# 11.2 `distutils.ccompiler` -- CCompiler base class

This module provides the abstract base class for the `CCompiler` classes. A `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.

This module provides the following functions.

`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).

`gen_preprocess_options`( | macros, include_dirs)

  Generate C pre-processor options (-D, -U, -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 (-U) macro name, and `(name, value)` means define (-D) macro name to value. include_dirs is just a list of directory names to be added to the header file search path (-I). Returns a list of command-line options suitable for either Unix compilers or Visual C++.

`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` in case the parameters are not given.

`new_compiler`( | plat=`None`, compiler=`None`, verbose=`0`, dry_run=`0`, force=`0`)

  Factory function to generate an instance of some CCompiler subclass for the supplied platform/compiler combination. plat defaults to `os.name` (eg. `'posix'`, `'nt'`), and compiler defaults to the default compiler for that platform. Currently only `'posix'` and `'nt'` are supported, and the default compilers are ``traditional Unix interface'' (`UnixCCompiler` class) and Visual C++(`MSVCCompiler` class). Note that it's perfectly possible to ask for a Unix compiler object under Windows, and a Microsoft compiler object under Unix--if you supply a value for compiler, plat is ignored.

`show_compilers`( | )

  Print list of available compilers (used by the --help-compiler options to `build`, `build_ext`, `build_clib`).

class `CCompiler`( | [verbose=`0`, dry_run=`0`, force=`0`])

  The abstract base 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 `CCompiler` or one of its subclasses directly - use the `distutils.CCompiler.new_compiler()` factory function instead.

  The following methods allow you to manually alter compiler options for the instance of the Compiler class.

  `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 `add_include_dir()`.

  `set_include_dirs`( | dirs)

    Set the list of directories that will be searched to dirs (a list of strings). Overrides any preceding calls to `add_include_dir()`; subsequent calls to `add_include_dir()` add to the list passed to `set_include_dirs()`. This does not affect any list of standard include directories that the compiler may search by default.

  `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 `add_library()` and/or `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.

  `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.

  `add_library_dir`( | dir)

    Add dir to the list of directories that will be searched for libraries specified to `add_library()` and `set_libraries()`. The linker will be instructed to search for libraries in the order they are supplied to `add_library_dir()` and/or `set_library_dirs()`.

  `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.

  `add_runtime_library_dir`( | dir)

    Add dir to the list of directories that will be searched for shared libraries at runtime.

  `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.

  `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?)

  `undefine_macro`( | name)

    Undefine a preprocessor macro for all compilations driven by this compiler object. If the same macro is defined by `define_macro()` and undefined by `undefine_macro()` the last call takes precedence (including multiple redefinitions or undefinitions). If the macro is redefined/undefined on a per-compilation basis (ie. in the call to `compile()`), then that takes precedence.

  `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.

  `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 autoconf.

  `detect_language`( | sources)

    Detect the language of a given file, or list of files. Uses the instance attributes `language_map` (a dictionary), and `language_order` (a list) to do the job.

  `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.

  `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.

  `library_dir_option`( | dir)

    Return the compiler option to add dir to the list of directories searched for libraries.

  `library_option`( | lib)

    Return the compiler option to add dir to the list of libraries linked into the shared library or executable.

  `runtime_library_dir_option`( | dir)

    Return the compiler option to add dir to the list of directories searched for runtime libraries.

  `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 `distutils.util.split_quoted()`.)

  The following methods invoke stages in the build process.

  `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 .c file to a .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 (eg. `MSVCCompiler` 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, foo/bar.c normally compiles to foo/bar.o (for a Unix implementation); if output_dir is build, then it would compile to 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 `CompileError` on failure.

  `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 `add_link_object()` and/or `set_link_objects()`, the libraries supplied to `add_library()` and/or `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 `LibError` on failure.

  `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 (eg. foo becomes libfoo.a on Unix and 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 (ie. no directory component). These are on top of the system default and those supplied to `add_library_dir()` and/or `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 `compile()` and `create_static_lib()`, with the slight distinction that it actually matters on most platforms (as opposed to `create_static_lib()`, which includes a debug flag mostly for form's sake).

    extra_preargs and extra_postargs are as for `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 `LinkError` on failure.

  `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 `link` method.

  `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 `link` method.

  `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 `link` method.

  `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 `compile()`, which will augment the macros set with `define_macro()` and `undefine_macro()`. include_dirs is a list of directory names that will be added to the default list, in the same way as `add_include_dir()`.

    Raises `PreprocessError` on failure.

  The following utility methods are defined by the `CCompiler` class, for use by the various concrete subclasses.

  `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 .exe added.

  `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 liblibname.a, while a lib_type of `'dynamic'` will be of the form liblibname.so.

  `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.

  `shared_object_filename`( | basename[, strip_dir=`0`, output_dir=`''`])

    Returns the name of a shared object file for the given file name basename.

  `execute`( | func, args[, msg=`None`, level=`1`])

    Invokes `distutils.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.

  `spawn`( | cmd)

    Invokes `distutils.util.spawn()`. This invokes an external process to run the given command. XXX see also.

  `mkpath`( | name[, mode=`511`])

    Invokes `distutils.dir_util.mkpath()`. This creates a directory and any missing ancestor directories. XXX see also.

  `move_file`( | src, dst)

    Invokes `distutils.file_util.move_file()`. Renames src to dst. XXX see also.

  `announce`( | msg[, level=`1`])

    Write a message using `distutils.log.debug()`. XXX see also.

  `warn`( | msg)

    Write a warning message msg to standard error.

  `debug_print`( | msg)

    If the debug flag is set on this `CCompiler` instance, print msg to standard output, otherwise do nothing.