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diff --git a/Doc/library/packaging.compiler.rst b/Doc/library/packaging.compiler.rst new file mode 100644 index 0000000000..d77197283d --- /dev/null +++ b/Doc/library/packaging.compiler.rst @@ -0,0 +1,677 @@ +:mod:`packaging.compiler` --- Compiler classes +============================================== + +.. module:: packaging.compiler + :synopsis: Compiler classes to build C/C++ extensions or libraries. + + +This subpackage contains an abstract base class representing a compiler and +concrete implementations for common compilers. The compiler classes should not +be instantiated directly, but created using the :func:`new_compiler` factory +function. Compiler types provided by Packaging are listed in +:ref:`packaging-standard-compilers`. + + +Public functions +---------------- + +.. function:: new_compiler(plat=None, compiler=None, verbose=0, dry_run=0, force=0) + + Factory function to generate an instance of some + :class:`~.ccompiler.CCompiler` subclass for the requested platform or + compiler type. + + If no argument is given for *plat* and *compiler*, the default compiler type + for the platform (:attr:`os.name`) will be used: ``'unix'`` for Unix and + Mac OS X, ``'msvc'`` for Windows. + + If *plat* is given, it must be one of ``'posix'``, ``'darwin'`` or ``'nt'``. + An invalid value will not raise an exception but use the default compiler + type for the current platform. + + .. XXX errors should never pass silently; this behavior is particularly + harmful when a compiler type is given as first argument + + If *compiler* is given, *plat* will be ignored, allowing you to get for + example a ``'unix'`` compiler object under Windows or an ``'msvc'`` compiler + under Unix. However, not all compiler types can be instantiated on every + platform. + + +.. function:: customize_compiler(compiler) + + Do any platform-specific customization of a CCompiler instance. Mainly + needed on Unix to plug in the information that varies across Unices and is + stored in CPython's Makefile. + + +.. function:: gen_lib_options(compiler, library_dirs, runtime_library_dirs, libraries) + + Generate linker options for searching library directories and linking with + specific libraries. *libraries* and *library_dirs* are, respectively, lists + of library names (not filenames!) and search directories. Returns a list of + command-line options suitable for use with some compiler (depending on the + two format strings passed in). + + +.. function:: gen_preprocess_options(macros, include_dirs) + + Generate C preprocessor options (:option:`-D`, :option:`-U`, :option:`-I`) as + used by at least two types of compilers: the typical Unix compiler and Visual + C++. *macros* is the usual thing, a list of 1- or 2-tuples, where ``(name,)`` + means undefine (:option:`-U`) macro *name*, and ``(name, value)`` means + define (:option:`-D`) macro *name* to *value*. *include_dirs* is just a list + of directory names to be added to the header file search path (:option:`-I`). + Returns a list of command-line options suitable for either Unix compilers or + Visual C++. + + +.. function:: get_default_compiler(osname, platform) + + Determine the default compiler to use for the given platform. + + *osname* should be one of the standard Python OS names (i.e. the ones + returned by ``os.name``) and *platform* the common value returned by + ``sys.platform`` for the platform in question. + + The default values are ``os.name`` and ``sys.platform``. + + +.. function:: set_compiler(location) + + Add or change a compiler + + +.. function:: show_compilers() + + Print list of available compilers (used by the :option:`--help-compiler` + options to :command:`build`, :command:`build_ext`, :command:`build_clib`). + + +.. _packaging-standard-compilers: + +Standard compilers +------------------ + +Concrete subclasses of :class:`~.ccompiler.CCompiler` are provided in submodules +of the :mod:`packaging.compiler` package. You do not need to import them, using +:func:`new_compiler` is the public API to use. This table documents the +standard compilers; be aware that they can be replaced by other classes on your +platform. + +=============== ======================================================== ======= +name description notes +=============== ======================================================== ======= +``'unix'`` typical Unix-style command-line C compiler [#]_ +``'msvc'`` Microsoft compiler [#]_ +``'bcpp'`` Borland C++ compiler +``'cygwin'`` Cygwin compiler (Windows port of GCC) +``'mingw32'`` Mingw32 port of GCC (same as Cygwin in no-Cygwin mode) +=============== ======================================================== ======= + + +.. [#] The Unix compiler class assumes this behavior: + + * macros defined with :option:`-Dname[=value]` + + * macros undefined with :option:`-Uname` + + * include search directories specified with :option:`-Idir` + + * libraries specified with :option:`-llib` + + * library search directories specified with :option:`-Ldir` + + * compile handled by :program:`cc` (or similar) executable with + :option:`-c` option: compiles :file:`.c` to :file:`.o` + + * link static library handled by :program:`ar` command (possibly with + :program:`ranlib`) + + * link shared library handled by :program:`cc` :option:`-shared` + + +.. [#] On Windows, extension modules typically need to be compiled with the same + compiler that was used to compile CPython (for example Microsoft Visual + Studio .NET 2003 for CPython 2.4 and 2.5). The AMD64 and Itanium + binaries are created using the Platform SDK. + + Under the hood, there are actually two different subclasses of + :class:`~.ccompiler.CCompiler` defined: one is compatible with MSVC 2005 + and 2008, the other works with older versions. This should not be a + concern for regular use of the functions in this module. + + Packaging will normally choose the right compiler, linker etc. on its + own. To override this choice, the environment variables + *DISTUTILS_USE_SDK* and *MSSdk* must be both set. *MSSdk* indicates that + the current environment has been setup by the SDK's ``SetEnv.Cmd`` + script, or that the environment variables had been registered when the + SDK was installed; *DISTUTILS_USE_SDK* indicates that the user has made + an explicit choice to override the compiler selection done by Packaging. + + .. TODO document the envvars in Doc/using and the man page + + +:mod:`packaging.compiler.ccompiler` --- CCompiler base class +============================================================ + +.. module:: packaging.compiler.ccompiler + :synopsis: Abstract CCompiler class. + + +This module provides the abstract base class for the :class:`CCompiler` +classes. A :class:`CCompiler` instance can be used for all the compile and +link steps needed to build a single project. Methods are provided to set +options for the compiler --- macro definitions, include directories, link path, +libraries and the like. + +.. class:: CCompiler([verbose=0, dry_run=0, force=0]) + + The abstract base class :class:`CCompiler` defines the interface that must be + implemented by real compiler classes. The class also has some utility + methods used by several compiler classes. + + The basic idea behind a compiler abstraction class is that each instance can + be used for all the compile/link steps in building a single project. Thus, + attributes common to all of those compile and link steps --- include + directories, macros to define, libraries to link against, etc. --- are + attributes of the compiler instance. To allow for variability in how + individual files are treated, most of those attributes may be varied on a + per-compilation or per-link basis. + + The constructor for each subclass creates an instance of the Compiler object. + Flags are *verbose* (show verbose output), *dry_run* (don't actually execute + the steps) and *force* (rebuild everything, regardless of dependencies). All + of these flags default to ``0`` (off). Note that you probably don't want to + instantiate :class:`CCompiler` or one of its subclasses directly - use the + :func:`packaging.CCompiler.new_compiler` factory function instead. + + The following methods allow you to manually alter compiler options for the + instance of the Compiler class. + + + .. method:: CCompiler.add_include_dir(dir) + + Add *dir* to the list of directories that will be searched for header + files. The compiler is instructed to search directories in the order in + which they are supplied by successive calls to :meth:`add_include_dir`. + + + .. method:: CCompiler.set_include_dirs(dirs) + + Set the list of directories that will be searched to *dirs* (a list of + strings). Overrides any preceding calls to :meth:`add_include_dir`; + subsequent calls to :meth:`add_include_dir` add to the list passed to + :meth:`set_include_dirs`. This does not affect any list of standard + include directories that the compiler may search by default. + + + .. method:: CCompiler.add_library(libname) + + Add *libname* to the list of libraries that will be included in all links + driven by this compiler object. Note that *libname* should *not* be the + name of a file containing a library, but the name of the library itself: + the actual filename will be inferred by the linker, the compiler, or the + compiler class (depending on the platform). + + The linker will be instructed to link against libraries in the order they + were supplied to :meth:`add_library` and/or :meth:`set_libraries`. It is + perfectly valid to duplicate library names; the linker will be instructed + to link against libraries as many times as they are mentioned. + + + .. method:: CCompiler.set_libraries(libnames) + + Set the list of libraries to be included in all links driven by this + compiler object to *libnames* (a list of strings). This does not affect + any standard system libraries that the linker may include by default. + + + .. method:: CCompiler.add_library_dir(dir) + + Add *dir* to the list of directories that will be searched for libraries + specified to :meth:`add_library` and :meth:`set_libraries`. The linker + will be instructed to search for libraries in the order they are supplied + to :meth:`add_library_dir` and/or :meth:`set_library_dirs`. + + + .. method:: CCompiler.set_library_dirs(dirs) + + Set the list of library search directories to *dirs* (a list of strings). + This does not affect any standard library search path that the linker may + search by default. + + + .. method:: CCompiler.add_runtime_library_dir(dir) + + Add *dir* to the list of directories that will be searched for shared + libraries at runtime. + + + .. method:: CCompiler.set_runtime_library_dirs(dirs) + + Set the list of directories to search for shared libraries at runtime to + *dirs* (a list of strings). This does not affect any standard search path + that the runtime linker may search by default. + + + .. method:: CCompiler.define_macro(name[, value=None]) + + Define a preprocessor macro for all compilations driven by this compiler + object. The optional parameter *value* should be a string; if it is not + supplied, then the macro will be defined without an explicit value and the + exact outcome depends on the compiler used (XXX true? does ANSI say + anything about this?) + + + .. method:: CCompiler.undefine_macro(name) + + Undefine a preprocessor macro for all compilations driven by this compiler + object. If the same macro is defined by :meth:`define_macro` and + undefined by :meth:`undefine_macro` the last call takes precedence + (including multiple redefinitions or undefinitions). If the macro is + redefined/undefined on a per-compilation basis (i.e. in the call to + :meth:`compile`), then that takes precedence. + + + .. method:: CCompiler.add_link_object(object) + + Add *object* to the list of object files (or analogues, such as explicitly + named library files or the output of "resource compilers") to be included + in every link driven by this compiler object. + + + .. method:: CCompiler.set_link_objects(objects) + + Set the list of object files (or analogues) to be included in every link + to *objects*. This does not affect any standard object files that the + linker may include by default (such as system libraries). + + The following methods implement methods for autodetection of compiler + options, providing some functionality similar to GNU :program:`autoconf`. + + + .. method:: CCompiler.detect_language(sources) + + Detect the language of a given file, or list of files. Uses the instance + attributes :attr:`language_map` (a dictionary), and :attr:`language_order` + (a list) to do the job. + + + .. method:: CCompiler.find_library_file(dirs, lib[, debug=0]) + + Search the specified list of directories for a static or shared library file + *lib* and return the full path to that file. If *debug* is true, look for a + debugging version (if that makes sense on the current platform). Return + ``None`` if *lib* wasn't found in any of the specified directories. + + + .. method:: CCompiler.has_function(funcname [, includes=None, include_dirs=None, libraries=None, library_dirs=None]) + + Return a boolean indicating whether *funcname* is supported on the current + platform. The optional arguments can be used to augment the compilation + environment by providing additional include files and paths and libraries and + paths. + + + .. method:: CCompiler.library_dir_option(dir) + + Return the compiler option to add *dir* to the list of directories searched for + libraries. + + + .. method:: CCompiler.library_option(lib) + + Return the compiler option to add *dir* to the list of libraries linked into the + shared library or executable. + + + .. method:: CCompiler.runtime_library_dir_option(dir) + + Return the compiler option to add *dir* to the list of directories searched for + runtime libraries. + + + .. method:: CCompiler.set_executables(**args) + + Define the executables (and options for them) that will be run to perform the + various stages of compilation. The exact set of executables that may be + specified here depends on the compiler class (via the 'executables' class + attribute), but most will have: + + +--------------+------------------------------------------+ + | attribute | description | + +==============+==========================================+ + | *compiler* | the C/C++ compiler | + +--------------+------------------------------------------+ + | *linker_so* | linker used to create shared objects and | + | | libraries | + +--------------+------------------------------------------+ + | *linker_exe* | linker used to create binary executables | + +--------------+------------------------------------------+ + | *archiver* | static library creator | + +--------------+------------------------------------------+ + + On platforms with a command line (Unix, DOS/Windows), each of these is a string + that will be split into executable name and (optional) list of arguments. + (Splitting the string is done similarly to how Unix shells operate: words are + delimited by spaces, but quotes and backslashes can override this. See + :func:`packaging.util.split_quoted`.) + + The following methods invoke stages in the build process. + + + .. method:: CCompiler.compile(sources[, output_dir=None, macros=None, include_dirs=None, debug=0, extra_preargs=None, extra_postargs=None, depends=None]) + + Compile one or more source files. Generates object files (e.g. transforms a + :file:`.c` file to a :file:`.o` file.) + + *sources* must be a list of filenames, most likely C/C++ files, but in reality + anything that can be handled by a particular compiler and compiler class (e.g. + an ``'msvc'`` compiler can handle resource files in *sources*). Return a list of + object filenames, one per source filename in *sources*. Depending on the + implementation, not all source files will necessarily be compiled, but all + corresponding object filenames will be returned. + + If *output_dir* is given, object files will be put under it, while retaining + their original path component. That is, :file:`foo/bar.c` normally compiles to + :file:`foo/bar.o` (for a Unix implementation); if *output_dir* is *build*, then + it would compile to :file:`build/foo/bar.o`. + + *macros*, if given, must be a list of macro definitions. A macro definition is + either a ``(name, value)`` 2-tuple or a ``(name,)`` 1-tuple. The former defines + a macro; if the value is ``None``, the macro is defined without an explicit + value. The 1-tuple case undefines a macro. Later + definitions/redefinitions/undefinitions take precedence. + + *include_dirs*, if given, must be a list of strings, the directories to add to + the default include file search path for this compilation only. + + *debug* is a boolean; if true, the compiler will be instructed to output debug + symbols in (or alongside) the object file(s). + + *extra_preargs* and *extra_postargs* are implementation-dependent. On platforms + that have the notion of a command line (e.g. Unix, DOS/Windows), they are most + likely lists of strings: extra command-line arguments to prepend/append to the + compiler command line. On other platforms, consult the implementation class + documentation. In any event, they are intended as an escape hatch for those + occasions when the abstract compiler framework doesn't cut the mustard. + + *depends*, if given, is a list of filenames that all targets depend on. If a + source file is older than any file in depends, then the source file will be + recompiled. This supports dependency tracking, but only at a coarse + granularity. + + Raises :exc:`CompileError` on failure. + + + .. method:: CCompiler.create_static_lib(objects, output_libname[, output_dir=None, debug=0, target_lang=None]) + + Link a bunch of stuff together to create a static library file. The "bunch of + stuff" consists of the list of object files supplied as *objects*, the extra + object files supplied to :meth:`add_link_object` and/or + :meth:`set_link_objects`, the libraries supplied to :meth:`add_library` and/or + :meth:`set_libraries`, and the libraries supplied as *libraries* (if any). + + *output_libname* should be a library name, not a filename; the filename will be + inferred from the library name. *output_dir* is the directory where the library + file will be put. XXX defaults to what? + + *debug* is a boolean; if true, debugging information will be included in the + library (note that on most platforms, it is the compile step where this matters: + the *debug* flag is included here just for consistency). + + *target_lang* is the target language for which the given objects are being + compiled. This allows specific linkage time treatment of certain languages. + + Raises :exc:`LibError` on failure. + + + .. method:: CCompiler.link(target_desc, objects, output_filename[, output_dir=None, libraries=None, library_dirs=None, runtime_library_dirs=None, export_symbols=None, debug=0, extra_preargs=None, extra_postargs=None, build_temp=None, target_lang=None]) + + Link a bunch of stuff together to create an executable or shared library file. + + The "bunch of stuff" consists of the list of object files supplied as *objects*. + *output_filename* should be a filename. If *output_dir* is supplied, + *output_filename* is relative to it (i.e. *output_filename* can provide + directory components if needed). + + *libraries* is a list of libraries to link against. These are library names, + not filenames, since they're translated into filenames in a platform-specific + way (e.g. *foo* becomes :file:`libfoo.a` on Unix and :file:`foo.lib` on + DOS/Windows). However, they can include a directory component, which means the + linker will look in that specific directory rather than searching all the normal + locations. + + *library_dirs*, if supplied, should be a list of directories to search for + libraries that were specified as bare library names (i.e. no directory + component). These are on top of the system default and those supplied to + :meth:`add_library_dir` and/or :meth:`set_library_dirs`. *runtime_library_dirs* + is a list of directories that will be embedded into the shared library and used + to search for other shared libraries that \*it\* depends on at run-time. (This + may only be relevant on Unix.) + + *export_symbols* is a list of symbols that the shared library will export. + (This appears to be relevant only on Windows.) + + *debug* is as for :meth:`compile` and :meth:`create_static_lib`, with the + slight distinction that it actually matters on most platforms (as opposed to + :meth:`create_static_lib`, which includes a *debug* flag mostly for form's + sake). + + *extra_preargs* and *extra_postargs* are as for :meth:`compile` (except of + course that they supply command-line arguments for the particular linker being + used). + + *target_lang* is the target language for which the given objects are being + compiled. This allows specific linkage time treatment of certain languages. + + Raises :exc:`LinkError` on failure. + + + .. method:: CCompiler.link_executable(objects, output_progname[, output_dir=None, libraries=None, library_dirs=None, runtime_library_dirs=None, debug=0, extra_preargs=None, extra_postargs=None, target_lang=None]) + + Link an executable. *output_progname* is the name of the file executable, while + *objects* are a list of object filenames to link in. Other arguments are as for + the :meth:`link` method. + + + .. method:: CCompiler.link_shared_lib(objects, output_libname[, output_dir=None, libraries=None, library_dirs=None, runtime_library_dirs=None, export_symbols=None, debug=0, extra_preargs=None, extra_postargs=None, build_temp=None, target_lang=None]) + + Link a shared library. *output_libname* is the name of the output library, + while *objects* is a list of object filenames to link in. Other arguments are + as for the :meth:`link` method. + + + .. method:: CCompiler.link_shared_object(objects, output_filename[, output_dir=None, libraries=None, library_dirs=None, runtime_library_dirs=None, export_symbols=None, debug=0, extra_preargs=None, extra_postargs=None, build_temp=None, target_lang=None]) + + Link a shared object. *output_filename* is the name of the shared object that + will be created, while *objects* is a list of object filenames to link in. + Other arguments are as for the :meth:`link` method. + + + .. method:: CCompiler.preprocess(source[, output_file=None, macros=None, include_dirs=None, extra_preargs=None, extra_postargs=None]) + + Preprocess a single C/C++ source file, named in *source*. Output will be written + to file named *output_file*, or *stdout* if *output_file* not supplied. + *macros* is a list of macro definitions as for :meth:`compile`, which will + augment the macros set with :meth:`define_macro` and :meth:`undefine_macro`. + *include_dirs* is a list of directory names that will be added to the default + list, in the same way as :meth:`add_include_dir`. + + Raises :exc:`PreprocessError` on failure. + + The following utility methods are defined by the :class:`CCompiler` class, for + use by the various concrete subclasses. + + + .. method:: CCompiler.executable_filename(basename[, strip_dir=0, output_dir='']) + + Returns the filename of the executable for the given *basename*. Typically for + non-Windows platforms this is the same as the basename, while Windows will get + a :file:`.exe` added. + + + .. method:: CCompiler.library_filename(libname[, lib_type='static', strip_dir=0, output_dir='']) + + Returns the filename for the given library name on the current platform. On Unix + a library with *lib_type* of ``'static'`` will typically be of the form + :file:`liblibname.a`, while a *lib_type* of ``'dynamic'`` will be of the form + :file:`liblibname.so`. + + + .. method:: CCompiler.object_filenames(source_filenames[, strip_dir=0, output_dir='']) + + Returns the name of the object files for the given source files. + *source_filenames* should be a list of filenames. + + + .. method:: CCompiler.shared_object_filename(basename[, strip_dir=0, output_dir='']) + + Returns the name of a shared object file for the given file name *basename*. + + + .. method:: CCompiler.execute(func, args[, msg=None, level=1]) + + Invokes :func:`packaging.util.execute` This method invokes a Python function + *func* with the given arguments *args*, after logging and taking into account + the *dry_run* flag. XXX see also. + + + .. method:: CCompiler.spawn(cmd) + + Invokes :func:`packaging.util.spawn`. This invokes an external process to run + the given command. XXX see also. + + + .. method:: CCompiler.mkpath(name[, mode=511]) + + Invokes :func:`packaging.dir_util.mkpath`. This creates a directory and any + missing ancestor directories. XXX see also. + + + .. method:: CCompiler.move_file(src, dst) + + Invokes :meth:`packaging.file_util.move_file`. Renames *src* to *dst*. XXX see + also. + + +:mod:`packaging.compiler.extension` --- The Extension class +=========================================================== + +.. module:: packaging.compiler.extension + :synopsis: Class used to represent C/C++ extension modules. + + +This module provides the :class:`Extension` class, used to represent C/C++ +extension modules. + +.. class:: Extension + + The Extension class describes a single C or C++ extension module. It accepts + the following keyword arguments in its constructor: + + +------------------------+--------------------------------+---------------------------+ + | argument name | value | type | + +========================+================================+===========================+ + | *name* | the full name of the | string | + | | extension, including any | | + | | packages --- i.e. *not* a | | + | | filename or pathname, but | | + | | Python dotted name | | + +------------------------+--------------------------------+---------------------------+ + | *sources* | list of source filenames, | list of strings | + | | relative to the distribution | | + | | root (where the setup script | | + | | lives), in Unix form (slash- | | + | | separated) for portability. | | + | | Source files may be C, C++, | | + | | SWIG (.i), platform-specific | | + | | resource files, or whatever | | + | | else is recognized by the | | + | | :command:`build_ext` command | | + | | as source for a Python | | + | | extension. | | + +------------------------+--------------------------------+---------------------------+ + | *include_dirs* | list of directories to search | list of strings | + | | for C/C++ header files (in | | + | | Unix form for portability) | | + +------------------------+--------------------------------+---------------------------+ + | *define_macros* | list of macros to define; each | list of tuples | + | | macro is defined using a | | + | | 2-tuple ``(name, value)``, | | + | | where *value* is | | + | | either the string to define it | | + | | to or ``None`` to define it | | + | | without a particular value | | + | | (equivalent of ``#define FOO`` | | + | | in source or :option:`-DFOO` | | + | | on Unix C compiler command | | + | | line) | | + +------------------------+--------------------------------+---------------------------+ + | *undef_macros* | list of macros to undefine | list of strings | + | | explicitly | | + +------------------------+--------------------------------+---------------------------+ + | *library_dirs* | list of directories to search | list of strings | + | | for C/C++ libraries at link | | + | | time | | + +------------------------+--------------------------------+---------------------------+ + | *libraries* | list of library names (not | list of strings | + | | filenames or paths) to link | | + | | against | | + +------------------------+--------------------------------+---------------------------+ + | *runtime_library_dirs* | list of directories to search | list of strings | + | | for C/C++ libraries at run | | + | | time (for shared extensions, | | + | | this is when the extension is | | + | | loaded) | | + +------------------------+--------------------------------+---------------------------+ + | *extra_objects* | list of extra files to link | list of strings | + | | with (e.g. object files not | | + | | implied by 'sources', static | | + | | library that must be | | + | | explicitly specified, binary | | + | | resource files, etc.) | | + +------------------------+--------------------------------+---------------------------+ + | *extra_compile_args* | any extra platform- and | list of strings | + | | compiler-specific information | | + | | to use when compiling the | | + | | source files in 'sources'. For | | + | | platforms and compilers where | | + | | a command line makes sense, | | + | | this is typically a list of | | + | | command-line arguments, but | | + | | for other platforms it could | | + | | be anything. | | + +------------------------+--------------------------------+---------------------------+ + | *extra_link_args* | any extra platform- and | list of strings | + | | compiler-specific information | | + | | to use when linking object | | + | | files together to create the | | + | | extension (or to create a new | | + | | static Python interpreter). | | + | | Similar interpretation as for | | + | | 'extra_compile_args'. | | + +------------------------+--------------------------------+---------------------------+ + | *export_symbols* | list of symbols to be exported | list of strings | + | | from a shared extension. Not | | + | | used on all platforms, and not | | + | | generally necessary for Python | | + | | extensions, which typically | | + | | export exactly one symbol: | | + | | ``init`` + extension_name. | | + +------------------------+--------------------------------+---------------------------+ + | *depends* | list of files that the | list of strings | + | | extension depends on | | + +------------------------+--------------------------------+---------------------------+ + | *language* | extension language (i.e. | string | + | | ``'c'``, ``'c++'``, | | + | | ``'objc'``). Will be detected | | + | | from the source extensions if | | + | | not provided. | | + +------------------------+--------------------------------+---------------------------+ + | *optional* | specifies that a build failure | boolean | + | | in the extension should not | | + | | abort the build process, but | | + | | simply skip the extension. | | + +------------------------+--------------------------------+---------------------------+ |