1. A computer implemented method for automatically persisting variable data, the method being performed by a computer system, comprising a compiler, at a time of compiling source code for an application, the method comprising: at compile time, using the compiler to perform operations comprising: prior to compiling the source code of the application into an executable file, identifying, by the computer system, a variable in the source code of the application that is declared with a predefined keyword, the predefined keyword indicating that the variable in the source code of the application should be persistent; and generating the executable file for the application from the source code, wherein generating the executable file comprises: compiling the source code for the application into runtime code for executing the application, wherein compiling the source code for the application includes generating, by the compiler and in response to the identified variable, particular runtime code for the source code of the application for each instance in the source code where the corresponding identified variable occurs, wherein the generated particular runtime code, distinct from the runtime code of the application, is incorporated into the executable file for the application and is configured to provide the persistence of the variable of the application, and wherein execution of the runtime code for the application that provides the persistence during execution of the executable file saves data assigned to the variable in a nonvolatile data store, and outputting the executable file for the application that includes the generated runtime code.