.TH "Builtin_attributes" 3 2024-05-31 OCamldoc "OCaml library"
.SH NAME
Builtin_attributes \- Support for the builtin attributes:
.SH Module
Module   Builtin_attributes
.SH Documentation
.sp
Module
.BI "Builtin_attributes"
 : 
.B sig end

.sp
Support for the builtin attributes:
.sp
.sp
\-ocaml\&.alert
.sp
\-ocaml\&.boxed
.sp
\-ocaml\&.deprecated
.sp
\-ocaml\&.deprecated_mutable
.sp
\-ocaml\&.explicit_arity
.sp
\-ocaml\&.immediate
.sp
\-ocaml\&.immediate64
.sp
\-ocaml\&.inline
.sp
\-ocaml\&.inlined
.sp
\-ocaml\&.noalloc
.sp
\-ocaml\&.poll
.sp
\-ocaml\&.ppwarning
.sp
\-ocaml\&.specialise
.sp
\-ocaml\&.specialised
.sp
\-ocaml\&.tailcall
.sp
\-ocaml\&.tail_mod_cons
.sp
\-ocaml\&.unboxed
.sp
\-ocaml\&.untagged
.sp
\-ocaml\&.unrolled
.sp
\-ocaml\&.warnerror
.sp
\-ocaml\&.warning
.sp
\-ocaml\&.warn_on_literal_pattern

Warning: this module is unstable and part of
.ft B
Compiler_libs
.ft R
\&.

.sp

.sp
.sp

.PP
.SS Attribute tracking for warning 53

.PP
.I type current_phase 
=
 | Parser
 | Invariant_check
 
.sp

.ft B
register_attr
.ft R
must be called on the locations of all attributes that
should be tracked for the purpose of misplaced attribute warnings\&.  In
particular, it should be called on all attributes that are present in the
source program except those that are contained in the payload of another
attribute (because these may be left behind by a ppx and intentionally
ignored by the compiler)\&.
.sp
The 
.ft B
current_phase
.ft R
argument indicates when this function is being called
.sp
\-either when an attribute is created in the parser or when we see an
attribute while running the check in the 
.ft B
Ast_invariants
.ft R
module\&.  This is
used to ensure that we track only attributes from the final version of the
parse tree: we skip adding attributes seen at parse time if we can see that
a ppx will be run later, because the 
.ft B
Ast_invariants
.ft R
check is always run on
the result of a ppx\&.

Note that the 
.ft B
Ast_invariants
.ft R
check is also run on parse trees created from
marshalled ast files if no ppx is being used, ensuring we don\&'t miss
attributes in that case\&.

.sp

.I val register_attr 
: 
.B current_phase -> string Location.loc -> unit
.sp

.sp

.I val mark_payload_attrs_used 
: 
.B Parsetree.payload -> unit
.sp
Marks the attributes hiding in the payload of another attribute used, for
the purposes of misplaced attribute warnings (see comment on
.ft B
current_phase
.ft R
above)\&.  In the parser, it\&'s simplest to add these to
the table and remove them later, rather than threading through state
tracking whether we\&'re in an attribute payload\&.

.sp

.I val warn_unused 
: 
.B unit -> unit
.sp
Issue misplaced attribute warnings for all attributes created with
.ft B
mk_internal
.ft R
but not yet marked used\&.

.sp

.PP
.SS Warning 53 helpers for environment attributes
.sp
Some attributes, like deprecation markers, do not affect the compilation of
the definition on which they appear, but rather result in warnings on future
uses of that definition\&.  This is implemented by moving the raw attributes
into the environment, where they will be noticed on future accesses\&.
.sp
To make misplaced attribute warnings work appropriately for these
attributes, we mark them "used" when they are moved into the environment\&.
This is done with the helper functions in this section\&.
.PP

.I val mark_alert_used 
: 
.B Parsetree.attribute -> unit
.sp
Marks the attribute used for the purposes of misplaced attribute warnings if
it is an alert\&.  Call this when moving things allowed to have alert
attributes into the environment\&.

.sp

.I val mark_alerts_used 
: 
.B Parsetree.attributes -> unit
.sp
The same as 
.ft B
List\&.iter mark_alert_used
.ft R
\&.

.sp

.I val mark_warn_on_literal_pattern_used 
: 
.B Parsetree.attributes -> unit
.sp
Marks "warn_on_literal_pattern" attributes used for the purposes of
misplaced attribute warnings\&.  Call this when moving constructors into the
environment\&.

.sp

.I val mark_deprecated_mutable_used 
: 
.B Parsetree.attributes -> unit
.sp
Marks "deprecated_mutable" attributes used for the purposes of misplaced
attribute warnings\&.  Call this when moving labels of mutable fields into the
environment\&.

.sp

.PP
.SS Helpers for alert and warning attributes

.PP

.I val check_alerts 
: 
.B Location.t -> Parsetree.attributes -> string -> unit
.sp

.sp

.I val check_alerts_inclusion 
: 
.B def:Location.t ->
.B   use:Location.t ->
.B   Location.t -> Parsetree.attributes -> Parsetree.attributes -> string -> unit
.sp

.sp

.I val alerts_of_attrs 
: 
.B Parsetree.attributes -> Misc.alerts
.sp

.sp

.I val alerts_of_sig 
: 
.B Parsetree.signature -> Misc.alerts
.sp

.sp

.I val alerts_of_str 
: 
.B Parsetree.structure -> Misc.alerts
.sp

.sp

.I val check_deprecated_mutable 
: 
.B Location.t -> Parsetree.attributes -> string -> unit
.sp

.sp

.I val check_deprecated_mutable_inclusion 
: 
.B def:Location.t ->
.B   use:Location.t ->
.B   Location.t -> Parsetree.attributes -> Parsetree.attributes -> string -> unit
.sp

.sp

.I val error_of_extension 
: 
.B Parsetree.extension -> Location.error
.sp

.sp

.I val warning_attribute 
: 
.B ?ppwarning:bool -> Parsetree.attribute -> unit
.sp
Apply warning settings from the specified attribute\&.
"ocaml\&.warning"/"ocaml\&.warnerror" (and variants without the prefix) are
processed and marked used for warning 53\&.  Other attributes are ignored\&.
.sp
Also implement ocaml\&.ppwarning (unless ~ppwarning:false is
passed)\&.

.sp

.I val warning_scope 
: 
.B ?ppwarning:bool -> Parsetree.attributes -> (unit -> 'a) -> 'a
.sp
Execute a function in a new scope for warning settings\&.  This
means that the effect of any call to 
.ft B
warning_attribute
.ft R
during
the execution of this function will be discarded after
execution\&.
.sp
The function also takes a list of attributes which are processed
with 
.ft B
warning_attribute
.ft R
in the fresh scope before the function
is executed\&.

.sp

.PP
.SS Helpers for searching for particular attributes

.PP

.I val has_attribute 
: 
.B string -> Parsetree.attributes -> bool
.sp

.ft B
has_attribute name attrs
.ft R
is true if an attribute with name 
.ft B
name
.ft R
or
.ft B
"ocaml\&." ^ name
.ft R
is present in 
.ft B
attrs
.ft R
\&.  It marks that attribute used for
the purposes of misplaced attribute warnings\&.

.sp
.I type attr_action 
=
 | Mark_used_only
 | Return
 
.sp

.ft B
select_attributes actions attrs
.ft R
finds the elements of 
.ft B
attrs
.ft R
that appear
in 
.ft B
actions
.ft R
and either returns them or just marks them used, according to
the corresponding 
.ft B
attr_action
.ft R
\&.
.sp
Each element 
.ft B
(nm, action)
.ft R
of the 
.ft B
actions
.ft R
list is an attribute along with
an 
.ft B
attr_action
.ft R
specifying what to do with that attribute\&.  The action is
used to accommodate different compiler configurations\&.  If an attribute is
used only in some compiler configurations, it\&'s important that we still look
for it and mark it used when compiling with other configurations\&.
Otherwise, we would issue spurious misplaced attribute warnings\&.

.sp

.I val select_attributes 
: 
.B (string * attr_action) list ->
.B   Parsetree.attributes -> Parsetree.attributes
.sp

.sp

.I val attr_equals_builtin 
: 
.B Parsetree.attribute -> string -> bool
.sp

.ft B
attr_equals_builtin attr s
.ft R
is true if the name of the attribute is 
.ft B
s
.ft R
or
.ft B
"ocaml\&." ^ s
.ft R
\&.  This is useful for manually inspecting attribute names, but
note that doing so will not result in marking the attribute used for the
purpose of warning 53, so it is usually preferrable to use 
.ft B
has_attribute
.ft R
or 
.ft B
select_attributes
.ft R
\&.

.sp

.I val warn_on_literal_pattern 
: 
.B Parsetree.attributes -> bool
.sp

.sp

.I val explicit_arity 
: 
.B Parsetree.attributes -> bool
.sp

.sp

.I val immediate 
: 
.B Parsetree.attributes -> bool
.sp

.sp

.I val immediate64 
: 
.B Parsetree.attributes -> bool
.sp

.sp

.I val has_unboxed 
: 
.B Parsetree.attributes -> bool
.sp

.sp

.I val has_boxed 
: 
.B Parsetree.attributes -> bool
.sp

.sp