system-definition := ( defsystem system-designator system-option* ) system-option := :defsystem-depends-on system-list | :weakly-depends-on system-list | :class class-name # see System class names | :build-operation operation-name | system-option | module-option | option # These are only available since ASDF 3 (actually its alpha release 2.27) system-option := :homepage string | :bug-tracker string | :mailto string | :long-name string | :source-control source-control | :version version-specifier | :entry-point object # see Entry point source-control := (keyword string) module-option := :components component-list | :serial [ t | nil ] option := | :pathname pathname-specifier | :default-component-class class-name | :perform method-form | :explain method-form | :output-files method-form | :operation-done-p method-form | :if-feature feature-expression | :depends-on ( dependency-def* ) | :in-order-to ( dependency+ ) system-list := ( simple-component-name* ) component-list := ( component-def* ) component-def := ( component-type simple-component-name option* ) component-type := :module | :file | :static-file | other-component-type other-component-type := symbol-by-name # see Component types # This is used in :depends-on, as opposed to ``dependency,'' # which is used in :in-order-to dependency-def := simple-component-name | ( :feature feature-expression dependency-def ) # see Feature dependencies | ( :version simple-component-name version-specifier ) | ( :require module-name ) # ``dependency'' is used in :in-order-to, as opposed to # ``dependency-def'' dependency := (dependent-op requirement+) requirement := (required-op required-component+) dependent-op := operation-name required-op := operation-name simple-component-name := string | symbol pathname-specifier := pathname | string | symbol version-specifier := string | (:read-file-form <pathname-specifier> <form-specifier>?) | (:read-file-line <pathname-specifier> <line-specifier>?) line-specifier := :at integer # base zero form-specifier := :at [ integer | ( integer+ )] method-form := (operation-name qual lambda-list &rest body) qual := method-qualifier? method-qualifier = :before | :after | :around feature-expression := keyword | (:and feature-expression*) | (:or feature-expression*) | (:not feature-expression)
Component names (
may be either strings or symbols.
Component type names, even if expressed as keywords, will be looked up
by name in the current package and in the asdf package, if not found in
the current package. So a component type
the current package
my-system-asd can be specified as
system and its subclasses are not
allowed as component types for such children components.
A system class name will be looked up
in the same way as a Component type (see above),
except that only
system and its subclasses are allowed.
Typically, one will not need to specify a system
class name, unless using a non-standard system class defined in some
ASDF extension, typically loaded through
see below. For such class names in the ASDF package, we recommend that
:class option be specified using a keyword symbol, such as
This practice will ensure that package name conflicts are avoided.
Otherwise, the symbol
MY-NEW-SYSTEM-SUBCLASS will be read into
the current package before it has been exported from the ASDF
extension loaded by
:defsystem-depends-on, causing a name
conflict in the current package.
:defsystem-depends-on option to
defsystem allows the
programmer to specify another ASDF-defined system or set of systems that
must be loaded before the system definition is processed.
Typically this is used to load an ASDF extension that is used in the
:build-operation option to
defsystem allows the
programmer to specify an operation that will be applied, in place of
make (see make)
is run on the system. The option
value should be the name of an operation. E.g.,
This feature is experimental and largely untested. Use at your own risk.
We do NOT recommend you use this feature. If you are tempted to write a system foo that weakly-depends-on a system bar, we recommend that you should instead write system foo in a parametric way, and offer some special variable and/or some hook to specialize its behaviour; then you should write a system foo+bar that does the hooking of things together.
:weakly-depends-on option to
allows the programmer to specify another ASDF-defined system or set of systems
that ASDF should try to load,
but need not load in order to be successful.
Typically this is used if there are a number of systems
that, if present, could provide additional functionality,
but which are not necessary for basic function.
Currently, although it is specified to be an option only to
this option is accepted at any component, but it probably
only makes sense at the
Programmers are cautioned not
to use this component option except at the
defsystem level, as
this anomalous behaviour may be removed without warning.
A pathname specifier (
may be a pathname, a string or a symbol.
When no pathname specifier is given for a component,
which is the usual case, the component name itself is used.
If a string is given, which is the usual case,
the string will be interpreted as a Unix-style pathname
/ characters will be interpreted as directory separators.
Usually, Unix-style relative pathnames are used
(i.e. not starting with
/, as opposed to absolute pathnames);
they are relative to the path of the parent component.
Finally, depending on the
the pathname may be interpreted as either a file or a directory,
and if it’s a file,
a file type may be added corresponding to the
or else it will be extracted from the string itself (if applicable).
For instance, the
wants a directory pathname, and so a string
will be interpreted as the pathname #p"foo/bar/".
On the other hand, the
wants a file of type
lisp, and so a string
will be interpreted as the pathname #p"foo/bar.lisp",
and a string
will be interpreted as the pathname #p"foo/bar.quux.lisp".
wants a file without specifying a type, and so a string
will be interpreted as the pathname #p"foo/bar",
and a string
will be interpreted as the pathname #p"foo/bar.quux".
ASDF interprets the string
as the pathname directory component word
which when merged, goes back one level in the directory hierarchy.
If a symbol is given, it will be translated into a string,
and downcased in the process.
The downcasing of symbols is unconventional,
but was selected after some consideration.
Observations suggest that the type of systems we want to support
either have lowercase as customary case (Unix, Mac, windows)
or silently convert lowercase to uppercase (lpns),
so this makes more sense than attempting to use
as argument to
which is reported not to work on some implementations.
Pathname objects may be given to override the path for a component.
Such objects are typically specified using reader macros such as
Note however, that
a shorthand for
and that the behaviour of
parse-namestring is completely non-portable,
unless you are using Common Lisp
which themselves involve other non-portable behaviour
(see Using logical pathnames).
Pathnames made with
can usually be done more easily with the string syntax above.
The only case that you really need a pathname object is to override
the component-type default file type for a given component.
Therefore, pathname objects should only rarely be used.
Unhappily, ASDF 1 used not to properly support
parsing component names as strings specifying paths with directories,
and the cumbersome
#.(make-pathname ...) syntax had to be used.
An alternative to
#. read-time evaluation is to use
(eval `(defsystem ... ,pathname ...)).
Note that when specifying pathname objects, ASDF does not do any special interpretation of the pathname influenced by the component type, unlike the procedure for pathname-specifying strings. On the one hand, you have to be careful to provide a pathname that correctly fulfills whatever constraints are required from that component type (e.g. naming a directory or a file with appropriate type); on the other hand, you can circumvent the file type that would otherwise be forced upon you if you were specifying a string.
Version specifiers are strings to be parsed as period-separated lists of integers.
I.e., in the example,
"0.2.1" is to be interpreted,
roughly speaking, as
(0 2 1).
In particular, version
"0.2.1" is interpreted the same as
though the latter is not canonical and may lead to a warning being issued.
"1.4" are both strictly
quite unlike what would have happened
had the version strings been interpreted as decimal fractions.
Instead of a string representing the version,
:version argument can be an expression that is resolved to
such a string using the following trivial domain-specific language:
in addition to being a literal string, it can be an expression of the form
(:read-file-form <pathname-or-string> [:at <access-at-specifier>]),
(:read-file-line <pathname-or-string> [:at <access-at-specifier>]).
As the name suggests, the former will be resolved by reading a form in the specified pathname
(read as a subpathname of the current system if relative or a
unix-namestring), and the latter by reading a line.
You may use a
by default the specifier is
0, meaning the first form/line is
subforms can also be specified, with e.g.
(1 2 2) specifying
“the third subform (index 2) of the third subform (index 2) of the second form (index 1)”
in the file (mind the off-by-one error in the English language).
System definers are encouraged to use version identifiers of the form x.y.z for major version, minor version and patch level, where significant API incompatibilities are signaled by an increased major number.
See Common attributes of components.
Use the implementation’s own
require to load the module-name.
It is good taste to use
(:feature :implementation-name (:require module-name))
#+implementation-name (:require module-name)
to only depend on the specified module on the specific implementation that provides it.
See Feature dependencies.
A feature dependency is of the form
(:feature feature-expression dependency)
If the feature-expression is satisfied by the running lisp at the
time the system definition is parsed, then the dependency will be
added to the system’s dependencies. If the feature-expression is
not satisfied, then the feature dependency form is ignored.
Note that this means that
:feature cannot be used to
enforce a feature dependency for the system in question. I.e., it
cannot be used to require that a feature hold in order for the system
definition to be loaded. E.g., one cannot use
to require that a system only be used on SBCL.
Feature dependencies are not to be confused with the obsolete
feature requirement (see feature requirement), or
We do not generally recommend the use of logical pathnames, especially not so to newcomers to Common Lisp. However, we do support the use of logical pathnames by old timers, when such is their preference.
To use logical pathnames,
you will have to provide a pathname object as a
to components that use it, using such syntax as
You only have to specify such logical pathname for your system or some top-level component. Sub-components’ relative pathnames, specified using the string syntax for names, will be properly merged with the pathnames of their parents. The specification of a logical pathname host however is not otherwise directly supported in the ASDF syntax for pathname specifiers as strings.
asdf-output-translation layer will
avoid trying to resolve and translate logical pathnames.
The advantage of this is that
you can define yourself what translations you want to use
with the logical pathname facility.
The disadvantage is that if you do not define such translations,
any system that uses logical pathnames will behave differently under
asdf-output-translations than other systems you use.
If you wish to use logical pathnames you will have to configure the translations yourself before they may be used. ASDF currently provides no specific support for defining logical pathname translations.
Note that the reasons we do not recommend logical pathnames are that (1) there is no portable way to set up logical pathnames before they are used, (2) logical pathnames are limited to only portably use a single character case, digits and hyphens. While you can solve the first issue on your own, describing how to do it on each of fifteen implementations supported by ASDF is more than we can document. As for the second issue, mind that the limitation is notably enforced on SBCL, and that you therefore can’t portably violate the limitations but must instead define some encoding of your own and add individual mappings to name physical pathnames that do not fit the restrictions. This can notably be a problem when your Lisp files are part of a larger project in which it is common to name files or directories in a way that includes the version numbers of supported protocols, or in which files are shared with software written in different programming languages where conventions include the use of underscores, dots or CamelCase in pathnames.
:serial t option is specified for a module,
ASDF will add dependencies for each child component,
on all the children textually preceding it.
This is done as if by
:serial t :components ((:file "a") (:file "b") (:file "c"))
is equivalent to
:components ((:file "a") (:file "b" :depends-on ("a")) (:file "c" :depends-on ("a" "b")))
:pathname option is optional in all cases for systems
defsystem, and generally is unnecessary. In the
simple case, source files will be found in the same directory as the
system or, in the case of modules, in a subdirectory with the same name
as the module.
More specifically, ASDF follows a hairy set of rules that are designed so that
find-systemwill load a system from disk and have its pathname default to the right place.
*default-pathname-defaults*(which could be somewhere else altogether) if the user loads up the .asd file into his editor and interactively re-evaluates that form.
If a system is being loaded for the first time, its top-level pathname will be set to:
*load-truename*, if it is bound.
If a system is being redefined, the top-level pathname will be
*load-truename*(so that an updated source location is reflected in the system definition)
*load-truename*is currently unbound (so that a developer can evaluate a
defsystemform from within an editor without clobbering its source location)
This option allows you to specify a feature expression to be evaluated
as if by
#+ to conditionally include a component in your build.
If the expression is false, the component is dropped
as well as any dependency pointing to it.
As compared to using
#+ which is expanded at read-time,
this allows you to have an object in your component hierarchy
that can be used for manipulations beside building your project, and
that is accessible to outside code that wishes to reason about system
Programmers should be careful to consider when the
:if-feature is evaluated. Recall that ASDF first computes a
build plan, and then executes that plan. ASDF will check to see whether
or not a feature is present at planning time, not during the
build. It follows that one cannot use
:if-feature to check
features that are set during the course of the build. It can only be
used to check the state of features before any build operations have
This option was added in ASDF 3. For more information, See Required features.
:entry-point option allows a developer to specify the entry point of an executable program created by
program-op is invoked, the form passed to this option is converted to a function by
uiop:ensure-function and bound to
uiop:*image-entry-point*. Typically one will specify a string, e.g.
"foo:main", so that the executable starts with the
foo:main function. Note that using the symbol
foo:main instead might not work because the
foo package doesn’t necessarily exist when ASDF reads the
defsystem form. For more information on
program-op, see Predefined operations of ASDF.
This requirement was removed in ASDF 3.1. Please do not use it. In
:if-feature (see if-feature option) will provide
an adequate substitute.
feature requirement used to ensure that a chain of component
dependencies would fail when a key feature was absent.
Used in conjunction with
a roundabout way to express conditional compilation.