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Fix contrib/seg to be more wary of long input numbers.

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seg stores the number of significant digits in an input number
in a "char" field.  If char is signed, and the input is more than
127 digits long, the count can read out as negative causing
seg_out() to print garbage (or, if you're really unlucky,
even crash).

To fix, clamp the digit count to be not more than FLT_DIG.
(In theory this loses some information about what the original
input was, but it doesn't seem like useful information; it would
not survive dump/restore in any case.)

Also, in case there are stored values of the seg type containing
bad data, add a clamp in seg_out's restore() subroutine.

Per bug #17725 from Robins Tharakan.  It's been like this
forever, so back-patch to all supported branches.

Discussion: https://postgr.es/m/17725-0a09313b67fbe86e@postgresql.org
This commit is contained in:
Tom Lane
2022-12-21 17:51:50 -05:00
parent 33dd895ef3
commit 701c881f78
4 changed files with 33 additions and 7 deletions
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3
contrib/seg/sql/seg.sql
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@ -60,6 +60,9 @@ SELECT '3.400e5'::seg AS seg;
-- Digits truncated
SELECT '12.34567890123456'::seg AS seg;
-- Same, with a very long input
SELECT '12.3456789012345600000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'::seg AS seg;
-- Numbers with certainty indicators
SELECT '~6.5'::seg AS seg;
SELECT '<6.5'::seg AS seg;