Question

When I’m trying to compile this code with gcc version 4.6.3 on linux with -Wall flag I’m getting these two warnings:

1. It points to cmd[1]=cmd2send;

   warning: assignment makes pointer from integer without a cast [enabled by default]

2. It points to the variable static unsigned char *cmd[65]

   warning: variable ‘cmd’ set but not used [-Wunused-but-set-variable].

What makes these warnings? and how to avoid them?

  int CommandHandler(unsigned char cmd2send)
    {
        static unsigned char *cmd[65];

        // *make sure device is open*
        if(handle==NULL) // handle defined in transceiver.h
        {
            puts("CommandHandler::Cant handle command");
            // try to open device again
            if(OpenMyDev()!=0)
            return -1;
            // if no return then retry is fine
            puts("retry SUCCEEDED!, device is open");
        }

        // *send command to firmware*
        cmd[0]=0x0;
        cmd[1]=cmd2send;
        .......
        return 0;

    }

Here, also I’m getting warning #2 for variable voltage:

float Get_Temperature(void)
{
    //unsigned char RecvByte=0;
    //int byte[4];

    int i;

    float voltage=0;
    float resistance=0;
    float temperature=0;
    float SamplesAVG=0;

    unsigned int Samples=0;

    unsigned char* rvc;
    unsigned char mydata[65];


    for(i=0;i<=10;i++)
    {
        //Transimit Start Of Frame
        mydata[0]=0;
        mydata[1]=GET_TEMPERATURE;

        if(Write2MyDev(mydata)<0)  {return -1;}

        rvc=ReadMyDev(0);

        SamplesAVG+=(rvc[0]<<24)+(rvc[1]<<16)+(rvc[2]<<8)+rvc[3];
        usleep(100*1000);
    }

    Samples=SamplesAVG/10;
    printf("TO PRINT VAL:%d\n",Samples);
    puts("------------");

    voltage = (Samples * 5.0)/1023.0; // 0..1203= 1024 values
    resistance = 10000.0/ (1023.0/Samples);
    ...
    return retval;
}

Answer 1

cmd2send is an unsigned char and you are setting the value at cmd[1] which is a char * to it. A char * is a pointer and an unsigned char is treated like an integer so you are making a pointer cmd[1] from an integer without a cast.

Chances are you wanted an array of characters char cmd[65] not an array of char *

Also since you created and assigned values to cmd but you never use it you get a warning for that as well.