[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:
Component:  Default  |    Version:  7.4.0
 Keywords:           |        CPU:  All
 Platform:  All      |
---------------------+-------------------------
 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;

 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;

 or longcmp in ./raster/r.kappa/prt_mat.c:

     return (*a - *b);

 and many many others.

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