PolarVolume_getScanClosestToElevation_vol2bird() leads to segfault when using cluttermap

[adokter]

New function PolarVolume_getScanClosestToElevation_vol2bird() leads to a segfault when selecting cluttermap elevation scans. Reverting to PolarVolume_getScanClosestToElevation() solves the issue.

[adokter]

This suggests that potentially something is wrong with PolarVolume_getScanClosestToElevation_vol2bird(), which is used in elevation scan selection in Mistnet, see #148.

[adokter]

Reverting back to PolarVolume_getScanClosestToElevation() in 4adfaa7 fixes the issue for now.

Verified that PolarVolume_getScanClosestToElevation_vol2bird() selects the correct scan at the end of its function body, however when accessing returned object clutScan here the program crashes:

vol2bird/lib/libvol2bird.c

Lines 1989 to 1992 in 4adfaa7

	//FIXME: here PolarVolume_getScanClosestToElevation_vol2bird leads to a segmentation fault. It finds the correct scan, but
	//any operation here on the pointer leads to segfault...
	//clutScan = PolarVolume_getScanClosestToElevation_vol2bird(clutVol,elev);
	clutScan = PolarVolume_getScanClosestToElevation(clutVol,elev,0);

Need more solid fix, leaving issue open

[adokter]

What causes the segfault, is that the pointer returned in the function body of PolarVolume_getScanClosestToElevation_vol2bird() - and which I verified points to a proper Rave scan object - is not equal to the pointer received by the function call, as it should be.

Unfortunately valgrind doesn't give good clues; the process runs normally and the pointer IS correctly returned in valgrind runs. So potentially this is a memory issue occurring somewhere different entirely. Valgrind also finds no unrecoverable memory leaks:

valgrind --leak-check=full vol2bird KCBX20180703_185917_V06
==25583== Memcheck, a memory error detector
==25583== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==25583== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==25583== Command: vol2bird KCBX20180703_185917_V06
==25583== 
Loaded user configuration file 'options.conf' ...
Reading RSL polar volume with nominal time 20180703-185917, source: RAD:KCBX,PLC:BOISE,state:ID,radar_name:KCBX

==25583== 
==25583== HEAP SUMMARY:
==25583==     in use at exit: 250,148,074 bytes in 12,298 blocks
==25583==   total heap usage: 315,963 allocs, 303,665 frees, 448,826,117 bytes allocated
==25583== 
==25583== LEAK SUMMARY:
==25583==    definitely lost: 0 bytes in 0 blocks
==25583==    indirectly lost: 0 bytes in 0 blocks
==25583==      possibly lost: 0 bytes in 0 blocks
==25583==    still reachable: 250,148,074 bytes in 12,298 blocks
==25583==                       of which reachable via heuristic:
==25583==                         stdstring          : 319,918 bytes in 4,373 blocks
==25583==         suppressed: 0 bytes in 0 blocks
==25583== Reachable blocks (those to which a pointer was found) are not shown.
==25583== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==25583== 
==25583== For counts of detected and suppressed errors, rerun with: -v
==25583== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)