Question

/* DECLARED FUNCTIONS */
char *DetectDevice(void);

int main(int argc, char *argv[])
{
    char *PathToDevice;
    PathToDevice = DetectDevice();

...

    if(close(fd) == -1)
    {
        printf("Error Closing Port");
    }else
    {
        printf("whihi!");
        free(PathToDevice);
    }

    return 0;
}

char *DetectDevice(void)
{   
    char *Usbs = malloc(1024);
    Usbs = "/dev/ttyUSB1";
    return Usbs;
}

Error Message: * glibc detected * ./test: free(): invalid pointer: 0xbec1b504

by the way… this program is compiled on a raspberry pi!

Answer 1

Usbs = "/dev/ttyUSB1"; changes Usbs to point to a string literal. This may exist in read-only memory and cannot be freed. Use

char *DetectDevice(void)
{   
    char *Usbs = malloc(1024);
    strcpy(Usbs, "/dev/ttyUSB1");
    return Usbs;
}

to copy the string, or

char *DetectDevice(void)
{   
    return strdup("/dev/ttyUSB1");
}

to allocate the string with just the right amount of memory instead.

Alternatively, you could also recognise that DetectDevice returns a read-only string

const char *DetectDevice(void)
{   
    return "/dev/ttyUSB1";
}

and remove the free from calling code instead.