jtag: fix build with configure --enable-verbose

With flag --enable-verbose, configure enables compiling some
conditional code that with new gcc triggers an error:
	error: '%04x' directive output may be truncated writing
	between 4 and 8 bytes into a region of size 5
	[-Werror=format-truncation=]

Extend the buffer to contain the full 8 bytes of %04x on a 'int'
and change the limit in snprintf.
Skip the intermediate buffer 's[4]'.
Align the code to the coding style.

Change-Id: Ifc8a6e4686555578a7355a1f6049471fd5e31913
Signed-off-by: Antonio Borneo <[email protected]>
Reported-by: Karl Hammar <[email protected]>
Reported-by: Tommy Murphy <[email protected]>
Fixes: https://sourceforge.net/p/openocd/tickets/376/
Reviewed-on: https://review.openocd.org/c/openocd/+/7403
Tested-by: jenkins
Reviewed-by: Tomas Vanek <[email protected]>

Author: borneoa

src/jtag/drivers/arm-jtag-ew.c

@@ -776,17 +776,12 @@ static int armjtagew_usb_read(struct armjtagew *armjtagew, int exp_in_length)
 
 static void armjtagew_debug_buffer(uint8_t *buffer, int length)
 {
-	char line[81];
-	char s[4];
-	int i;
-	int j;
+	char line[8 + 3 * BYTES_PER_LINE + 1];
 
-	for (i = 0; i < length; i += BYTES_PER_LINE) {
-		snprintf(line, 5, "%04x", i);
-		for (j = i; j < i + BYTES_PER_LINE && j < length; j++) {
-			snprintf(s, 4, " %02x", buffer[j]);
-			strcat(line, s);
-		}
+	for (int i = 0; i < length; i += BYTES_PER_LINE) {
+		int n = snprintf(line, 9, "%04x", i);
+		for (int j = i; j < i + BYTES_PER_LINE && j < length; j++)
+			n += snprintf(line + n, 4, " %02x", buffer[j]);
 		LOG_DEBUG("%s", line);
 
 		/* Prevent GDB timeout (writing to log might take some time) */

src/jtag/drivers/opendous.c

@@ -796,17 +796,12 @@ int opendous_usb_read(struct opendous_jtag *opendous_jtag)
 
 void opendous_debug_buffer(uint8_t *buffer, int length)
 {
-	char line[81];
-	char s[4];
-	int i;
-	int j;
+	char line[8 + 3 * BYTES_PER_LINE + 1];
 
-	for (i = 0; i < length; i += BYTES_PER_LINE) {
-		snprintf(line, 5, "%04x", i);
-		for (j = i; j < i + BYTES_PER_LINE && j < length; j++) {
-			snprintf(s, 4, " %02x", buffer[j]);
-			strcat(line, s);
-		}
+	for (int i = 0; i < length; i += BYTES_PER_LINE) {
+		int n = snprintf(line, 9, "%04x", i);
+		for (int j = i; j < i + BYTES_PER_LINE && j < length; j++)
+			n += snprintf(line + n, 4, " %02x", buffer[j]);
 		LOG_DEBUG("%s", line);
 	}
 }