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A small python based build file generator targeting ninja

Project description

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pyrate

pyrate is a small python based build file generator targeting ninja(s).

It allows to describe the build process of small projects in a very simple way using a python based configuration file. This description is then turned into ninja build files, that enable a very quick turnaround of project builds.

Quick HOWTO

The following presents the necessary steps to quickly test the waters with this tool (assuming ninja is already installed). These commands will install pyrate, generate the ninja build file, build and execute a small executable:

pip install pyrate-build
echo -e '#include <cstdio>\nint main() { printf("Ahoy World!"); return 0; }' > test.cpp
echo -e "executable('test', 'test.cpp')" > build.py
pyrate
ninja
./test

Installation

pyrate is very easy to deploy - there are no particular installation steps to use it once the single script pyrate.py is available somewhere. It can even board the project directory of your project and simply get called from there. The only dependency to generate the ninja build files is having a working python installation. pyrate should work out of the box with all python versions between 2.4 and 3.4. To actually build the project, ninja has to be installed as well.

The latest release version of pyrate can be installed from the Python Package Index with:

pip install pyrate-build

The latest development version can be retrieved from the github repository:

git clone https://github.com/pyrate-build/pyrate-build

Usage

The quickest way to execute pyrate is:

pyrate

Without any parameters, pyrate will use the build configuration script (pyrate script) named build.py and create a ninja build file called build.ninja. If another pyrate script should be used, this can be specified as a positional argument. The name of the created ninja build file can be customized using the option -o or --output. The quick invocation shown above is therefore equivalent to the following invocation:

pyrate --output mybuild.ninja mybuild.py

When the script is started, it first changes the current directory to the directory containing the build configuration script, so all path names are relative to it.

pyrate path/to/mybuild.py

will therefore create the ninja build file path/to/build.ninja

If pyrate is placed in a directory listed in the PATH environment variable (as automatically done by pip install pyrate-build), the build configure script can be made executable to invoke pyrate automatically by starting the build config script with:

#!/usr/bin/env pyrate

Build File Configuration Syntax

The build configuration for pyrate is written in python - so the full power of python can be used to construct and describe the build process. Several classes, functions and variables are available to ease and customize the configuration of the build process.

Specifying build input

In general, a build input list that can be used to construct a build target takes the form:

  • [<item1>, <item2>, ...]

Each item can be one of the following:

  • a string is interpreted as a file name that is processed according to the rules specified by the packages in the compiler dictionary
  • a build target as returned by the functions described in Defining build targets or explicitly defined
  • an external dependency as returned by the functions described in External dependencies or explicitly defined
  • or any other kind of BuildSource (explained later)

Instead of a list, it is also possible to specify a space separated string of file names. Such a string is automatically split, so the following two build input lists behave identically:

  • "<file1> <file2> ..."
  • ['<file1>', '<file2>', ...]

Besides specifying file names by hand, there are many ways to get a list of files. Common methods include calling the python function os.listdir or using the helper function match provided by pyrate:

  • match(selector, dir_name = '.')

This functions allows to select files from a directory using a string consisting of black / white listing path name patterns. The selector '*.cpp -test*.cpp test3.cpp *.h' for example selects all files ending with ‘.h’ and ‘.cpp’, with the exception of those ‘.cpp’ files that start with ‘test’ and are not called ‘test3.cpp’.

Defining build targets

There are four global helper functions to define object files, executables and libraries based on a list of build inputs (which can be files, other targets or externals - as shown in Specifying build input):

  • executable(name, input_list, compiler_opts = None, linker_opts = None)
  • shared_library(name, input_list, compiler_opts = None, linker_opts = None)
  • static_library(name, input_list, compiler_opts = None, linker_opts = None)
  • object_file(name, input_list, compiler_opts = None)

Each function returns a build target object, that can be used as input / dependency of another function. If multiple executables / libraries or object files with the same name but different inputs / options are defined, pyrate will ensure that the output will have a unique name (by appending a hash based suffix as needed). More details about this is available in Target Collision Avoidance.

These functions exist as global functions and as member functions of a so-called build context, that describes how these functions are processed. The global functions are just executing within the default build context.

By default, all build targets that are defined by the above functions (or direct API calls) are built. In order to select only certain default targets, the global variable default_targets can be used:

  • default_targets = [<target>,...] (list of targets), <target> (single target) or None (all targets are built)

External dependencies

The build environment / dependencies on external packages can be expressed using the following functions / variables:

  • find_external(name, ...)

The function find_external searches for some external dependency (built-in, pkg-config package or self-defined) with the given name and returns either None or a representation of the dependency. The function takes additional positional and keyword arguments that depend on the external package. A common argument for this function is a version selector, that is supplied through a global variable:

  • version

The comparison between this variable (eg. version >= 4.1) and a version specifier will return a function that can be used to check the expression and is used by the external package finder. A version specifier can be a string ('0.1.2') or tuple ((0, 1, 2)) with an arbitrary number of subversion separators, or a floating point number (1.2). This allows for example to write find_external('clang', version >= 3.5) to discover a clang installation with version 3.5 or later.

Since find_external also integrates with pkg-config, a large number of external packages is available - in addition to a handful of builtin external packages with special implementation features. It is also possible to add new packages that are recognized. A list of the builtin packages is presented in Externals.

In order to simplify the creation of external packages that already provide a build configuration tool to query version, linker or compiler options, pyrate provides the function:

  • create_external(name, build_helper, ...)

It requires the user to define a name for the external package and to supply the build configuration tool. The values of additional parameters are interpreted as command line options for the build configuration tool. The name of these additional parameters specify the name of the rule that gets supplied with the flags given by the output of the build configuration tool. However there are four parameters that have a special meaning:

  • version_query - similar to the other parameters, the value of this parameter is used as build configuration tool option to determine the current version of the external package. As a consequence of providing this option, the resulting external package will support the parameter version.
  • version_parser - this parameter allows to supply a function that parses the version string provided by the build configuration tool and is only used if version_query is given.
  • version - specifies required version (eg. version = version >= 11.5) and can only be used if version_query is given
  • link = opts is equivalent to specifying link_shared = opts, link_static = opts and link_exe = opts

The following example recreates the builtin external package for wxWidgets:

my_wxwidgets = create_external('wxwidgets', build_helper = 'wx-config',
    version_query = '--version', link = '--libs', compile_cpp = '--cxxflags')

Configuration of the build environment

A build context allows for example to define implicit dependencies that are automatically included in all generated object files, executables or libraries. An instance of such a build context is created with:

  • Context(...) - the most important parameters are:
    • implicit_input, implicit_object_input, implicit_static_library_input, implicit_shared_library_input and implicit_executable_input

The default context used by the global functions presented in Defining build targets can be set using the variable:

  • default_context = Context(...)

Finally, the used default compilers can be configured via the global variable

  • compiler

This is a dictionary that contains links to external packages that provide the basic rules and parameters that are used to build the source. This dictionary can be modified, but should not be overwritten.

It is possible to query the current version of pyrate via the variable:

  • pyrate_version

this allows to ensure a compatible version of pyrate with something along the lines of:

assert(pyrate_version > '0.1.8')

Target Collision Avoidance

As explained in Defining build targets, pyrate will always ensure that targets with different inputs / options but same name will generate different output files (by appending a hash based suffix as needed). However it is possible to switch off the renaming of colliding targets for a unique target. Beware: Having two different targets that switch off the renaming with the option no_rename = True will abort the build file generation. The following build configuration file:

ex1 = executable('example.bin', 'test.cpp', compiler_opts = '-O1')
ex2 = executable('example.bin', 'test.cpp', compiler_opts = '-O2')
ex3 = executable('example.bin', 'test.cpp', compiler_opts = '-O3')
ex4 = executable('example.bin', 'test.cpp', compiler_opts = '-O2', no_rename = True)
print('hash(ex1) = %s' % ex1.get_hash())
print('hash(ex2) = %s' % ex2.get_hash())
print('hash(ex3) = %s' % ex3.get_hash())
print('hash(ex4) = %s' % ex4.get_hash())

will result (for example in an linux environment) in the generation of three object files named test_<hash1>.o, test_<hash2>.o, test_<hash3>.o, since there are only three different settings used during the compilation of test.cpp. During the linking step, these object files will generate three binaries named example.bin, example_<hash4>.bin, example_<hash5>.bin. Where example.bin was compiled with the compiler option ‘-O2’. To identify which target belong to which hash, the <target_obj>.get_hash() function can be used.

However it is strongly recommended to always ensure collision free names for executables and shared / static libraries.

Externals

Currently the following builtin externals are supported (listed with all possible find_external arguments):

  • gcc
    • version - specifies required version (eg. version >= 5.2)
    • std - C/C++ language standard version (eg. 'gnu++14' or 'latest'). A property with the same name allows to also set this value on an existing external (eg. compiler['C++'].std = 'latest').
    • compile_cpp - name of the executable
    • compile_cpp_opts - options that are used during the compilation stage
    • link_static_opts, link_shared_opts, link_exe_opts - options that are used during the linking stage
  • clang
    • version - specifies required version (eg. version > 3.5)
    • std - C/C++ language standard version (eg. 'c++1y' or 'latest'). A property with the same name allows to also set this value on an existing external (eg. compiler['C++'].std = 'latest').
    • compile_cpp - name of the executable
    • compile_cpp_opts - options that are used during the compilation stage
    • link_static_opts, link_shared_opts, link_exe_opts - options that are used during the linking stage
  • swig - The swig package also provides the member function wrapper to describe the generation of automated interface code
    • version - specifies required version (eg. version > '3.0.2')
    • wrapper(target_language, library_name, interface_filename, libs = [<targets>...])
  • pthread - posix thread library

The following list contains all builtin externals with a single find_external parameter version, that specifies the required version (eg. version >= 2.6):

  • fltk - FLTK GUI Library
  • llvm - LLVM compiler infrastructure libraries
  • odbc - Open Database Connectivity middleware
  • root - Library for large scale data analysis
  • wx - wxWidgets GUI Toolkit

Many more externals are available through the integration with pkg-config. The full list of available packages on a system can be queried with:

pkg-config --list-all

All packages listed in that overview can be accessed with the find_external function.

Example

The basic pyrate build configuration file for a simple C++ project with a single source file producing a single executable looks like this:

executable('test', ['test.cpp'])

A more complicated example is presented in the following code fragment. It demonstrates how to

  • change the default compiler to clang,
  • define a native static and dynamic library from a set of files selected by wildcards,
  • generate several executables accessing to the shared library and
  • generate a wrapper library to access the C++ library from python (if swig is available).
clang = find_external('clang', version >= 3.7, std = 'c++11')
if clang:
    compiler['C++'] = clang

lib_files = match("*.cpp -test* -mylib.cpp")
static_library('libFoo', lib_files, compiler_opts = '-O3')
lib_reference = shared_library('libFoo', lib_files)

python = find_external('python', version > 2)
swig = find_external('swig')
if swig and python:
    swig.wrapper('python', 'mylib', 'mylib.i', libs = [lib_reference])

for fn in match("test*.cpp"):
    executable(fn.replace('.cpp', '.exe'), [fn, lib_reference])

Many more examples with an increasing level of complexity are available in the github repository.

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