How can I run custom tools from a premake build script?

Question

I'm using protocol buffers for data serialization in my C++ application. I would like to add the invokation of the protoc code generator in my premake build script (thus ensure the up-to-date state of the generated classes and avoid the need to store generated source under version control).

Even their FAQ has a question and answer about this, but the answer is very incomplete for me. Having the ability to call any lua function is great, but where exactly do I put that call? I need to run the protoc compiler before building either the application or the unit tests.

Answer 1

You can certainly call outside code from Premake scripts. But remember: Premake scripts are used to generate build files: Makefiles, C++ projects, etc. The Premake script is run before building the project.

If you want this preprocess to be run outside of the actual build files (and not by make, VC++, Code::Blocks, etc), then it's easy. Lua's os.execute will execute a command-line.

Premake scripts are still Lua scripts. All of the Premake commands are just Lua calls into functions that Premake defines. Premake executes the scripts, then uses the data from them to generate the build files. So all of your Lua code is run during the execution of the script. Where you put this command in your script is irrelevant; wherever it is, it will execute before your build files are generated.

Answer 2

And if you want to run the protoc step during the build (from VC++, makefile, etc.) you can set up a prebuild command. See http://industriousone.com/prebuildcommands for more info and an example.