build/pymake/README@141e0f1194b1 (annotated)
build/pymake/README
Wed, 31 Dec 2014 07:16:47 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Wed, 31 Dec 2014 07:16:47 +0100
- branch
- TOR_BUG_9701
- changeset 3
- 141e0f1194b1
- permissions
- -rw-r--r--
Revert simplistic fix pending revisit of Mozilla integration attempt.
| michael@0 | 1 | INTRODUCTION |
| michael@0 | 2 | |
| michael@0 | 3 | make.py (and the pymake modules that support it) are an implementation of the make tool |
| michael@0 | 4 | which are mostly compatible with makefiles written for GNU make. |
| michael@0 | 5 | |
| michael@0 | 6 | PURPOSE |
| michael@0 | 7 | |
| michael@0 | 8 | The Mozilla project inspired this tool with several goals: |
| michael@0 | 9 | |
| michael@0 | 10 | * Improve build speeds, especially on Windows. This can be done by reducing the total number |
| michael@0 | 11 | of processes that are launched, especially MSYS shell processes which are expensive. |
| michael@0 | 12 | |
| michael@0 | 13 | * Allow writing some complicated build logic directly in Python instead of in shell. |
| michael@0 | 14 | |
| michael@0 | 15 | * Allow computing dependencies for special targets, such as members within ZIP files. |
| michael@0 | 16 | |
| michael@0 | 17 | * Enable experiments with build system. By writing a makefile parser, we can experiment |
| michael@0 | 18 | with converting in-tree makefiles to another build system, such as SCons, waf, ant, ...insert |
| michael@0 | 19 | your favorite build tool here. Or we could experiment along the lines of makepp, keeping |
| michael@0 | 20 | our existing makefiles, but change the engine to build a global dependency graph. |
| michael@0 | 21 | |
| michael@0 | 22 | KNOWN INCOMPATIBILITIES |
| michael@0 | 23 | |
| michael@0 | 24 | * Order-only prerequisites are not yet supported |
| michael@0 | 25 | |
| michael@0 | 26 | * Secondary expansion is not yet supported. |
| michael@0 | 27 | |
| michael@0 | 28 | * Target-specific variables behave differently than in GNU make: in pymake, the target-specific |
| michael@0 | 29 | variable only applies to the specific target that is mentioned, and does not apply recursively |
| michael@0 | 30 | to all dependencies which are remade. This is an intentional change: the behavior of GNU make |
| michael@0 | 31 | is neither deterministic nor intuitive. |
| michael@0 | 32 | |
| michael@0 | 33 | * $(eval) is only supported during the parse phase. Any attempt to recursively expand |
| michael@0 | 34 | an $(eval) function during command execution will fail. This is an intentional incompatibility. |
| michael@0 | 35 | |
| michael@0 | 36 | * There is a subtle difference in execution order that can cause unexpected changes in the |
| michael@0 | 37 | following circumstance: |
| michael@0 | 38 | ** A file `foo.c` exists on the VPATH |
| michael@0 | 39 | ** A rule for `foo.c` exists with a dependency on `tool` and no commands |
| michael@0 | 40 | ** `tool` is remade for some other reason earlier in the file |
| michael@0 | 41 | In this case, pymake resets the VPATH of `foo.c`, while GNU make does not. This shouldn't |
| michael@0 | 42 | happen in the real world, since a target found on the VPATH without commands is silly. But |
| michael@0 | 43 | mozilla/js/src happens to have a rule, which I'm patching. |
| michael@0 | 44 | |
| michael@0 | 45 | * pymake does not implement any of the builtin implicit rules or the related variables. Mozilla |
| michael@0 | 46 | only cares because pymake doesn't implicitly define $(RM), which I'm also fixing in the Mozilla |
| michael@0 | 47 | code. |
| michael@0 | 48 | |
| michael@0 | 49 | ISSUES |
| michael@0 | 50 | |
| michael@0 | 51 | * Speed is a problem. |
| michael@0 | 52 | |
| michael@0 | 53 | FUTURE WORK |
| michael@0 | 54 | |
| michael@0 | 55 | * implement a new type of command which is implemented in python. This would allow us |
| michael@0 | 56 | to replace the current `nsinstall` binary (and execution costs for the shell and binary) with an |
| michael@0 | 57 | in-process python solution. |
| michael@0 | 58 | |
| michael@0 | 59 | AUTHOR |
| michael@0 | 60 | |
| michael@0 | 61 | Initial code was written by Benjamin Smedberg <benjamin@smedbergs.us>. For future releases see |
| michael@0 | 62 | http://benjamin.smedbergs.us/pymake/ |
| michael@0 | 63 | |
| michael@0 | 64 | See the LICENSE file for license information (MIT license) |
