pymake A mostly GNU-compatible python implementation of `make`

(Now maintained by the Mozilla community.)

Download Now

Latest sources: Whatever I happen to have pushed last. Nowadays it tends to be pretty stable.
Code repository: For browsing, and also for pulling using Mercurial.

About

make.py (and the pymake modules that support it) are an implementation of the make tool which are mostly compatible with makefiles written for GNU make. For more information about building Mozilla using pymake, see the Mozilla Developer Center docs.

Purpose

The Mozilla project inspired this tool with several goals:

Improve build speeds, especially on Windows. This can be done by reducing the total number of processes that are launched, especially MSYS shell processes which are expensive.
Allow writing some complicated build logic directly in Python instead of in shell.
Allow computing dependencies for special targets, such as members within ZIP files.
Enable experiments with build system. By writing a makefile parser, we can experiment with converting in-tree makefiles to another build system, such as SCons, waf, ant, ...insert your favorite build tool here. Or we could experiment along the lines of makepp, keeping our existing makefiles, but change the engine to build a global dependency graph.

Known Incompatibilities

Order-only prerequisites are not supported.
Target-specific variables behave differently than in GNU make: in pymake, the target-specific variable only applies to the specific target that is mentioned, and does not apply recursively to all dependencies which are remade. This is an intentional change: the behavior of GNU make is neither deterministic nor intuitive.
On Windows, Mozilla builds correctly, but many other MSYS-based projects will not. This is because pymake is not a native MSYS program, and does not recognize MSYS-style paths.
There is a subtle difference in execution order that can cause unexpected changes in the following circumstance:
- A file foo.c exists on the VPATH
- A rule for foo.c exists with a dependency on sometool and no commands
- sometool is remade for some other reason earlier in the file
In this case, pymake resets the vpath resolution of foo.c, while GNU make does not. This shouldn't happen in the real world, since a target found on the VPATH without commands is silly. But mozilla/js/src happens to have a rule, which I'm patching.
pymake does not implement any of the builtin implicit rules or the related variables. Mozilla only cares because pymake doesn't implicitly define $(RM), which I'm also fixing in the Mozilla code.

Issues

Parsing is currently very slow compared to GNU make, to the point where the overhead is noticeable. I would love help implementing a parsing system using mxTextTools instead of Python regular expressions, which would be much more efficient. Note that on Windows pymake is still a net improvement for building Mozilla, because of the insane overhead of launching processes on Windows.

Future Work

Author

Initial code was written by Benjamin Smedberg. The code is now maintained by the Mozilla community, primarily Ted Mielczarek and Kyle Huey.

License

MIT license. See the LICENSE file.