Fixed small distance replies on GEODIST and GEO commands WITHDIST (#11631)

Fixes a regression introduced by #11552 in 7.0.6.
it causes replies in the GEO commands to contain garbage when the
result is a very small distance (less than 1)
Includes test to confirm indeed with junk in buffer now we properly reply

1 files changed, 17 insertions, 7 deletions

diff --git a/src/util.c b/src/util.c
index d094b3b55..74508a70f 100644
--- a/src/util.c
+++ b/src/util.c
@@ -656,9 +656,7 @@ int fixedpoint_d2string(char *dst, size_t dstlen, double dvalue, int fractional_
     if (dvalue == 0) {
         dst[0] = '0';
         dst[1] = '.';
-        for (int i = 0; i < fractional_digits; i++) {
-            dst[2 + i] = '0';
-        }
+        memset(dst + 2, '0', fractional_digits);
         dst[fractional_digits+2] = '\0';
         return fractional_digits + 2;
     }
@@ -707,10 +705,8 @@ int fixedpoint_d2string(char *dst, size_t dstlen, double dvalue, int fractional_
     }
     dst[integer_digits] = '.';
     int size = integer_digits + 1 + fractional_digits;
-    /* fill with 0 if required until fractional_digits */
-    for (int i = integer_digits + 1; i < fractional_digits; i++) {
-        dst[i] = '0';
-    }
+    /* fill with 0 from fractional digits until size */
+    memset(dst + integer_digits + 1, '0', fractional_digits);
     int next = size - 1;
     while (value >= 100) {
         int const i = (value % 100) * 2;
@@ -1282,6 +1278,20 @@ static void test_fixedpoint_d2string(void) {
     sz = fixedpoint_d2string(buf, sizeof buf, v, 1);
     assert(sz == 3);
     assert(!strcmp(buf, "0.0"));
+    /* set junk in buffer */
+    memset(buf,'A',32);
+    v = 0.0001;
+    sz = fixedpoint_d2string(buf, sizeof buf, v, 4);
+    assert(sz == 6);
+    assert(buf[sz] == '\0');
+    assert(!strcmp(buf, "0.0001"));
+    /* set junk in buffer */
+    memset(buf,'A',32);
+    v = 6.0642951598391699e-05;
+    sz = fixedpoint_d2string(buf, sizeof buf, v, 4);
+    assert(sz == 6);
+    assert(buf[sz] == '\0');
+    assert(!strcmp(buf, "0.0001"));
     v = 0.01;
     sz = fixedpoint_d2string(buf, sizeof buf, v, 4);
     assert(sz == 6);