[GRASS-dev] [GRASS GIS] #3564: Inconsistent results from qsort callback in g.mkfontcap

[GRASS GIS]

#3564: Inconsistent results from qsort callback in g.mkfontcap
----------------------+----------------------------
  Reporter:  yugr     |      Owner:  grass-dev@…
      Type:  defect   |     Status:  new
  Priority:  normal   |  Milestone:  7.6.0
 Component:  Default  |    Version:  7.4.0
Resolution:           |   Keywords:  qsort callback
       CPU:  All      |   Platform:  All
----------------------+----------------------------
Changes (by mmetz):

 * keywords:   => qsort callback
 * milestone:   => 7.6.0


Comment:

 Replying to [ticket:3564 yugr]:
 > Hi,
 >
 > qsort callback compare_fonts in g.mkfontcap may return invalid result
 when arguments are swapped. Such bugs may causes inconsistent order or
 even crashes in some qsort implementations
 (​https://bugzilla.samba.org/show_bug.cgi?id=3959).
 >
 > The issue has been detected when running standard testsuite under
 SortChecker? (​https://github.com/yugr/sortcheck):
 >
 >   g.mkfontcap[15109]: qsort: comparison function is not symmetric
 (comparison function 0x4023c0 (/build/grass-7.0.3/dist.x86_64-pc-linux-
 gnu/bin/g.mkfontcap+0x4023c0), called from 0x4017a8
 (/build/grass-7.0.3/dist.x86_64-pc-linux-gnu/bin/g.mkfontcap+0x4017a8),
 cmdline is "/build/grass-7.0.3/dist.x86_64-pc-linux-gnu/bin/g.mkfontcap
 -s")
 >
 > Problem is in lines
 >     if (aa->type != bb->type)
 >         return (aa->type > bb->type);
 > which should be replaced with something like
 >     if (aa->type != bb->type)
 >         return (aa->type > bb->type) ? 1 : -1;

 Fixed in trunk r72727.
 >
 > As a side note, many qsort callbacks in Grass are vulnerable to integer
 overflows e.g. cmp_edge in ./lib/vector/neta/spanningtree.c:
 >
 >     return ((edge_cost_pair *) pa)->cost - ((edge_cost_pair *)
 pb)->cost;
 >

 Fixed in trunk r72728.

 > or longcmp in ./raster/r.kappa/prt_mat.c:
 >
 >     return (*a - *b);

 Fixed in trunk r72729.
 >
 > and many many others.

 If you already have a list of these many other problems, can you provide
 such a list? That would be very helpful.

-- 
Ticket URL: <https://trac.osgeo.org/grass/ticket/3564#comment:1>
GRASS GIS <https://grass.osgeo.org>