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问题 I have a struct iof_header in my code, and I determined it would be 24 bytes wide. I perform a sizeof(iof_header) and it returns 32 bytes wide. Question 1 Why is it 32 bytes wide instead of 24? Question 2 Including its members, how is a struct stored in memory? Question 3 I find any time I create one of my structs that bytes[4-8 & 20-24] are all NULL, I see this apparent in my char array. The array reads as follows {4 bytes of BASEID_Code, 4 NULL bytes, 8 bytes of zeroed padding, 4 bytes of

问题 I have a query that's written dynamically (OO PHP via Joomla) to insert some values into a MySQL database. The form that a user fills out has a field on it for dollar amount, and if they leave that blank I want the value going into the system to be NULL. I've written out the query to the error log as it's running; this is what the query looks like: INSERT INTO arrc_Voucher (VoucherNbr,securityCode,sequentialNumber, TypeFlag, CreateDT, ActivatedDT, BalanceInit, BalanceCurrent, clientName)

问题 I know there's an old saying when you want to indicate this specific pointer doesn't point to anything it should be set to NULL(actually 0), but I'm wondering isn't there actually a physical part of memory with the address of NULL(0) ? 回答1: There is always a physical address of 0 (but it may not necessarily map onto physical RAM), but on a typical platform any accesses will typically be performed in a virtual address space (as jweyrich points out below, you can use mmap and so on to directly

问题 Does the following snippet compile/execute the block in the if-statement? int* pointer = NULL; int deref = *pointer; if(deref == NULL){ // will execute? } Since the pointer variable contains NULL does the dereference of this pointer variable also return NULL or will this result in a runtime error? 回答1: The result is "undefined behaviour", which may or may not trigger a runtime error, and should in any case always be avoided. 回答2: Once you set: int* pointer = NULL; pointer points to nothing.

问题 i am trying to execute the records that have TotalTime null value from the table NewTimeAttendance ... TotalTime datatype nchar(10) select * from newtimeattendance where TotalTime = 'NULL' ....nothing select * from newtimeattendance where TotalTime = 'null' ....nothing select * from newtimeattendance where TotalTime = 'Null' ....nothing select * from newtimeattendance where TotalTime = null ....nothing select * from newtimeattendance where TotalTime = Null ....nothing select * from

问题 This question already has answers here : C# Events and Thread Safety (15 answers) Closed 6 years ago . I have seen various coding styles to fire events in C#. The first style consisting of the following: -an event handler public delegate void NumberReachedEventHandler(object sender, NumberReachedEventArgs e); -an event public event NumberReachedEventHandler NumberReached; -and the method to fire the event protected virtual void OnNumberReached(NumberReachedEventArgs e) { if(NumberReached !=

问题 From the import documentation of BigQuery, Note: Null values are not allowed So I assume null is not allowed in a json-formatted data for BigQuery import. However, null value is actually very common in regular ETL task (due to missing data). What should be a good solution to import such json source files? Note my data contains nested structures so I do not prefer a conversion to CSV and use ,, to represent a null value. One way I think I can do is to replace all null values with default

问题 Is there an idiom in Kotlin for setting a variable to null if it is not already null? Something more semantically pleasing than: var test: String? = null if(test != null) test = null 回答1: You can use the execute if not null idiom: test?.let { test = null } 回答2: Just assign null to local variable: test = null In case if it's not null - you assign null to this variable. In case if variable is null - you just assign null to it, so nothing changed. 回答3: I came up with this extensions which makes

问题 When I run this program in NUnit I get an error Object reference not set to an instance of an object. Though this is not the original program I get a similar error there too. Any help appreciated. Exception occurs at driver.Navigate().GoToUrl("http://www.yahoo.com/"); Program: using System; using System.Collections.Generic; using System.Linq; using System.Text; using NUnit.Framework; using OpenQA.Selenium.Firefox; using OpenQA.Selenium; namespace Class_and_object { [TestFixture] public class

问题 I search for answer all day long, but when i try to get the table layout i am having null. I found info that it may be another table layout with same name, but there is only one. My .xml file : my xml and my code is here layout6 = (TableLayout)findViewById(R.id.shdslResultsTableLayout); layout6.setVisibility(0); always ends up with null pointer. Please help. 回答1: If findViewById() is returning a NPE, try some of these: Clean the project via Project -> Clean... -> check your project -> OK