Deleting elements from an JavaScript array and closing up the gaps

August 18, 2014 Aug 18, 2014 08/18/14

Raymond Chen

Today's Little Program is an exercise that solves the following problem: Given a JavaScript array a and an unsorted array indices (possibly containing duplicates), calculate the result of deleting all of the elements from the original array as specified by the indices. For example, suppose a = ["alice", "bob", "charles", "david", "eve"] ...

The scope of the C# checked/unchecked keyword is static, not dynamic

August 15, 2014 Aug 15, 2014 08/15/14

Raymond Chen

C# has operators checked and unchecked to control the behavior of the language in the face of integer overflow. There are also checked and unchecked statements which apply the behavior to blocks of statements rather than single expressions. Why, then, doesn't this code below raise an overflow exception? (Mini-exercise: Why couldn't I ...

Customers not getting the widgets they paid for if they click too fast -or- In C#, the += operator is not merely not guaranteed to be atomic, it is guaranteed not to be atomic

August 14, 2014 Aug 14, 2014 08/14/14

Raymond Chen

In the C# language, operation/assignment such as += are explicitly not atomic. But you already knew this, at least for properties. Recall that properties are syntactic sugar for method calls. A property declaration is internally converted to the equivalent of Accessing a property is similarly transformed. Note that the only ...

Keep your eye on the code page: C# edition (the mysterious third code page)

August 13, 2014 Aug 13, 2014 08/13/14

Raymond Chen

A customer was having trouble manipulating the console from a C# program: We found that C# can read only ASCII data from the console. If we try to read non-ASCII data, we get garbage. Observe that this program is unable to read the Å and ö characters. They come back as garbage. Although there are three code pages that have...

Keep your eye on the code page: C# edition (warning about DllImport)

August 12, 2014 Aug 12, 2014 08/12/14

Raymond Chen

Often, we receive problem reports from customers who failed to keep their eye on the code page. Does the SH­Get­File­Info function support files with non-ASCII characters in their names? We find that the function either fails outright or returns question marks when asked to provide information for files with non-ASCII ...

If you want to set a thread's apartment model via Thread.CurrentThread.ApartmentState, you need to act quickly

August 11, 2014 Aug 11, 2014 08/11/14

Raymond Chen

Welcome to CLR Week 2014. Don't worry, it'll be over in a few days. A customer wanted to know why their Folder­Browser­Dialog was displaying the infamous Current thread must be set to single thread apartment (STA) mode before OLE calls can be made error. "Even though we set the Apartment­State to STA, the apartment state is ...

The case of the orphaned LpdrLoaderLock critical section

August 8, 2014 Aug 8, 2014 08/8/14

Raymond Chen

A customer found that under heavy load, their application would occasionally hang. Debugging the hang shows that everybody was waiting for the Lpdr­Loader­Lock critical section. The catch was that the critical section was reported as locked, but the owner thread did not exist. How can a critical section be owned by thread that no ...