[GRASS-dev] R: [GRASS-windows] WinGRASS: Test Build on Vista

[Benjamin Ducke]

So you agree that it may be worse trying to fix those
mem allocation issues to get r.los to work on Win32?

Ben

Glynn Clements wrote:
> Benjamin Ducke wrote:
> 
>> Actually, r.los seems to have faulty mem management on all platforms.
>> If I valgrind the module, I get:
>>
>> ==20182==    at 0x804AB15: hidden_point_elimination (pts_elim.c:105)
>> ==20182==    by 0x8049D74: main (main.c:303)
>> ==20182==  Address 0x4691CB8 is 24 bytes inside a block of size 32 free'd
>> ==20182==    at 0x402237F: free (vg_replace_malloc.c:233)
>> ==20182==    by 0x403767C: G_free (alloc.c:126)
>> ==20182==    by 0x8049673: delete (delete.c:39)
>> ==20182==    by 0x804AB14: hidden_point_elimination (pts_elim.c:189)
>> ==20182==    by 0x8049D74: main (main.c:303)
>>   100%
>> ==20182==
>> ==20182== Conditional jump or move depends on uninitialised value(s)
>> ==20182==    at 0x40A6CB2: (within /usr/lib/libz.so.1.2.3.3)
>> ==20182==    by 0x40A7E5F: deflate (in /usr/lib/libz.so.1.2.3.3)
>> ==20182==    by 0x40463A7: G_zlib_compress (flate.c:359)
>> ==20182==    by 0x4046551: G_zlib_write (flate.c:224)
>> ==20182==    by 0x405D54F: G__write_data_compressed (put_row.c:337)
>> ==20182==    by 0x405DE89: put_raster_row (put_row.c:477)
>> ==20182==    by 0x804A007: main (main.c:351)
>> ==20182==
>>
>> ... and a dozen more like that. Not a good sign really.
>>
>> My guess is that whether r.los crashes or not is simply due to
>> how relaxed the OS's memory allocation scheme is. Some systems
>> are more forgiving for the sake of better performance. I guess
>> that XP is more on the strict side and thus kills the module,
>> while Linux and Vista let you get away with it.
> 
> It's more likely to be plain luck rather than any specific design
> factor.
> 
> Whether or not you get away with continuing to use freed memory
> depends upon whether that memory gets re-used. In turn, that depends
> upon which other allocations occur.
> 


-- 
Benjamin Ducke
Senior Applications Support and Development Officer

Oxford Archaeological Unit Limited
Janus House
Osney Mead
OX2 0ES
Oxford, U.K.

Tel: +44 (0)1865 263 800 (switchboard)
Tel: +44 (0)1865 980 758 (direct)
Fax :+44 (0)1865 793 496
benjamin.ducke at oxfordarch.co.uk




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