decode()ing non-ASCII characters is UBSAN error

[MichaelChirico]

From wch1/r-debug::RDsan

gh_decode('ß')
=================================================================
==116==ERROR: AddressSanitizer: global-buffer-overflow on address 0x7fd1de376b5c at pc 0x7fd1de375172 bp 0x7fff825736e0 sp 0x7fff825736d0
READ of size 4 at 0x7fd1de376b5c thread T0
    #0 0x7fd1de375171 in gh_decode /geohashTools/src/geohash.c:159
    #1 0x7fd1e98209ca in R_doDotCall /tmp/r-source/src/main/dotcode.c:576
    #2 0x7fd1e99114e6 in bcEval /tmp/r-source/src/main/eval.c:7293
    #3 0x7fd1e98bcfef in Rf_eval /tmp/r-source/src/main/eval.c:620
    #4 0x7fd1e98c2e8b in R_execClosure /tmp/r-source/src/main/eval.c:1780
    #5 0x7fd1e98c25d9 in Rf_applyClosure /tmp/r-source/src/main/eval.c:1706
    #6 0x7fd1e98be2b8 in Rf_eval /tmp/r-source/src/main/eval.c:743
    #7 0x7fd1e9965017 in Rf_ReplIteration /tmp/r-source/src/main/main.c:260
    #8 0x7fd1e9965412 in R_ReplConsole /tmp/r-source/src/main/main.c:310
    #9 0x7fd1e9967882 in run_Rmainloop /tmp/r-source/src/main/main.c:1108
    #10 0x7fd1e9967898 in Rf_mainloop /tmp/r-source/src/main/main.c:1115
    #11 0x55bd82594ac0 in main /tmp/r-source/src/main/Rmain.c:29
    #12 0x7fd1e84e6b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
    #13 0x55bd82594999 in _start (/usr/local/RDsan/lib/R/bin/exec/R+0x999)

0x7fd1de376b5c is located 56 bytes to the right of global variable 'centeroffx' defined in 'geohash.h:51:18' (0x7fd1de376b00) of size 36
0x7fd1de376b5c is located 4 bytes to the left of global variable 'centeroffy' defined in 'geohash.h:52:18' (0x7fd1de376b60) of size 36
SUMMARY: AddressSanitizer: global-buffer-overflow /geohashTools/src/geohash.c:159 in gh_decode
Shadow bytes around the buggy address:
  0x0ffabbc66d10: 00 00 00 00 00 00 00 00 f9 f9 f9 f9 00 00 00 00
  0x0ffabbc66d20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffabbc66d30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffabbc66d40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffabbc66d50: 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9
=>0x0ffabbc66d60: 00 00 00 00 04 f9 f9 f9 f9 f9 f9[f9]00 00 00 00
  0x0ffabbc66d70: 04 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 00 00 00 00
  0x0ffabbc66d80: 00 00 00 02 f9 f9 f9 f9 00 00 00 00 00 00 00 06
  0x0ffabbc66d90: f9 f9 f9 f9 00 00 00 00 00 00 03 f9 f9 f9 f9 f9
  0x0ffabbc66da0: 00 00 00 00 00 01 f9 f9 f9 f9 f9 f9 00 02 f9 f9
  0x0ffabbc66db0: f9 f9 f9 f9 00 07 f9 f9 f9 f9 f9 f9 00 00 f9 f9
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==116==ABORTING

It's pretty clear -- we're trying to access the map array way outside its allocated boundaries:

charToRaw('ß')
[1] c3 9f