ATBG: null coalescing precedence

In the latest episode of the Coverity Development Testing Blog‘s continuing series “Ask the Bug Guys”, I dig into two questions about the null coalescing operator. This handy little operator is probably the least well understood of all the C# operators, but it is quite useful. Unfortunately, it is easy to accidentally use it incorrectly due to precedence issues.

As always, if you have questions about a bug you’ve found in a C, C++, C# or Java program that you think would make a good episode of ATBG, please send your question along with a small reproducer of the problem to We cannot promise to answer every question or solve every problem, but we’ll take a selection of the best questions that we can answer and address them on the dev testing blog every couple of weeks.


Precedence vs order redux

Once more I’m revisting the myth that order of evaluation has any relationship to operator precedence in C#. Here’s a version of this myth that I hear every now and then. Suppose you’ve got a field arr that is an array of ints, and some local variables index and value: Continue reading

C++ and the pit of despair

Raymond has an interesting post today about two subtle aspects of C#: how order of evaluation in an expression is specified as strictly left-to-right, and how the rules regarding local shadowing ensure that an identifier has exactly one meaning in a local scope. He makes an educated guess that the reason for these sorts of rules is to “reduce the frequency of a category of subtle bugs“.

I’d like to take this opportunity to both confirm that guess and to expand upon it a bit. Continue reading