[postgis-tickets] [PostGIS] #4990: getfacecontainingpoint fails on i386

[PostGIS]

#4990: getfacecontainingpoint fails on i386
-----------------------------+---------------------------
  Reporter:  Bas Couwenberg  |      Owner:  strk
      Type:  defect          |     Status:  new
  Priority:  medium          |  Milestone:  PostGIS 3.2.0
 Component:  topology        |    Version:  master
Resolution:                  |   Keywords:
-----------------------------+---------------------------

Comment (by strk):

 I've handled to get debugging output of a failing run by moving the DEBUG
 to *after* the less-than comparison. This means that the less-then
 comparison works differently IF the {{{ dist_sqr }}} is printed in a debug
 or not. This very much points to some compiler optimization, using more
 bits in some cases for computations. Anyway, the debug shows this:

 {{{
 DEBUG:  [lwgeom_topo.c:lwt_GetFaceContainingPoint:7092] Closest edge 26:
 LINESTRING(4 31,7 31,7 34,4 34,4 31)
 DEBUG:  [lwgeom_topo.c:lwt_GetFaceContainingPoint:7098] Shortest line to
 closest edge 26: LINESTRING(7 31,7.1 31)
 DEBUG:  [lwgeom_topo.c:lwt_GetFaceContainingPoint:7104] Closest point on
 closest edge: POINT(7 31)
 DEBUG:  [lwgeom_topo.c:lwt_GetFaceContainingPoint:7210] Closest point is
 NOT a node
 DEBUG:  [ptarray.c:ptarray_closest_segment_2d:1316] Sqr distance from seg
 0: 0.009999999999999929084504302
 DEBUG:  [ptarray.c:ptarray_closest_segment_2d:1316] Sqr distance from seg
 1: 0.009999999999999929084504302
 DEBUG:  [lwgeom_topo.c:lwt_GetFaceContainingPoint:7237] Closest segment on
 edge 26 is 1
 }}}

 That's a 25 significant digit figure, printed as all EQUAL digit, and
 still finding the second number being < than the first one ! Maybe this is
 a place to use DBL_EPSILON macro, although I don't feel like we should be
 doing such things :(

 Paul: is DBL_EPSILON macro yours ?

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/4990#comment:26>
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