Why are my Custom Build steps not running in Visual Studio?

The reason it's failing is that there's another custom build step in the same project that's calling a batch file, like this:

Command Line: buildsomething.bat something.h
Description: Building something
Outputs: something.h

As of Visual Studio 2010, all the custom build commands are concatenated into a single batch file, which is then executed. When a batch file runs another batch file, Windows doesn't return control to the first batch file. It's like a goto, not a function call. So to fix the problem, you need to use call like this:

Command Line: call buildsomething.bat something.h

call makes the flow of control return to Visual Studio's batch file, and hence lets your other Custom Build steps run.

_{(I'm answering my own question so that future searchers can find the answer.)}