Das Build

A generic Build System Driven by GNU Make

Introduction

A little over a year ago I started getting really sick of duplicating the same boiler-plate structure for every project Makefile that I was working on.

Around that time I also started running into issues with dropping library code into another project and having to twiddle the build systems of each for the project to build properly.

Prompted by the desire to quickly develop C/C++ code without the grief of stopping every few hours to add extra stuff into a Makefile, I decided to solve the problem for myself.

What you see here is the second attempt at these goals.

Features

• Flat-make building strategy - All dependencies are calculated by a single instance of GNU Make. This avoids quite a few problems endemic with recursive build strategies.
• Minimal boilerplate for program dependencies. You specify the name of the program or library that is your target, along with the list of source files you wish to be be built as part of it, and DasBuild does the rest.
• Ability to specify per-source, per-program and debug/coverage specific build flags.
• Integration with the gtest unit test framework.
• Ability to separately drive builds of external dependencies in a manner similar to OpenEmbedded's BitBake distribution building utility. This is nowhere near as sophisticated as BitBake, but anyone familiar with that tool will immediately feel at home.
• Ability to generate code coverage reports.
• Build from any source directory and the build system will figure out what you mean and what needs to be rebuilt!

Getting started

Let's start with a basic example of a project, the tired old Hello World example; lets assume that you have the following project hierarchy:

• proj/
  • hello.cc

If you 'git clone' DasBuild into your project, so that you now have:

• proj/
  • DasBuild/
  • hello.cc

Then create a 'proj/Makefile' with the following content:

TARGETS = hello
hello.SRC = hello.cc

ifndef TOPDIR
  TOPDIR = .
  include $(TOPDIR)/DasBuild/Makefile.main
endif

You now have a complete makefile, with all the bells and whistles of clean, debug unit test targets and the like.

Adding a Library to Your Project

Let's now imagine that we have a 'libsalutation' that we wish to integrate into our hello application. We'd like this library to be a standalone static library that gets linked into our hello program, and as such our source code organization now looks something like this:

• proj/
  • DasBuild/
  • Makefile
  • salutation/
    • german.cc
    • swahili.cc
  • hello.cc

We have three tasks to accomplish:

1. Inform make that there's stuff to look for in the 'salutation' directory.
2. Specify how libsalutation will be built.
3. Make the salutation library a dependency of 'hello'

It is rather easy to do this by creating a Makefile in the 'salutation' directory with the following content:

LIB_TARGETS = salutation
salutation.SRC = german.cc swahili.cc

ifndef TOPDIR
  TOPDIR = ..
  include $(TOPDIR)/DasBuild/Makefile.subdir
endif

This defines our library build. Now let's look at what the top-level Makefile looks like:

SUBDIRS = salutation
TARGETS = hello
hello.SRC = hello.cc
hello.LIBDEP = salutation

ifndef TOPDIR
  TOPDIR = .
  include $(TOPDIR)/DasBuild/Makefile.main
endif

That's all!

Variables

These variables provide ways of modifying the build system's behavior.

Overridable Programs

• AR - Static library archiver - default is 'ar'.
• BROWSER - Web browser to launch for report targets - default is 'chromium-browser'.
• CC - The C compiler to use - default value is 'gcc'.
• CXX - The C++ compiler to use - default value is 'g++'.
• RAGEL - Ragel state machine compiler - default is 'ragel'.
• OBJCPY - The objcpy program to use - default is 'objcopy'.
• RANLIB - The static library indexer - default is 'ranlib -D'

Changing behavior

• V - Specifying V=1 on the command line will allow you to see the commands executed rather than the terse build output; this is useful for debugging builds.
• VENDOR_UNIT_TEST - Setting this to '1' on the command line will cause the 'check' step of vendor builds to run.