mraa: Fix compiler warnings unused vars and useless statements

Should have 0 functionality effect, just cleans up a few things. Fixes #577

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

docs/building.md

@@ -102,6 +102,10 @@ Override build architecture (this is useful because on x86 ARM code is not
 compiled so use this flag to force the target arch)
  `-DBUILDARCH=arm`
 
+You can also enable -Wall for gcc before running cmake by exporting your wanted
+CC flags to the CC env var
+  `export CC="gcc -Wall"`
+
 ## Dependencies continued
 
 You'll need at least SWIG version 3.0.2 and we recommend 3.0.5 to build the

examples/cycle-pwm3.c

@@ -49,6 +49,7 @@ main()
             value = 0.0f;
         }
         float output = mraa_pwm_read(pwm);
+        printf("PWM value is %f\n", output);
     }
     //! [Interesting]
     return 0;

examples/iio_driver.c

@@ -55,7 +55,7 @@ interrupt(char* data)
     mraa_iio_channel* channels = mraa_iio_get_channels(iio_device0);
     int i = 0;
 
-    for (i; i < mraa_iio_get_channel_count(iio_device0); i++) {
+    for (; i < mraa_iio_get_channel_count(iio_device0); i++) {
         if (channels[i].enabled) {
             printf("channel %d - bytes %d\n", channels[i].index, channels[i].bytes);
             switch (channels[i].bytes) {

examples/mraa-i2c.c

@@ -144,7 +144,6 @@ i2c_set_exit:
 void
 i2c_detect_devices(int bus)
 {
-    mraa_result_t status = MRAA_SUCCESS;
     mraa_i2c_context i2c = mraa_i2c_init(bus);
     if (i2c == NULL) {
         return;

examples/spi_mcp4261.c

@@ -33,7 +33,6 @@ main(int argc, char** argv)
     //! [Interesting]
     mraa_spi_context spi;
     spi = mraa_spi_init(0);
-    unsigned int response = 0;
     printf("Hello, SPI initialised\n");
     uint8_t data[] = { 0x00, 100 };
     uint8_t* recv;

src/iio/iio.c

@@ -309,7 +309,7 @@ mraa_iio_wait_event(int fd, char* data, int* read_size)
 
     // Wait for it forever or until pthread_cancel
     // poll is a cancelable point like sleep()
-    int x = poll(&pfd, 1, -1);
+    poll(&pfd, 1, -1);
 
     memset(data, 0, 100);
     *read_size = read(fd, data, 100);
@@ -376,10 +376,7 @@ mraa_iio_get_event_data(mraa_iio_context dev)
     char buf[MAX_SIZE];
     char readbuf[32];
     int fd;
-    int ret = 0;
-    int padint = 0;
-    int curr_bytes = 0;
-    char shortbuf, signchar;
+
     memset(buf, 0, MAX_SIZE);
     memset(readbuf, 0, 32);
     snprintf(buf, MAX_SIZE, IIO_SYSFS_DEVICE "%d/" IIO_EVENTS, dev->num);
@@ -441,7 +438,7 @@ mraa_iio_event_poll_nonblock(int fd, struct iio_event_data* data)
 
     // Wait for it forever or until pthread_cancel
     // poll is a cancelable point like sleep()
-    int x = poll(&pfd, 1, -1);
+    poll(&pfd, 1, -1);
 
     read(fd, data, sizeof(struct iio_event_data));
 
@@ -573,9 +570,7 @@ mraa_result_t
 mraa_iio_create_trigger(mraa_iio_context dev, const char* trigger)
 {
     struct stat configfs_status;
-    struct stat trigger_status;
     char buf[MAX_SIZE];
-    int ret;
 
     if (stat(IIO_CONFIGFS_TRIGGER, &configfs_status) == 0) {
         memset(buf, 0, MAX_SIZE);

src/json/jsonplatform.c

@@ -80,7 +80,6 @@ mraa_init_json_platform_platform(json_object* jobj_platform, mraa_board_t* board
 {
     json_object* jobj_temp = NULL;
     const char* temp_string = NULL;
-    int temp_count = 0;
     int length = 0;
     mraa_result_t ret = MRAA_SUCCESS;
 
@@ -600,8 +599,8 @@ mraa_init_json_platform(const char* platform_json)
     mraa_result_t ret = MRAA_SUCCESS;
     char* buffer = NULL;
     struct stat st;
-    int file_lock = 0, array_length = 0, i = 0;
-    json_object *jobj_platform = NULL, *jobj_temp = NULL;
+    int file_lock = 0, i = 0;
+    json_object *jobj_platform = NULL;
     mraa_board_t* board = NULL;
 
     // Try to lock the file for use

src/mraa.c

@@ -69,7 +69,6 @@ mraa_iio_info_t* plat_iio = NULL;
 mraa_lang_func_t* lang_func = NULL;
 
 char* platform_name = NULL;
-static char* platform_long_name = NULL;
 
 static int num_i2c_devices = 0;
 static int num_iio_devices = 0;
@@ -953,7 +952,7 @@ mraa_find_i2c_bus(const char* devname, int startfrom)
     // i2c devices are numbered numerically so 0 must exist otherwise there is
     // no i2c-dev loaded
     if (mraa_file_exist("/sys/class/i2c-dev/i2c-0")) {
-        for (i; i < num_i2c_devices; i++) {
+        for (;i < num_i2c_devices; i++) {
             off_t size, err;
             snprintf(path, 64, "/sys/class/i2c-dev/i2c-%u/name", i);
             fd = open(path, O_RDONLY);

src/uart_ow/uart_ow.c

@@ -320,7 +320,7 @@ mraa_uart_ow_bit(mraa_uart_ow_context dev, uint8_t bit)
     /* return the bit present on the bus (0xff is a '1', anything else
      * (typically 0xfc or 0x00) is a 0
      */
-    if (_ow_read_byte(dev, &ch) == -1 || ret == -1) {
+    if (_ow_read_byte(dev, &ch) != MRAA_SUCCESS || ret == -1) {
          return -1;
     }
     return (ch == 0xff);

src/x86/intel_minnow_byt_compatible.c

@@ -89,7 +89,7 @@ mraa_intel_minnowboard_byt_compatible(mraa_boolean_t turbot)
     mraa_board_t* b = (mraa_board_t*) calloc(1, sizeof(mraa_board_t));
 
     struct utsname running_uname;
-    int uname_major, uname_minor, max_pins[28];
+    int uname_major, uname_minor;
 
     if (b == NULL) {
         return NULL;

src/x86/up.c

@@ -86,7 +86,7 @@ mraa_up_board()
     mraa_board_t* b = (mraa_board_t*) calloc(1, sizeof(mraa_board_t));
 
     struct utsname running_uname;
-    int uname_major, uname_minor, max_pins[27];
+    int uname_major, uname_minor;
 
     if (b == NULL) {
         return NULL;