Convert a few int to unsigned int (#402)

src/modbus.c

@@ -353,7 +353,7 @@ int _modbus_receive_msg(modbus_t *ctx, uint8_t *msg, msg_type_t msg_type)
     fd_set rset;
     struct timeval tv;
     struct timeval *p_tv;
-    int length_to_read;
+    unsigned int length_to_read;
     int msg_length = 0;
     _step_t step;
 #ifdef _WIN32
@@ -490,7 +490,7 @@ int _modbus_receive_msg(modbus_t *ctx, uint8_t *msg, msg_type_t msg_type)
                 } /* else switches straight to the next step */
             case _STEP_META:
                 length_to_read = compute_data_length_after_meta(ctx, msg, msg_type);
-                if ((msg_length + length_to_read) > (int) ctx->backend->max_adu_length) {
+                if ((msg_length + length_to_read) > ctx->backend->max_adu_length) {
                     errno = EMBBADDATA;
                     _error_print(ctx, "too many data");
                     return -1;
@@ -554,7 +554,7 @@ static int check_confirmation(modbus_t *ctx, uint8_t *req, uint8_t *rsp, int rsp
 {
     int rc;
     int rsp_length_computed;
-    const int offset = ctx->backend->header_length;
+    const unsigned int offset = ctx->backend->header_length;
     const int function = rsp[offset];
 
     if (ctx->backend->pre_check_confirmation) {
@@ -572,7 +572,7 @@ static int check_confirmation(modbus_t *ctx, uint8_t *req, uint8_t *rsp, int rsp
 
     /* Exception code */
     if (function >= 0x80) {
-        if (rsp_length == (offset + 2 + (int) ctx->backend->checksum_length) &&
+        if (rsp_length == (int) (offset + 2 + ctx->backend->checksum_length) &&
             req[offset] == (rsp[offset] - 0x80)) {
             /* Valid exception code received */
 
@@ -779,7 +779,7 @@ int modbus_reply(modbus_t *ctx,
                  int req_length,
                  modbus_mapping_t *mb_mapping)
 {
-    int offset;
+    unsigned int offset;
     int slave;
     int function;
     uint16_t address;
@@ -1139,7 +1139,7 @@ int modbus_reply(modbus_t *ctx,
 
 int modbus_reply_exception(modbus_t *ctx, const uint8_t *req, unsigned int exception_code)
 {
-    int offset;
+    unsigned int offset;
     int slave;
     int function;
     uint8_t rsp[MAX_MESSAGE_LENGTH];
@@ -1184,10 +1184,10 @@ static int read_io_status(modbus_t *ctx, int function, int addr, int nb, uint8_t
 
     rc = send_msg(ctx, req, req_length);
     if (rc > 0) {
-        int i, temp, bit;
+        int temp, bit;
         int pos = 0;
-        int offset;
-        int offset_end;
+        unsigned int offset;
+        unsigned int offset_end;
 
         rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
         if (rc == -1)
@@ -1199,7 +1199,7 @@ static int read_io_status(modbus_t *ctx, int function, int addr, int nb, uint8_t
 
         offset = ctx->backend->header_length + 2;
         offset_end = offset + rc;
-        for (i = offset; i < offset_end; i++) {
+        for (unsigned int i = offset; i < offset_end; i++) {
             /* Shift reg hi_byte to temp */
             temp = rsp[i];
 
@@ -1295,7 +1295,7 @@ static int read_registers(modbus_t *ctx, int function, int addr, int nb, uint16_
 
     rc = send_msg(ctx, req, req_length);
     if (rc > 0) {
-        int offset;
+        unsigned int offset;
         int i;
 
         rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
@@ -1630,7 +1630,7 @@ int modbus_write_and_read_registers(modbus_t *ctx,
 
     rc = send_msg(ctx, req, req_length);
     if (rc > 0) {
-        int offset;
+        unsigned int offset;
 
         rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
         if (rc == -1)
@@ -1672,7 +1672,7 @@ int modbus_report_slave_id(modbus_t *ctx, int max_dest, uint8_t *dest)
     rc = send_msg(ctx, req, req_length);
     if (rc > 0) {
         int i;
-        int offset;
+        unsigned int offset;
         uint8_t rsp[MAX_MESSAGE_LENGTH];
 
         rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);