XCode strcpy ( char *dest, io_name_t src) not copying to dest

Question

This has to be a simple error on my part, hence why I use the term "not working" with hesitation.

Here is my code, the problem is the strcpy from io_name_t variable to char array seems to not work, i.e. the data is not copied.

Define the struct to hold the data for further use:

static struct sUSBDevInfo {
    char devName[200];
    char svcPlane[200];
    char othPlane[200];
    int  isScreen;
} USBDevInfo[99];

Now populate the struct:

int getUSBDevices ()
{
    int i = -1;

    CFMutableDictionaryRef matchingDict;
    io_iterator_t iter;
    kern_return_t kr;
    io_service_t device;
    io_name_t    deviceName;
    io_string_t  pathName;

    matchingDict = IOServiceMatching(kIOUSBDeviceClassName);
    if ( matchingDict == NULL)
    {
        return ( "No match" );
    }
    /* Now we have a dictionary, get an iterator.*/
    kr = IOServiceGetMatchingServices(kIOMasterPortDefault, matchingDict, &iter);
    if (kr != KERN_SUCCESS)
    {
        return (0);
    }

    /* iterate */
    while ((device = IOIteratorNext(iter)))
    {
        /* do something with device, eg. check properties */
                 /***Display the device names ***/

        kr = IORegistryEntryGetName(device, deviceName);
        if (KERN_SUCCESS != kr)
        {
            deviceName[0] = '\0';

        }
        i++;
        printf("\ndeviceName:%s",deviceName);
        strcpy(USBDevInfo[i].devName, deviceName);    /* !!! This and the following strcpy leave the dest variable unchanged !!! */
        IORegistryEntryGetPath(device, kIOServicePlane, pathName);
        strcpy(USBDevInfo[i].svcPlane, pathName);
        IORegistryEntryGetPath(device, kIOUSBPlane, pathName);
        strcpy(USBDevInfo[i].othPlane, pathName);
        USBDevInfo[i].isScreen = isScreen(deviceName);
        IOObjectRelease(device);
    }

    /* Done, release the iterator */
    IOObjectRelease(iter);
    return ( i );
}

When I debug it shows that deviceName has expected values (e.g. deviceName:Root Hub Simulation Simulation) , but the strcpy to USBDevInfo[i].devName leaves the destination unchanged ('\0').

Edit.

Tried experimenting. Copy to another local variable works, but no to the global static struct item:

char cpy[200];      /* local variable */
.
.
strcpy(cpy, deviceName);                   /* Works - copied to cpy */
strcpy(USBDevInfo[i].devName, deviceName); /* Not working */
USBDevInfo[i].devName[0] = deviceName[3];  /* Not working */

Edit 2

See the answer below.

so if it's working for you now with your "Edit 2" changes, is there still a question? — Michael Dautermann, Dec 19 '17 at 23:44

TenG · Accepted Answer · 2017-12-20T19:10:18.923

Edit 2

Amended the header file to contain just a type definition of the struct.

typedef  struct sUSBDevInfo {
    char devName[400];
    char svcPlane[400];
    char othPlane[400];
    int  isScreen;
} tUSBDevInfo;

Moved the struct variable declarations to the C file.

static  tUSBDevInfo USBDevInfo[99];

Now the strcpy works.

So, putting the struct array variable in the header causes the code to not be able to change the values in the array, but putting it in the c file (as a global) works.

XCode strcpy ( char *dest, io_name_t src) not copying to dest

1 Answers1