crash in NSData subdataWithRange

after updating the xcode to 8.2. I rebuild one of my old project, found the APP will crash when [NSData subdataWithRange], if call it many times (more than 50), it will crash. But the code is normal before, i did nothing change for it.

the code as below:

while (alreadySndLen < fileSize)

{

sndDataLen = (unsigned int)MIN(SEND_SLICE_SIZE, (fileSize - alreadySndLen));

cmdHead.msgOffset = (unsigned int)alreadySndLen;

cmdHead.msgLength = sizeof(FILE_HEAD) + (unsigned int)sndDataLen;

sndRange.location = alreadySndLen;

sndRange.length = sndDataLen;

NSMutableData *cmdData = [[NSMutableData alloc] initWithBytes:&cmdHead length:sizeof(CMD_HEAD)];

[cmdData appendBytes:&fileHead length:sizeof(FILE_HEAD)];

NSLog(@"new file len:%lu", (unsigned long)fileData.length);

NSData *subData = [fileData subdataWithRange:sndRange];

if (nil == subData)

{

NSLog(@"sub data %@ is nil", NSStringFromRange(sndRange));

}

else

{

[cmdData appendData:subData];

}

/

alreadySndLen += sndDataLen;

float progress = (float)alreadySndLen/(float)fileSize;

if (![[MMCMDMgr sharedCMDMgr] uploadFileSliceData:cmdData ofNode:memoID ofSlice:sliceID ofUser:usrID ofType:fileType ofProgress:progress])

{

return FALSE;

}

}