Methods, systems, and apparatus, including computer programs encoded on computer storage media, for automatically determining configuration properties of a compiler. One of the methods includes determining that an executable of the newly created process is a compiler called by the build system to compile source code of a source code file. In response to the determining, a plurality of configuration properties of the compiler called by the build system are determined, the configuration properties including first properties of a plurality of built-in functions of the compiler, second properties of a plurality of built-in types of the compiler, or both. A compiler emulator is configured to emulate the behavior of the compiler called by the build system using the determined configuration properties. Access to the source code is provided to the compiler emulator configured using the determined configuration properties.