Re: [glennrp/libpng] Undefined behaviour in pngutil.c (#149)

I've pushed a change to the GIT repositories to
change png_ptr->options from a png_byte to a
png_uint_32.

Glenn

On Mon, Jan 2, 2017 at 7:40 PM, Glenn Randers-Pehrson <[email protected]>
wrote:

> This bug report is correct.  I wasn't paying attention, did not
> realize thought the "options" was limited to four (there's a
> comment about that but I didn't see it).
>
> We could recover the unused MIPS option, I suppose.
> and/or rewrite the options mechanism to use
> a png_uint_32 for png_ptr->opitons which would
> allow a total of 16 options.
>
> No one has even tried the MIPS feature as far as I can
> tell, and I'm ready to remove it.  It isn't in libpng17.
>
> Glenn
>
> ---------- Forwarded message ----------
> From: irwir <notifications-9UaJU3cA/F/[email protected]>
> Date: Mon, Jan 2, 2017 at 7:22 PM
> Subject: [glennrp/libpng] Undefined behaviour in pngutil.c (#149)
> To: glennrp/libpng <[email protected]>
> Cc: Subscribed <[email protected]>
>
>
> Line 423 in libpng16 pngutil.c is
> if (((png_ptr->options >> PNG_IGNORE_ADLER32) & 3) == PNG_OPTION_ON)
>
> png_ptr->options is png_byte and has 8 bits
> PNG_IGNORE_ADLER32 equals 8
> C/C++ standards claim that shift by the number of available bits (or more)
> is an undefined behaviour.
>
> —
> You are receiving this because you are subscribed to this thread.
> Reply to this email directly, view it on GitHub
> <https://github.com/glennrp/libpng/issues/149>, or mute the thread
> <https://github.com/notifications/unsubscribe-auth/ABe25shZH-f9fjyJSDYoOZCeKmYfD_uAks5rOZSvgaJpZM4LZRLw>
> .
>
>

------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most 
engaging tech sites, SlashDot.org! http://sdm.link/slashdot

_______________________________________________
png-mng-implement mailing list
png-mng-implement-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
https://lists.sourceforge.net/lists/listinfo/png-mng-implement