2017 12:56:27 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 |
Hi,
On 09/27/2016 09:15 AM, Werner LEMBERG wrote:
>
> From the CHANGES file:
>
> - Some limits for TrueType bytecode execution have been tightened
> to speed up FreeType's handling of malformed fonts, in
> particular to quickly abort endless loops.
>
> - The number of twilight points can no longer be set to an
> arbitrarily large value.
>
> - The total number of jump opcode instructions (like JMPR) with
> negative arguments is dynamically restricted; the same holds
> for the total number of iterations in LOOPCALL opcodes.
>
> The dynamic limits are based on the number of points in a glyph
> and the number of CVT entries. Please report if you encounter a
> font where the selected values are not adequate.
>
> So: Please test and report :-)
a problematic font was encountered by reporter of this downstream bug:
https://bugzilla.redhat.com/show_bug.cgi?id=1456585.
The font there is Padauk-Bold.ttf (version 3.002 (it works with current
upstream)). It has exc->cvtSize == 35 so the exc->loopcall_counter_max
== 350 but exc->loopcall_counter == 523.
Do you consider this a problem of the font (which is fixed in current
master of the font - but it doesn't seem that they targeted this issue
specifically) or something because of which the limits should be adjusted?
> Werner
Regards
Marek
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