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65 lines
2.7 KiB
Plaintext
65 lines
2.7 KiB
Plaintext
INTRODUCTION
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make.py (and the pymake modules that support it) are an implementation of the make tool
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which are mostly compatible with makefiles written for GNU make.
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PURPOSE
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The Mozilla project inspired this tool with several goals:
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* Improve build speeds, especially on Windows. This can be done by reducing the total number
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of processes that are launched, especially MSYS shell processes which are expensive.
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* Allow writing some complicated build logic directly in Python instead of in shell.
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* Allow computing dependencies for special targets, such as members within ZIP files.
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* Enable experiments with build system. By writing a makefile parser, we can experiment
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with converting in-tree makefiles to another build system, such as SCons, waf, ant, ...insert
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your favorite build tool here. Or we could experiment along the lines of makepp, keeping
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our existing makefiles, but change the engine to build a global dependency graph.
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KNOWN INCOMPATIBILITIES
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* Order-only prerequisites are not yet supported
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* Secondary expansion is not yet supported.
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* Target-specific variables behave differently than in GNU make: in pymake, the target-specific
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variable only applies to the specific target that is mentioned, and does not apply recursively
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to all dependencies which are remade. This is an intentional change: the behavior of GNU make
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is neither deterministic nor intuitive.
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* $(eval) is only supported during the parse phase. Any attempt to recursively expand
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an $(eval) function during command execution will fail. This is an intentional incompatibility.
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* There is a subtle difference in execution order that can cause unexpected changes in the
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following circumstance:
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** A file `foo.c` exists on the VPATH
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** A rule for `foo.c` exists with a dependency on `tool` and no commands
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** `tool` is remade for some other reason earlier in the file
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In this case, pymake resets the VPATH of `foo.c`, while GNU make does not. This shouldn't
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happen in the real world, since a target found on the VPATH without commands is silly. But
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mozilla/js/src happens to have a rule, which I'm patching.
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* pymake does not implement any of the builtin implicit rules or the related variables. Mozilla
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only cares because pymake doesn't implicitly define $(RM), which I'm also fixing in the Mozilla
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code.
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ISSUES
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* Speed is a problem.
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FUTURE WORK
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* implement a new type of command which is implemented in python. This would allow us
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to replace the current `nsinstall` binary (and execution costs for the shell and binary) with an
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in-process python solution.
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AUTHOR
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Initial code was written by Benjamin Smedberg <benjamin@smedbergs.us>. For future releases see
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http://benjamin.smedbergs.us/pymake/
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See the LICENSE file for license information (MIT license)
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