libpng/ANNOUNCE

Libpng 1.6.24beta02 - June 20, 2016

This is not intended to be a public release.  It will be replaced
within a few weeks by a public version or by another test version.

Files available for download:

Source files with LF line endings (for Unix/Linux) and with a
"configure" script

   1.6.24beta02.tar.xz (LZMA-compressed, recommended)
   1.6.24beta02.tar.gz

Source files with CRLF line endings (for Windows), without the
"configure" script

   lp1624b02.7z  (LZMA-compressed, recommended)
   lp1624b02.zip

Other information:

   1.6.24beta02-README.txt
   1.6.24beta02-LICENSE.txt
   libpng-1.6.24beta02-*.asc (armored detached GPG signatures)

Changes since the last public release (1.6.23):

Version 1.6.24beta01 [June 11, 2016]
  Avoid potential overflow of the PNG_IMAGE_SIZE macro.  This macro
    is not used within libpng, but is used in some of the examples.

Version 1.6.24beta02 [June 20, 2016]
  Correct filter heuristic overflow handling. This was broken when the
    write filter code was moved out-of-line; if there is a single filter and
    the heuristic sum overflows the calculation of the filtered line is not
    completed.  In versions prior to 1.6 the code was duplicated in-line
    and the check not performed, so the filter operation completed; however,
    in the multi-filter case where the sum is performed the 'none' filter would
    be selected if all the sums overflowed, even if it wasn't in the filter
    list.  The fix to the first problem is simply to provide PNG_SIZE_MAX as
    the current lmins sum value; this means the sum can never exceed it and
    overflows silently.  A reasonable compiler that does choose to inline
    the code will simply eliminate the sum check.
  The fix to the second problem is to use high precision arithmetic (this is
    implemented in 1.7), however a simple safe fix here is to chose the lowest
    numbered filter in the list from png_set_filter (this only works if the
    first problem is also fixed) (John Bowler).
  Use a more efficient absolute value calculation on SSE2 (Matthieu Darbois).

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Glenn R-P