C: Fixes for sign compares in C libraries

Added explicit error for sign compares to CMake.  Updated a handful of C
source which compared unsigned vs signed.

Signed-off-by: Noel Eck <noel.eck@intel.com>

CMakeLists.txt

@@ -104,6 +104,7 @@ endif (WERROR)
 upm_add_compile_flags(C ${C_CXX_WARNING_FLAGS}
   -Winit-self
   -Wimplicit
+  -Wsign-compare
   -Wmissing-parameter-type)
 
 # Set CXX compiler warning flags at top-level scope and emit a warning about
@@ -111,6 +112,7 @@ upm_add_compile_flags(C ${C_CXX_WARNING_FLAGS}
 upm_add_compile_flags(CXX ${C_CXX_WARNING_FLAGS}
   -Wnon-virtual-dtor
   -Woverloaded-virtual
+  -Wsign-compare
   -Wreorder)
 
 # Allow exception error handling for Android C++

examples/c/ds18b20.c

@@ -62,8 +62,7 @@ int main(int argc, char **argv)
         // update our values for all sensors
         ds18b20_update(sensor, -1);
 
-        int i;
-        for (i=0; i<ds18b20_devices_found(sensor); i++)
+        for (unsigned int i=0; i<ds18b20_devices_found(sensor); i++)
         {
             printf("Device %02d: Temperature: %f C\n",
                     i, ds18b20_get_temperature(sensor, i));

src/bno055/bno055.c

@@ -318,7 +318,7 @@ upm_result_t bno055_write_regs(const bno055_context dev, uint8_t reg,
     uint8_t buf[len + 1];
 
     buf[0] = reg;
-    for (int i=0; i<len; i++)
+    for (size_t i=0; i<len; i++)
         buf[i+1] = buffer[i];
 
     if (mraa_i2c_write(dev->i2c, buf, len + 1))

src/ds18b20/ds18b20.c

@@ -143,8 +143,7 @@ ds18b20_context ds18b20_init(unsigned int uart)
     }
 
     // iterate through the found devices and query their resolutions
-    int i;
-    for (i=0; i<dev->numDevices; i++)
+    for (unsigned int i=0; i<dev->numDevices; i++)
     {
         // read only the first 5 bytes of the scratchpad
         static const int numScratch = 5;
@@ -191,7 +190,7 @@ void ds18b20_update(const ds18b20_context dev, int index)
 {
     assert(dev != NULL);
 
-    if (index >= dev->numDevices)
+    if (index >= (int)dev->numDevices)
     {
         printf("%s: device index %d out of range\n", __FUNCTION__, index);
         return;
@@ -206,9 +205,7 @@ void ds18b20_update(const ds18b20_context dev, int index)
         // convert command to all of them, then wait.  This will be
         // faster, timey-wimey wise, then converting, sleeping, and
         // reading each individual sensor.
-
-        int i;
-        for (i=0; i<dev->numDevices; i++)
+        for (unsigned int i=0; i<dev->numDevices; i++)
             mraa_uart_ow_command(dev->ow, DS18B20_CMD_CONVERT, dev->devices[i].id);
     }
     else
@@ -219,8 +216,7 @@ void ds18b20_update(const ds18b20_context dev, int index)
 
     if (doAll)
     {
-        int i;
-        for (i=0; i<dev->numDevices; i++)
+        for (unsigned int i=0; i<dev->numDevices; i++)
             dev->devices[i].temperature = readSingleTemp(dev, i);
     }
     else

src/ds18b20/ds18b20.h

@@ -53,7 +53,7 @@ extern "C" {
         mraa_uart_ow_context ow;
 
         // number of devices found
-        int numDevices;
+        unsigned int numDevices;
 
         // list of allocated ds18b20_info_t instances
         ds18b20_info_t *devices;

src/ecezo/ecezo.c

@@ -395,7 +395,7 @@ int ecezo_read(const ecezo_context dev, char *buffer, size_t len)
     else
     {
         // UART
-        int bytesRead = 0;
+        size_t bytesRead = 0;
 
         while(bytesRead < len)
         {
@@ -437,7 +437,7 @@ upm_result_t ecezo_write(const ecezo_context dev, char *buffer, size_t len)
 
     if (dev->uart)
     {
-        if (mraa_uart_write(dev->uart, buffer, len) != len)
+        if (mraa_uart_write(dev->uart, buffer, len) != (int)len)
         {
             printf("%s: mraa_uart_write() failed.\n", __FUNCTION__);
             return UPM_ERROR_OPERATION_FAILED;

src/enc03r/enc03r.c

@@ -105,7 +105,7 @@ upm_result_t enc03r_calibrate(const enc03r_context dev,
 
     float total = 0.0;
 
-    for (int i=0; i<samples; i++)
+    for (unsigned int i=0; i<samples; i++)
     {
         int val = mraa_aio_read(dev->aio);
         if (val < 0)

src/m24lr64e/m24lr64e.c

@@ -303,7 +303,7 @@ upm_result_t m24lr64e_eeprom_write_bytes(m24lr64e_context dev,
 
 upm_result_t m24lr64e_eeprom_read_byte(m24lr64e_context dev, uint32_t address,
                                        uint8_t* data){
-    uint32_t pkt_len = 2;
+    int pkt_len = 2;
     uint8_t buf[pkt_len];
 
     buf[0] = ((address >> 8) & 0xff);

src/mcp2515/mcp2515.c

@@ -315,7 +315,7 @@ upm_result_t mcp2515_bus_read(const mcp2515_context dev, uint8_t cmd,
 
     if (args && arglen)
     {
-        for (int i=0; i<arglen; i++)
+        for (unsigned int i=0; i<arglen; i++)
             sbuf[index++] = args[i];
     }
 

src/ppd42ns/ppd42ns.c

@@ -93,7 +93,7 @@ ppd42ns_dust_data ppd42ns_get_data(const ppd42ns_context dev)
     ppd42ns_dust_data data;
 
     // in ms, 30 seconds
-    const int pulse_check_time = 30000;
+    const unsigned int pulse_check_time = 30000;
     // loop timer
     upm_clock_t max_loop_time;
 

src/rn2903/rn2903.c

@@ -347,14 +347,14 @@ RN2903_RESPONSE_T rn2903_waitfor_response(const rn2903_context dev,
 
             dev->resp_len++;
         }
-    } while ( (elapsed = upm_elapsed_ms(&clock)) < wait_ms);
+    } while ( (int)(elapsed = upm_elapsed_ms(&clock)) < wait_ms);
 
     if (dev->debug)
         printf("\tRESP (%d): '%s'\n", (int)dev->resp_len,
                (dev->resp_len) ? dev->resp_data : "");
 
     // check for and return obvious errors
-    if (elapsed >= wait_ms)
+    if ((int)elapsed >= wait_ms)
         return RN2903_RESPONSE_TIMEOUT;
     else if (rn2903_find(dev, RN2903_PHRASE_INV_PARAM))
         return RN2903_RESPONSE_INVALID_PARAM;

src/servo/es08a.c

@@ -86,7 +86,7 @@ upm_result_t es08a_set_angle(es08a_context dev, int32_t angle){
 
 upm_result_t es08a_calc_pulse_travelling(const es08a_context dev,
                                          int32_t* ret_val, int32_t value){
-    if (value > dev->max_pulse_width) {
+    if (value > (int)dev->max_pulse_width) {
         return dev->max_pulse_width;
     }
 

src/servo/es9257.c

@@ -87,7 +87,7 @@ upm_result_t es9257_set_angle(es9257_context dev, int32_t angle){
 
 upm_result_t es9257_calc_pulse_travelling(const es9257_context dev,
                                          int32_t* ret_val, int32_t value){
-    if (value > dev->max_pulse_width) {
+    if (value > (int)dev->max_pulse_width) {
         return dev->max_pulse_width;
     }
 

src/uartat/uartat.c

@@ -268,7 +268,7 @@ int uartat_command_with_response(const uartat_context dev,
         upm_clock_t clock;
         upm_clock_init(&clock);
 
-        int idx = 0;
+        size_t idx = 0;
 
         do
         {
@@ -323,7 +323,7 @@ bool uartat_command_waitfor(const uartat_context dev, const char *cmd,
     upm_clock_t clock;
     upm_clock_init(&clock);
 
-    int idx = 0;
+    size_t idx = 0;
 
     do
     {