More fun with valgrind [OLD #21]

[MichaelChirico]

Valgrind detected:

> gh_encode(2.345, 6.789)
==44279== Use of uninitialised value of size 8
==44279==    at 0x48AC549: interleaved_to_geohashstr(unsigned short*, unsigned long, char*, unsigned long) [clone .part.0] (packages/tests-vg/geohashTools/src/geohash.cpp:209)
==44279==    by 0x48AD3FC: interleaved_to_geohashstr (packages/tests-vg/geohashTools/src/geohash.cpp:160)
==44279==    by 0x48AD3FC: geohash_encode_impl (packages/tests-vg/geohashTools/src/geohash.cpp:230)
==44279==    by 0x48AD3FC: gh_encode_(Rcpp::Vector<14, Rcpp::PreserveStorage>, Rcpp::Vector<14, Rcpp::PreserveStorage>, int) (packages/tests-vg/geohashTools/src/geohash.cpp:327)
==44279==    by 0x48A6810: _geohashTools_gh_encode_ (packages/tests-vg/geohashTools/src/RcppExports.cpp:17)
==44279==    by 0x4D18BF: bcEval (svn/R-devel/src/main/eval.c:7293)
==44279==    by 0x4E4F4F: Rf_eval (svn/R-devel/src/main/eval.c:620)
==44279==    by 0x4E6A9E: R_execClosure (svn/R-devel/src/main/eval.c:1780)
==44279==    by 0x4E77E4: Rf_applyClosure (svn/R-devel/src/main/eval.c:1706)
==44279==    by 0x4D6454: bcEval (svn/R-devel/src/main/eval.c:6743)
==44279==    by 0x4E4F4F: Rf_eval (svn/R-devel/src/main/eval.c:620)
==44279==    by 0x4E6A9E: R_execClosure (svn/R-devel/src/main/eval.c:1780)
==44279==    by 0x4E77E4: Rf_applyClosure (svn/R-devel/src/main/eval.c:1706)
==44279==    by 0x4E5044: Rf_eval (svn/R-devel/src/main/eval.c:743)
==44279==  Uninitialised value was created by a stack allocation
==44279==    at 0x48A4080: ??? (in /data/blackswan/ripley/R/packages/tests-vg/geohashTools.Rcheck/geohashTools/libs/geohashTools.so)
==44279== 
[1] "s0kv66"

It appears to be valid -- this loop may access j beyond which dst was initialized:

	for(unsigned int j=0; j<dst_length; j++){
	  Rprintf("Accessing dst[%d]\n", j);
    // 0x1f = 00011111 blanks the leftmost 3 bits to ensure value in [0, 31]
		dst[j] = map[dst[j]&0x1F];
	}

Closed in 73ea7aa