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