helper/binarybuffer: fix clang static analyzer warnings

Writing bits to an uninitialized buffer generated false warnings.
Zero buffers before setting them by buf_set_u32|64()
(do it only if bit-by-bit copy loop is used,
zeroed buffer is not necessary if a fast path write is used)

Change-Id: I2f7f8ddb45b0cbd08d3e249534fc51f4b5cc6694
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/5383
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>

src/jtag/core.c

@@ -1233,7 +1233,7 @@ static int jtag_examine_chain(void)
 	/* Add room for end-of-chain marker. */
 	max_taps++;
 
-	uint8_t *idcode_buffer = malloc(max_taps * 4);
+	uint8_t *idcode_buffer = calloc(4, max_taps);
 	if (idcode_buffer == NULL)
 		return ERROR_JTAG_INIT_FAILED;
 

src/jtag/tcl.c

@@ -1131,7 +1131,7 @@ COMMAND_HANDLER(handle_irscan_command)
 		}
 		int field_size = tap->ir_length;
 		fields[i].num_bits = field_size;
-		uint8_t *v = malloc(DIV_ROUND_UP(field_size, 8));
+		uint8_t *v = calloc(1, DIV_ROUND_UP(field_size, 8));
 
 		uint64_t value;
 		retval = parse_u64(CMD_ARGV[i * 2 + 1], &value);