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:orphan:
.. _ABI:
.. highlight:: none
Mangling
--------
::
mangled-name ::= '$s' global // Swift stable mangling
mangled-name ::= '@__swiftmacro_' global // Swift mangling for filenames
mangled-name ::= '_T0' global // Swift 4.0
mangled-name ::= '$S' global // Swift 4.2
mangled-name ::= '$e' global // Embedded Swift (unstable)
All Swift-mangled names begin with a common prefix. Since Swift 4.0, the
compiler has used variations of the mangling described in this document, though
pre-stable versions may not exactly conform to this description. By using
distinct prefixes, tools can attempt to accommodate bugs and version variations
in pre-stable versions of Swift.
The basic mangling scheme is a list of 'operators' where the operators are
structured in a post-fix order. For example the mangling may start with an
identifier but only later in the mangling a type-like operator defines how this
identifier has to be interpreted::
4Test3FooC // The trailing 'C' says that 'Foo' is a class in module 'Test'
Operators are either identifiers or a sequence of one or more characters,
like ``C`` for class.
All operators share the same name-space. Important operators are a single
character, which means that no other operator may start with the same
character.
Some less important operators are longer and may also contain one or more
natural numbers. But it's always important that the demangler can identify the
end (the last character) of an operator. For example, it's not possible to
determine the last character if there are two operators ``M`` and ``Ma``:
``a`` could belong to ``M`` or it could be the first character of the next
operator.
The intention of the post-fix order is to optimize for common pre-fixes.
Regardless, if it's the mangling for a metatype or a function in a module, the
mangled name will start with the module name (after the ``_S``).
In the following, productions which are only _part_ of an operator, are
named with uppercase letters.
Symbolic references
~~~~~~~~~~~~~~~~~~~
The Swift compiler emits mangled names into binary images to encode
references to types for runtime instantiation and reflection. In a binary,
these mangled names may embed pointers to runtime data
structures in order to more efficiently represent locally-defined types.
We call these pointers **symbolic references**.
These references will be introduced by a control character in the range
`\x01` ... `\x1F`, which indicates the kind of symbolic reference, followed by
some number of arbitrary bytes *which may include null bytes*. Code that
processes mangled names out of Swift binaries needs to be aware of symbolic
references in order to properly terminate strings; a null terminator may be
part of a symbolic reference.
::
symbolic-reference ::= [\x01-\x17] .{4} // Relative symbolic reference
#if sizeof(void*) == 8
symbolic-reference ::= [\x18-\x1F] .{8} // Absolute symbolic reference for 64-bit pointers
#elif sizeof(void*) == 4
symbolic-reference ::= [\x18-\x1F] .{4} // Absolute symbolic reference for 32-bit pointers
#endif
Symbolic references are only valid in compiler-emitted metadata structures
and must only appear in read-only parts of a binary image. APIs and tools
that interpret Swift mangled names from potentially uncontrolled inputs must
refuse to interpret symbolic references.
The following symbolic reference kinds are currently implemented:
::
#if SWIFT_RUNTIME_VERSION < 5.1
{any-generic-type, protocol} ::= '\x01' .{4} // Reference points directly to context descriptor
{any-generic-type, protocol} ::= '\x02' .{4} // Reference points indirectly to context descriptor
#else
{any-generic-type, protocol, opaque-type-decl-name} ::= '\x01' .{4} // Reference points directly to context descriptor
{any-generic-type, protocol, opaque-type-decl-name} ::= '\x02' .{4} // Reference points indirectly to context descriptor
#endif
// The grammatical role of the symbolic reference is determined by the
// kind of context descriptor referenced
protocol-conformance-ref ::= '\x03' .{4} // Reference points directly to protocol conformance descriptor (NOT IMPLEMENTED)
protocol-conformance-ref ::= '\x04' .{4} // Reference points indirectly to protocol conformance descriptor (NOT IMPLEMENTED)
dependent-associated-conformance ::= '\x05' .{4} // Reference points directly to associated conformance descriptor (NOT IMPLEMENTED)
dependent-associated-conformance ::= '\x06' .{4} // Reference points indirectly to associated conformance descriptor (NOT IMPLEMENTED)
associated-conformance-access-function ::= '\x07' .{4} // Reference points directly to associated conformance access function relative to the protocol
associated-conformance-access-function ::= '\x08' .{4} // Reference points directly to associated conformance access function relative to the conforming type
// keypaths only in Swift 5.0, generalized in Swift 5.1
#if SWIFT_RUNTIME_VERSION >= 5.1
metadata-access-function ::= '\x09' .{4} // Reference points directly to metadata access function that can be invoked to produce referenced object
#endif
#if SWIFT_RUNTIME_VERISON >= 5.7
symbolic-extended-existential-type-shape ::= '\x0A' .{4} // Reference points directly to an ExtendedExistentialTypeShape
symbolic-extended-existential-type-shape ::= '\x0B' .{4} // Reference points directly to a NonUniqueExtendedExistentialTypeShape
#endif
#if SWIFT_RUNTIME_VERSION >= 5.TBD
objective-c-protocol-relative-reference ::= '\x0C' .{4} // Reference points directly to a objective-c protcol reference
#endif
Mangled names that contain relative symbolic references may include ``\xFF``
bytes for alignment padding purposes. These bytes do not affect what the mangled
name references and can be skipped over and ignored.
DISCUSSION: A relative symbolic reference encodes a symbol by adding the offset
integer value contained within the relative symbolic reference to the address in
memory of the first byte of the relative symbolic reference. The addition of
padding bytes is used to manipulate the location of that first byte so that the
address of is already aligned in the same manner as the symbol that is
ultimately referenced. Thus only an offset must be added to that address instead
of also needing to consider alignment differences.
Globals
~~~~~~~
::
global ::= type 'N' // type metadata (address point)
// -- type starts with [BCOSTV]
global ::= type 'Mf' // 'full' type metadata (start of object)
global ::= type 'MP' // type metadata pattern
global ::= type 'Ma' // type metadata access function
global ::= type 'ML' // type metadata lazy cache variable
global ::= nominal-type 'Mr' // generic type completion function
global ::= nominal-type 'Mi' // generic type instantiation function
global ::= nominal-type 'MI' // generic type instantiation cache
global ::= nominal-type 'Ml' // in-place type initialization cache
global ::= nominal-type 'Mm' // class metaclass
global ::= nominal-type 'Mn' // nominal type descriptor
#if SWIFT_RUNTIME_VERSION >= 5.1
global ::= opaque-type-decl-name 'MQ' // opaque type descriptor -- added in Swift 5.1
#endif
global ::= nominal-type 'Mu' // class method lookup function
global ::= nominal-type 'MU' // ObjC metadata update callback function
global ::= nominal-type 'Ms' // ObjC resilient class stub
global ::= nominal-type 'Mt' // Full ObjC resilient class stub (private)
global ::= module 'MXM' // module descriptor
global ::= context 'MXE' // extension descriptor
global ::= context 'MXX' // anonymous context descriptor
global ::= context identifier 'MXY' // anonymous context descriptor
global ::= type assoc-type-list 'MXA' // generic parameter ref (HISTORICAL)
global ::= protocol 'Mp' // protocol descriptor
global ::= protocol 'Hr' // protocol descriptor runtime record
global ::= nominal-type 'Hn' // nominal type descriptor runtime record
#if SWIFT_RUNTIME_VERSION >= 5.1
global ::= opaque-type-decl-name 'Ho' // opaque type descriptor runtime record
#endif
global ::= protocol-conformance 'Hc' // protocol conformance runtime record
global ::= global 'HF' // accessible function runtime record
global ::= nominal-type 'Mo' // class metadata immediate member base offset
global ::= type 'MF' // metadata for remote mirrors: field descriptor
global ::= type 'MB' // metadata for remote mirrors: builtin type descriptor
global ::= protocol-conformance 'MA' // metadata for remote mirrors: associated type descriptor
global ::= nominal-type 'MC' // metadata for remote mirrors: superclass descriptor
global ::= mangled-name 'TA' // partial application forwarder
global ::= mangled-name 'Ta' // ObjC partial application forwarder
global ::= mangled-name 'TQ' index // Async await continuation partial function
global ::= mangled-name 'TY' index // Async suspend continuation partial function
global ::= mangled-name 'TwS' // #_hasSymbol query function
global ::= type 'w' VALUE-WITNESS-KIND // value witness
global ::= protocol 'MS' // protocol self-conformance descriptor
global ::= protocol 'WS' // protocol self-conformance witness table
global ::= protocol-conformance 'Mc' // protocol conformance descriptor
global ::= protocol-conformance 'WP' // protocol witness table
global ::= protocol-conformance 'Wa' // protocol witness table accessor (HISTORICAL)
global ::= protocol-conformance 'WG' // generic protocol witness table (HISTORICAL)
global ::= protocol-conformance 'Wp' // protocol witness table pattern
global ::= protocol-conformance 'Wr' // resilient witness table (HISTORICAL)
global ::= protocol-conformance 'WI' // generic protocol witness table instantiation function
global ::= type protocol-conformance 'WL' // lazy protocol witness table cache variable
global ::= protocol-conformance identifier 'Wt' // associated type metadata accessor (HISTORICAL)
global ::= protocol-conformance assoc-type-list protocol 'WT' // associated type witness table accessor
global ::= protocol-conformance protocol 'Wb' // base protocol witness table accessor
global ::= type protocol-conformance 'Wl' // lazy protocol witness table accessor
global ::= global generic-signature? 'WJ' DIFFERENTIABILITY-KIND INDEX-SUBSET 'p' INDEX-SUBSET 'r' // differentiability witness
global ::= type 'WV' // value witness table
global ::= entity 'Wvd' // field offset
global ::= entity 'WC' // resilient enum tag index
global ::= global 'MK' // instantiation cache associated with global
global ::= global 'MJ' // noncanonical specialized generic type metadata instantiation cache associated with global
global ::= global 'MN' // noncanonical specialized generic type metadata for global
global ::= global 'Mz' // canonical specialized generic type metadata caching token
global ::= global 'Mq' // global with a uniquing prefix
#if SWIFT_RUNTIME_VERSION >= 5.4
global ::= context (decl-name '_')+ 'WZ' // global variable one-time initialization function
global ::= context (decl-name '_')+ 'Wz' // global variable one-time initialization token
#endif
A direct symbol resolves directly to the address of an object. An
indirect symbol resolves to the address of a pointer to the object.
They are distinct manglings to make a certain class of bugs
immediately obvious.
The terminology is slightly overloaded when discussing offsets. A
direct offset resolves to a variable holding the true offset. An
indirect offset resolves to a variable holding an offset to be applied
to type metadata to get the address of the true offset. (Offset
variables are required when the object being accessed lies within a
resilient structure. When the layout of the object may depend on
generic arguments, these offsets must be kept in metadata. Indirect
field offsets are therefore required when accessing fields in generic
types where the metadata itself has unknown layout.)
::
global ::= global 'Tj' // resilient method dispatch thunk
global ::= global 'Tq' // method descriptor
global ::= global 'TO' // ObjC-as-swift thunk
global ::= global 'To' // swift-as-ObjC thunk
global ::= global 'TD' // dynamic dispatch thunk
global ::= global 'Td' // direct method reference thunk
global ::= global 'TE' // distributed actor thunk
global ::= global 'TF' // distributed method accessor
global ::= global 'TI' // implementation of a dynamic_replaceable function
global ::= global 'Tu' // async function pointer of a function
global ::= global 'TX' // function pointer of a dynamic_replaceable function
global ::= global 'Twb' // back deployment thunk
global ::= global 'TwB' // back deployment fallback function
global ::= global 'Twc' // coro function pointer of a function
global ::= global 'Twd' // default override of a function
global ::= entity entity 'TV' // vtable override thunk, derived followed by base
global ::= type label-list? 'D' // type mangling for the debugger with label list for function types.
global ::= type 'TC' // continuation prototype (not actually used for real symbols)
global ::= protocol-conformance entity 'TW' // protocol witness thunk
global ::= entity 'TS' // protocol self-conformance witness thunk
global ::= context identifier identifier 'TB' // property behavior initializer thunk (not used currently)
global ::= context identifier identifier 'Tb' // property behavior setter thunk (not used currently)
global ::= global specialization // function specialization
global ::= global 'Tm' // merged function
global ::= entity // some identifiable thing
global ::= type type generic-signature? 'TR' // reabstraction thunk
global ::= impl-function-type type generic-signature? 'Tz' index? // objc-to-swift-async completion handler block implementation
global ::= impl-function-type type generic-signature? 'TZ' index? // objc-to-swift-async completion handler block implementation predefined by runtime
global ::= type type type generic-signature? 'Ty' // reabstraction thunk with dynamic 'Self' capture
global ::= type type generic-signature? 'Tr' // obsolete mangling for reabstraction thunk
global ::= entity generic-signature? type type* 'TK' // key path getter
global ::= entity generic-signature? type type* 'Tk' // key path setter
global ::= entity generic-signature? type type* 'Tkmu' // key path unapplied method
global ::= entity generic-signature? type type* 'TkMA' // key path applied method
global ::= type generic-signature 'TH' // key path equality
global ::= type generic-signature 'Th' // key path hasher
global ::= global generic-signature? 'TJ' AUTODIFF-FUNCTION-KIND INDEX-SUBSET 'p' INDEX-SUBSET 'r' // autodiff function
global ::= global generic-signature? 'TJV' AUTODIFF-FUNCTION-KIND INDEX-SUBSET 'p' INDEX-SUBSET 'r' // autodiff derivative vtable thunk
global ::= type type 'TJO' AUTODIFF-FUNCTION-KIND // autodiff self-reordering reabstraction thunk
global ::= type 'TJS' AUTODIFF-FUNCTION-KIND INDEX-SUBSET 'p' INDEX-SUBSET 'r' INDEX-SUBSET 'P' // autodiff linear map subset parameters thunk
global ::= global type 'TJS' AUTODIFF-FUNCTION-KIND INDEX-SUBSET 'p' INDEX-SUBSET 'r' INDEX-SUBSET 'P' // autodiff derivative function subset parameters thunk
global ::= protocol 'TL' // protocol requirements base descriptor
global ::= assoc-type-name 'Tl' // associated type descriptor
global ::= assoc-type-name 'TM' // default associated type witness accessor (HISTORICAL)
global ::= type assoc-type-list protocol 'Tn' // associated conformance descriptor
global ::= type assoc-type-list protocol 'TN' // default associated conformance witness accessor
global ::= type protocol 'Tb' // base conformance descriptor
REABSTRACT-THUNK-TYPE ::= 'R' // reabstraction thunk
REABSTRACT-THUNK-TYPE ::= 'r' // reabstraction thunk (obsolete)
global ::= global type 'TU' // reabstraction thunk with global actor constraint
All reabstraction thunks have the "from" and "to" types in that order, and
are always non-polymorphic ``<impl-function-type>`` types.
::
VALUE-WITNESS-KIND ::= 'al' // allocateBuffer
VALUE-WITNESS-KIND ::= 'ca' // assignWithCopy
VALUE-WITNESS-KIND ::= 'ta' // assignWithTake
VALUE-WITNESS-KIND ::= 'de' // deallocateBuffer
VALUE-WITNESS-KIND ::= 'xx' // destroy
VALUE-WITNESS-KIND ::= 'XX' // destroyBuffer
VALUE-WITNESS-KIND ::= 'Xx' // destroyArray
VALUE-WITNESS-KIND ::= 'CP' // initializeBufferWithCopyOfBuffer
VALUE-WITNESS-KIND ::= 'Cp' // initializeBufferWithCopy
VALUE-WITNESS-KIND ::= 'cp' // initializeWithCopy
VALUE-WITNESS-KIND ::= 'TK' // initializeBufferWithTakeOfBuffer
VALUE-WITNESS-KIND ::= 'Tk' // initializeBufferWithTake
VALUE-WITNESS-KIND ::= 'tk' // initializeWithTake
VALUE-WITNESS-KIND ::= 'pr' // projectBuffer
VALUE-WITNESS-KIND ::= 'xs' // storeExtraInhabitant
VALUE-WITNESS-KIND ::= 'xg' // getExtraInhabitantIndex
VALUE-WITNESS-KIND ::= 'Cc' // initializeArrayWithCopy
VALUE-WITNESS-KIND ::= 'Tt' // initializeArrayWithTakeFrontToBack
VALUE-WITNESS-KIND ::= 'tT' // initializeArrayWithTakeBackToFront
VALUE-WITNESS-KIND ::= 'ug' // getEnumTag
VALUE-WITNESS-KIND ::= 'up' // destructiveProjectEnumData
VALUE-WITNESS-KIND ::= 'ui' // destructiveInjectEnumTag
VALUE-WITNESS-KIND ::= 'et' // getEnumTagSinglePayload
VALUE-WITNESS-KIND ::= 'st' // storeEnumTagSinglePayload
``<VALUE-WITNESS-KIND>`` differentiates the kinds of value
witness functions for a type.
::
AUTODIFF-FUNCTION-KIND ::= 'f' // JVP (forward-mode derivative)
AUTODIFF-FUNCTION-KIND ::= 'r' // VJP (reverse-mode derivative)
AUTODIFF-FUNCTION-KIND ::= 'd' // differential
AUTODIFF-FUNCTION-KIND ::= 'p' // pullback
``<AUTODIFF-FUNCTION-KIND>`` differentiates the kinds of functions associated
with a differentiable function used for differentiable programming.
::
global ::= generic-signature? type 'WOy' // Outlined copy
global ::= generic-signature? type 'WOe' // Outlined consume
global ::= generic-signature? type 'WOr' // Outlined retain
global ::= generic-signature? type 'WOs' // Outlined release
global ::= generic-signature? type 'WOB' // Outlined initializeWithTake, not using value witness
global ::= generic-signature? type 'WOb' // Outlined initializeWithTake
global ::= generic-signature? type 'WOc' // Outlined initializeWithCopy
global ::= generic-signature? type 'WOC' // Outlined initializeWithCopy, not using value witness
global ::= generic-signature? type 'WOd' // Outlined assignWithTake
global ::= generic-signature? type 'WOD' // Outlined assignWithTake, not using value witness
global ::= generic-signature? type 'WOf' // Outlined assignWithCopy
global ::= generic-signature? type 'WOF' // Outlined assignWithCopy, not using value witness
global ::= generic-signature? type 'WOh' // Outlined destroy
global ::= generic-signature? type 'WOH' // Outlined destroy, not using value witness
global ::= generic-signature? type 'WOi' // Outlined store enum tag
global ::= generic-signature? type 'WOj' // Outlined enum destructive project
global ::= generic-signature? type 'WOg' // Outlined enum get tag
Entities
~~~~~~~~
::
entity ::= nominal-type // named type declaration
entity ::= context entity-spec static? curry-thunk?
static ::= 'Z'
curry-thunk ::= 'Tc'
label-list ::= empty-list // represents complete absence of parameter labels
label-list ::= label* // '_' is inserted as placeholder for empty label,
// since the number of labels should match the number of parameters
label ::= '_' // empty label
label ::= identifier // label
// The leading type is the function type
entity-spec ::= label-list type file-discriminator? 'fC' // allocating constructor
entity-spec ::= label-list type file-discriminator? 'fc' // non-allocating constructor
entity-spec ::= type 'fU' INDEX // explicit anonymous closure expression
entity-spec ::= type 'fu' INDEX // implicit anonymous closure
entity-spec ::= 'fA' INDEX // default argument N+1 generator
entity-spec ::= entity 'fa' // runtime discoverable attribute generator
entity-spec ::= 'fi' // non-local variable initializer
entity-spec ::= 'fP' // property wrapper backing initializer
entity-spec ::= 'fF' // property wrapped field init accessor
entity-spec ::= 'fW' // property wrapper init from projected value
entity-spec ::= 'fD' // deallocating destructor; untyped
entity-spec ::= 'fZ' // isolated deallocating destructor; untyped
entity-spec ::= 'fd' // non-deallocating destructor; untyped
entity-spec ::= 'fE' // ivar destroyer; untyped
entity-spec ::= 'fe' // ivar initializer; untyped
entity-spec ::= 'Tv' NATURAL // outlined global variable (from context function)
entity-spec ::= 'Tv' NATURAL 'r' // outlined global read-only object
entity-spec ::= 'Te' bridge-spec // outlined objective c method call
entity-spec ::= decl-name label-list function-signature generic-signature? 'F' // function
entity-spec ::= label-list type file-discriminator? 'i' ACCESSOR // subscript
entity-spec ::= decl-name label-list? type 'v' ACCESSOR // variable
entity-spec ::= decl-name type 'fp' // generic type parameter
entity-spec ::= decl-name type 'fo' // enum element (currently not used)
entity-spec ::= decl-name label-list? type generic-signature? 'fm' // macro
entity-spec ::= context macro-discriminator-list // macro expansion
entity-spec ::= identifier 'Qa' // associated type declaration
ACCESSOR ::= 'm' // materializeForSet
ACCESSOR ::= 's' // setter
ACCESSOR ::= 'g' // getter
ACCESSOR ::= 'G' // global getter
ACCESSOR ::= 'w' // willSet
ACCESSOR ::= 'W' // didSet
ACCESSOR ::= 'r' // _read
ACCESSOR ::= 'M' // _modify (temporary)
ACCESSOR ::= 'a' ADDRESSOR-KIND // mutable addressor
ACCESSOR ::= 'l' ADDRESSOR-KIND // non-mutable addressor
ACCESSOR ::= 'p' // pseudo accessor referring to the storage itself
ACCESSOR ::= 'x' // modify
ACCESSOR ::= 'y' // read
ACCESSOR ::= 'b' // borrow
ACCESSOR ::= 'z' // mutate
ADDRESSOR-KIND ::= 'u' // unsafe addressor (no owner)
ADDRESSOR-KIND ::= 'O' // owning addressor (non-native owner), not used anymore
ADDRESSOR-KIND ::= 'o' // owning addressor (native owner), not used anymore
ADDRESSOR-KIND ::= 'p' // pinning addressor (native owner), not used anymore
decl-name ::= identifier
decl-name ::= identifier 'L' INDEX // locally-discriminated declaration
decl-name ::= identifier identifier 'LL' // file-discriminated declaration
decl-name ::= identifier 'L' RELATED-DISCRIMINATOR // related declaration
RELATED-DISCRIMINATOR ::= [a-j]
RELATED-DISCRIMINATOR ::= [A-J]
macro-discriminator-list ::= macro-discriminator-list? file-discriminator? macro-expansion-operator INDEX
macro-expansion-operator ::= decl-name identifier 'fMa' // attached accessor macro
macro-expansion-operator ::= decl-name identifier 'fMr' // attached member-attribute macro
macro-expansion-operator ::= identifier 'fMf' // freestanding macro
macro-expansion-operator ::= decl-name identifier 'fMm' // attached member macro
macro-expansion-operator ::= decl-name identifier 'fMp' // attached peer macro
macro-expansion-operator ::= decl-name identifier 'fMc' // attached conformance macro
macro-expansion-operator ::= decl-name identifier 'fMe' // attached extension macro
macro-expansion-operator ::= decl-name identifier 'fMq' // attached preamble macro
macro-expansion-operator ::= decl-name identifier 'fMb' // attached body macro
macro-expansion-operator ::= decl-name identifier 'fMu' // uniquely-named entity
file-discriminator ::= identifier 'Ll' // anonymous file-discriminated declaration
The identifier in a ``<file-discriminator>`` and the second identifier in a
file-discriminated ``<decl-name>`` is a string that represents the file the
original declaration came from. It should be considered unique within the
enclosing module. The first identifier is the name of the entity. Not all
declarations marked ``private`` declarations will use this mangling; if the
entity's context is enough to uniquely identify the entity, the simple
``identifier`` form is preferred.
Twenty operators of the form 'LA', 'LB', etc. are reserved to described
entities related to the entity whose name is provided. For example, 'LE' and
'Le' in the "SC" module are used to represent the structs synthesized by the
Clang importer for various "error code" enums.
Outlined bridged Objective C method call mangling includes which parameters and
return value are bridged and the type of pattern outlined.
::
bridge-spec ::= bridged-kind bridged-param* bridged-return '_'
bridged-param ::= 'n' // not bridged parameter
bridged-param ::= 'b' // bridged parameter
bridged-return ::= 'n' // not bridged return
bridged-return ::= 'b' // bridged return
bridged-kind ::= 'm' // bridged method
bridged-kind ::= 'a' // bridged property (by address)
bridged-kind ::= 'p' // bridged property (by value)
Declaration Contexts
~~~~~~~~~~~~~~~~~~~~
These manglings identify the enclosing context in which an entity was declared,
such as its enclosing module, function, or nominal type.
::
context ::= module
context ::= entity
context ::= entity module generic-signature? 'E'
An ``extension`` mangling is used whenever an entity's declaration context is
an extension *and* the entity being extended is in a different module. In this
case the extension's module is mangled first, followed by the entity being
extended. If the extension and the extended entity are in the same module, the
plain ``entity`` mangling is preferred, but not always used. An extension is
considered "constrained" if it:
- Has any requirements not already satisfied by the extended nominal,
excluding conformance requirements for invertible protocols.
- Has any generic parameters with an inverse requirement.
Those requirements included in any of the above are included in the extension's
generic signature. The reason for this additional complexity is that we do not
mangle conformance req's for invertible protocols, only their absence.
::
struct S<A: ~Copyable, B: ~Copyable> {}
// An unconstrained extension.
extension S {}
// Also an unconstrained extension, because there are no inverses to mangle.
// This extension is exactly the same as the previous.
extension S where A: Copyable, B: Copyable {}
// A constrained extension, because of the added requirement `B: P` that is
// not already present in S.
extension S where B: P {}
// A constrained extension, because of the absence of `A: Copyable`.
// Despite also being absent in `S`, absences of invertible protocols
// are always mangled.
extension S where A: ~Copyable {}
Some entities, like computed properties, rely on the generic signature in their
`context`, so in order to disambiguate between those properties and
those in a context where a generic type requires Copyable, which is not mangled,
we have the following rule:
If the innermost type declaration for an entity has any inverses in its generic
signature, then extension mangling is used. This strategy is used to ensure
that moving a declaration between a nominal type and one of its extensions does
not cause an ABI break if the generic signature of the entity is equivalent in
both circumstances. For example:
::
struct R<A: ~Copyable> {
func f1() {} // uses extension mangling, just like `f3`
func f2() where A: Copyable {}
}
extension R where A: ~Copyable {
func f3() {}
func f4() where A: Copyable {} // uses entity mangling, just like `f2`
}
extension R where A: Copyable {
// 'f5' is mangled equivalent to 'f2' and 'f4' modulo its identifier.
func f5() {}
}
For intermediate nested types, i.e., those between the top level and the entity,
any inverses that remain in at the signature of the entity are mangled into
that entity's generic signature:
::
struct X<A: ~Copyable> {
struct Y<B: ~Copyable> {
// 'g1' uses 'entity' context mangling with and has no mangled signatures.
func g1() where A: Copyable, B: Copyable {}
// 'g2' uses 'entity' context mangling. The requirement `B: ~Copyable` is
//mangled into the generic signature for 'g2'.
func g2() where A: Copyable {}
// 'g3' uses extension mangling with generic signature 'A: ~Copyable'.
// The mangled generic signature of 'g3' is empty.
func g3() where B: Copyable {}
// 'g4' uses extension mangling with generic signature 'A: ~Copyable'.
// The mangled generic signature of 'g4' contains 'B: ~Copyable'.
func g4() {}
}
}
When mangling the context of a local entity within a constructor or
destructor, the non-allocating or non-deallocating variant is used.
::
module ::= identifier // module name
module ::= known-module // abbreviation
context ::= entity identifier type-list 'XZ' // unknown runtime context
The runtime produces manglings of unknown runtime contexts when a declaration
context has no preserved runtime information, or when a declaration is encoded
in runtime in a way that the current runtime does not understand. These
manglings are unstable and may change between runs of the process.
::
known-module ::= 's' // Swift
known-module ::= 'SC' // Clang-importer-synthesized
known-module ::= 'So' // C and Objective-C
The Objective-C module is used as the context for mangling Objective-C
classes as ``<type>``\ s.
Types
~~~~~
::
any-generic-type ::= substitution
any-generic-type ::= context decl-name 'C' // nominal class type
any-generic-type ::= context decl-name 'O' // nominal enum type
any-generic-type ::= context decl-name 'V' // nominal struct type
any-generic-type ::= context decl-name 'XY' // unknown nominal type
any-generic-type ::= protocol 'P' // nominal protocol type
any-generic-type ::= standard-substitutions
nominal-type ::= any-generic-type // nominal type
standard-substitutions ::= 'S' KNOWN-TYPE-KIND // known nominal type substitution
standard-substitutions ::= 'S' NATURAL KNOWN-TYPE-KIND // repeated known type substitutions of the same kind
KNOWN-TYPE-KIND ::= 'A' // Swift.AutoreleasingUnsafeMutablePointer
KNOWN-TYPE-KIND ::= 'a' // Swift.Array
KNOWN-TYPE-KIND ::= 'B' // Swift.BinaryFloatingPoint
KNOWN-TYPE-KIND ::= 'b' // Swift.Bool
KNOWN-TYPE-KIND ::= 'c' KNOWN-TYPE-KIND-2 // Second set of standard types
KNOWN-TYPE-KIND ::= 'D' // Swift.Dictionary
KNOWN-TYPE-KIND ::= 'd' // Swift.Float64
KNOWN-TYPE-KIND ::= 'E' // Swift.Encodable
KNOWN-TYPE-KIND ::= 'e' // Swift.Decodable
KNOWN-TYPE-KIND ::= 'F' // Swift.FloatingPoint
KNOWN-TYPE-KIND ::= 'f' // Swift.Float32
KNOWN-TYPE-KIND ::= 'G' // Swift.RandomNumberGenerator
KNOWN-TYPE-KIND ::= 'H' // Swift.Hashable
KNOWN-TYPE-KIND ::= 'h' // Swift.Set
KNOWN-TYPE-KIND ::= 'I' // Swift.DefaultIndices
KNOWN-TYPE-KIND ::= 'i' // Swift.Int
KNOWN-TYPE-KIND ::= 'J' // Swift.Character
KNOWN-TYPE-KIND ::= 'j' // Swift.Numeric
KNOWN-TYPE-KIND ::= 'K' // Swift.BidirectionalCollection
KNOWN-TYPE-KIND ::= 'k' // Swift.RandomAccessCollection
KNOWN-TYPE-KIND ::= 'L' // Swift.Comparable
KNOWN-TYPE-KIND ::= 'l' // Swift.Collection
KNOWN-TYPE-KIND ::= 'M' // Swift.MutableCollection
KNOWN-TYPE-KIND ::= 'm' // Swift.RangeReplaceableCollection
KNOWN-TYPE-KIND ::= 'N' // Swift.ClosedRange
KNOWN-TYPE-KIND ::= 'n' // Swift.Range
KNOWN-TYPE-KIND ::= 'O' // Swift.ObjectIdentifier
KNOWN-TYPE-KIND ::= 'P' // Swift.UnsafePointer
KNOWN-TYPE-KIND ::= 'p' // Swift.UnsafeMutablePointer
KNOWN-TYPE-KIND ::= 'Q' // Swift.Equatable
KNOWN-TYPE-KIND ::= 'q' // Swift.Optional
KNOWN-TYPE-KIND ::= 'R' // Swift.UnsafeBufferPointer
KNOWN-TYPE-KIND ::= 'r' // Swift.UnsafeMutableBufferPointer
KNOWN-TYPE-KIND ::= 'S' // Swift.String
KNOWN-TYPE-KIND ::= 's' // Swift.Substring
KNOWN-TYPE-KIND ::= 'T' // Swift.Sequence
KNOWN-TYPE-KIND ::= 't' // Swift.IteratorProtocol
KNOWN-TYPE-KIND ::= 'U' // Swift.UnsignedInteger
KNOWN-TYPE-KIND ::= 'u' // Swift.UInt
KNOWN-TYPE-KIND ::= 'V' // Swift.UnsafeRawPointer
KNOWN-TYPE-KIND ::= 'v' // Swift.UnsafeMutableRawPointer
KNOWN-TYPE-KIND ::= 'W' // Swift.UnsafeRawBufferPointer
KNOWN-TYPE-KIND ::= 'w' // Swift.UnsafeMutableRawBufferPointer
KNOWN-TYPE-KIND ::= 'X' // Swift.RangeExpression
KNOWN-TYPE-KIND ::= 'x' // Swift.Strideable
KNOWN-TYPE-KIND ::= 'Y' // Swift.RawRepresentable
KNOWN-TYPE-KIND ::= 'y' // Swift.StringProtocol
KNOWN-TYPE-KIND ::= 'Z' // Swift.SignedInteger
KNOWN-TYPE-KIND ::= 'z' // Swift.BinaryInteger
KNOWN-TYPE-KIND-2 ::= 'A' // Swift.Actor
KNOWN-TYPE-KIND-2 ::= 'C' // Swift.CheckedContinuation
KNOWN-TYPE-KIND-2 ::= 'c' // Swift.UnsafeContinuation
KNOWN-TYPE-KIND-2 ::= 'E' // Swift.CancellationError
KNOWN-TYPE-KIND-2 ::= 'e' // Swift.UnownedSerialExecutor
KNOWN-TYPE-KIND-2 ::= 'F' // Swift.Executor
KNOWN-TYPE-KIND-2 ::= 'f' // Swift.SerialExecutor
KNOWN-TYPE-KIND-2 ::= 'G' // Swift.TaskGroup
KNOWN-TYPE-KIND-2 ::= 'g' // Swift.ThrowingTaskGroup
KNOWN-TYPE-KIND-2 ::= 'I' // Swift.AsyncIteratorProtocol
KNOWN-TYPE-KIND-2 ::= 'i' // Swift.AsyncSequence
KNOWN-TYPE-KIND-2 ::= 'J' // Swift.UnownedJob
KNOWN-TYPE-KIND-2 ::= 'M' // Swift.MainActor
KNOWN-TYPE-KIND-2 ::= 'P' // Swift.TaskPriority
KNOWN-TYPE-KIND-2 ::= 'S' // Swift.AsyncStream
KNOWN-TYPE-KIND-2 ::= 's' // Swift.AsyncThrowingStream
KNOWN-TYPE-KIND-2 ::= 'T' // Swift.Task
KNOWN-TYPE-KIND-2 ::= 't' // Swift.UnsafeCurrentTask
protocol ::= context decl-name
protocol ::= standard-substitutions
type ::= 'Bb' // Builtin.BridgeObject
type ::= 'BB' // Builtin.UnsafeValueBuffer
#if SWIFT_RUNTIME_VERSION >= 5.5
type ::= 'Bc' // Builtin.RawUnsafeContinuation
type ::= 'BD' // Builtin.DefaultActorStorage
type ::= 'Be' // Builtin.Executor
#endif
#if SWIFT_RUNTIME_VERSION >= 5.9
type ::= 'Bd' // Builtin.NonDefaultDistributedActorStorage
#endif
type ::= 'Bf' NATURAL '_' // Builtin.Float<n>
type ::= 'Bi' NATURAL '_' // Builtin.Int<n>
type ::= 'BI' // Builtin.IntLiteral
#if SWIFT_RUNTIME_VERSION >= 5.5
type ::= 'Bj' // Builtin.Job
#endif
type ::= 'BP' // Builtin.PackIndex
type ::= 'BO' // Builtin.UnknownObject (no longer a distinct type, but still used for AnyObject)
type ::= 'Bo' // Builtin.NativeObject
type ::= 'Bp' // Builtin.RawPointer
type ::= 'Bt' // Builtin.SILToken
type ::= type 'Bv' NATURAL '_' // Builtin.Vec<n>x<type>
type ::= type type 'BV' // Builtin.FixedArray<N, T>
type ::= 'Bw' // Builtin.Word
#if SWIFT_RUNTIME_VERSION >= 6.2
type ::= 'BA' // Builtin.ImplicitActor
#endif
type ::= function-signature 'c' // function type (escaping)
type ::= function-signature 'X' FUNCTION-KIND // special function type
type ::= bound-generic-type
type ::= type 'Sg' // optional type, shortcut for: type 'ySqG'
type ::= type 'Xo' // @unowned type
type ::= type 'Xu' // @unowned(unsafe) type
type ::= type 'Xw' // @weak type
type ::= impl-function-type 'XF' // function implementation type (currently unused)
type ::= type 'Xb' // SIL @box type (deprecated)
type ::= type-list 'Xx' // SIL box type
type ::= type-list type-list generic-signature 'XX'
// Generic SIL box type
type ::= type 'XD' // dynamic self type
type ::= type 'm' // metatype without representation
type ::= type 'XM' METATYPE-REPR // metatype with representation
type ::= type 'Xp' // existential metatype without representation
type ::= type 'Xm' METATYPE-REPR // existential metatype with representation
type ::= 'Xe' // error or unresolved type
#if SWIFT_RUNTIME_VERSION >= 6.TBD
type ::= '$' 'n'? INDEX // integer type
#endif
bound-generic-type ::= type bound-generic-args 'G' // one type-list per nesting level of type
bound-generic-type ::= substitution
bound-generic-args ::= 'y' (type* '_')* type* retroactive-conformance* // generic arguments
FUNCTION-KIND ::= 'f' // @thin function type
FUNCTION-KIND ::= 'U' // uncurried function type (currently not used)
FUNCTION-KIND ::= 'K' // @auto_closure function type (noescape)
FUNCTION-KIND ::= 'B' // objc block function type
FUNCTION-KIND ::= 'zB' C-TYPE // objc block type with non-canonical C type
FUNCTION-KIND ::= 'L' // objc block function type with canonical C type (escaping) (DWARF only; otherwise use 'B' or 'zB' C-TYPE)
FUNCTION-KIND ::= 'C' // C function pointer / C++ method type
FUNCTION-KIND ::= 'zC' C-TYPE // C function pointer / C++ method type with non-canonical C type
FUNCTION-KIND ::= 'A' // @auto_closure function type (escaping)
FUNCTION-KIND ::= 'E' // function type (noescape)
C-TYPE ::= NATURAL IDENTIFIER-STRING // raw Itanium mangling
function-signature ::= result-type params-type async? sendable? throws? differentiable? function-isolation? sending-result? // results and parameters
result-type ::= type
result-type ::= empty-list // shortcut for ()
params-type ::= type 'z'? 'h'? // tuple in case of multiple parameters or a single parameter with a single tuple type
// with optional inout convention, shared convention. parameters don't have labels,
// they are mangled separately as part of the entity.
params-type ::= empty-list // shortcut for no parameters
#if SWIFT_RUNTIME_VERSION >= 5.5
async ::= 'Ya' // 'async' annotation on function types
sendable ::= 'Yb' // @Sendable on function types
function-isolation ::= type 'Yc' // Global actor on function type
#endif
throws ::= 'K' // 'throws' annotation on function types
#if SWIFT_RUNTIME_VERSION >= 6.0
throws ::= type 'YK' // 'throws(type)' annotation on function types
function-isolation ::= type 'YA' // @isolated(any) on function type
sending-result ::= 'YT' // -> sending T
#endif
#if SWIFT_RUNTIME_VERSION >= 6.2
function-isolation :== 'YC' // nonisolated(nonsending) on function type
#endif
differentiable ::= 'Yjf' // @differentiable(_forward) on function type
differentiable ::= 'Yjr' // @differentiable(reverse) on function type
differentiable ::= 'Yjd' // @differentiable on function type
differentiable ::= 'Yjl' // @differentiable(_linear) on function type
type-list ::= list-type '_' list-type* // list of types
type-list ::= empty-list
// FIXME: Consider replacing 'h' with a two-char code
list-type ::= type identifier? 'Yk'? 'z'? 'h'? 'n'? 'Yi'? 'd'? 'Yt'? // type with optional label, '@noDerivative', inout convention, shared convention, owned convention, actor 'isolated', variadic specifier, and compile-time constant
In the mangling of C function types,``C-TYPE`` is mangled according to the Itanium ABI, prefixed with its length. This resembles the mangling of ``identifier``, but it does not honor substitutions or Punycode.
The 6.0 Swift runtime supports demangling ``sending-result``, but has a bug when it's combined with ``function-isolation``.
::
METATYPE-REPR ::= 't' // Thin metatype representation
METATYPE-REPR ::= 'T' // Thick metatype representation
METATYPE-REPR ::= 'o' // ObjC metatype representation
existential-layout ::= protocol-list 'p' // existential layout
existential-layout ::= protocol-list type 'Xc' // existential layout with superclass
existential-layout ::= protocol-list 'Xl' // existential layout with AnyObject
type ::= associated-type
type ::= any-generic-type
type ::= existential-layout // existential type
type ::= existential-layout requirement '_' requirement* 'XP' // constrained existential type
type ::= type-list 't' // tuple
type ::= type generic-signature 'u' // generic type
type ::= 'x' // generic param, depth=0, idx=0
type ::= 'q' GENERIC-PARAM-INDEX // dependent generic parameter
type ::= type assoc-type-name 'qa' // associated type of non-generic param
type ::= assoc-type-name 'Qy' GENERIC-PARAM-INDEX // associated type
type ::= assoc-type-name 'Qz' // shortcut for 'Qyz'
type ::= assoc-type-list 'QY' GENERIC-PARAM-INDEX // associated type at depth
type ::= assoc-type-list 'QZ' // shortcut for 'QYz'
type ::= type 'Qe' INDEX // pack element type
type ::= type type 'Qp' // pack expansion type (pattern, count)
type ::= pack-element-list 'QP' // pack type
type ::= pack-element-list 'QS' DIRECTNESS // SIL pack type
pack-element-list ::= type '_' type*
pack-element-list ::= empty-list
#if SWIFT_RUNTIME_VERSION >= 5.2
type ::= type assoc-type-name 'Qx' // associated type relative to base `type`
type ::= type assoc-type-list 'QX' // associated type relative to base `type` list
#endif
#if SWIFT_RUNTIME_VERSION >= 5.7
type ::= symbolic-extended-existential-type-shape type* retroactive-conformance* 'Xj'
#endif
protocol-list ::= protocol '_' protocol*
protocol-list ::= empty-list
assoc-type-list ::= assoc-type-name '_' assoc-type-name*
associated-type ::= substitution
associated-type ::= type identifier 'Qa' // associated type
assoc-type-name ::= identifier // associated type name without protocol
assoc-type-name ::= identifier protocol 'P' // associated type name with protocol
empty-list ::= 'y'
Associated types use an abbreviated mangling when the base generic parameter
or associated type is constrained by a single protocol requirement. The
associated type in this case can be referenced unambiguously by name alone.
If the base has multiple conformance constraints, then the protocol name is
mangled in to disambiguate.
::
impl-function-type ::= type* 'I' FUNC-ATTRIBUTES '_'
impl-function-type ::= type* generic-signature 'I' FUNC-ATTRIBUTES '_'
FUNC-ATTRIBUTES ::= PATTERN-SUBS? INVOCATION-SUB? PSEUDO-GENERIC? CALLEE-ESCAPE? ISOLATION? DIFFERENTIABILITY-KIND? CALLEE-CONVENTION FUNC-REPRESENTATION? COROUTINE-KIND? SENDABLE? ASYNC? SENDING-RESULT? (PARAM-CONVENTION PARAM-DIFFERENTIABILITY?)* RESULT-CONVENTION* ('Y' PARAM-CONVENTION)* ('z' RESULT-CONVENTION RESULT-DIFFERENTIABILITY?)?
PATTERN-SUBS ::= 's' // has pattern substitutions
INVOCATION-SUB ::= 'I' // has invocation substitutions
PSEUDO-GENERIC ::= 'P'
CALLEE-ESCAPE ::= 'e' // @escaping (inverse of SIL @noescape)
ISOLATION ::= 'A' // @isolated(any)
DIFFERENTIABILITY-KIND ::= 'd' // @differentiable
DIFFERENTIABILITY-KIND ::= 'l' // @differentiable(_linear)
DIFFERENTIABILITY-KIND ::= 'f' // @differentiable(_forward)
DIFFERENTIABILITY-KIND ::= 'r' // @differentiable(reverse)
CALLEE-CONVENTION ::= 'y' // @callee_unowned
CALLEE-CONVENTION ::= 'g' // @callee_guaranteed
CALLEE-CONVENTION ::= 'x' // @callee_owned
CALLEE-CONVENTION ::= 't' // thin
FUNC-REPRESENTATION ::= 'B' // C block invocation function
FUNC-REPRESENTATION ::= 'zB' C-TYPE // C block invocation function with non-canonical C type
FUNC-REPRESENTATION ::= 'C' // C global function
FUNC-REPRESENTATION ::= 'zC' C-TYPE // C global function with non-canonical C type
FUNC-REPRESENTATION ::= 'M' // Swift method
FUNC-REPRESENTATION ::= 'J' // ObjC method
FUNC-REPRESENTATION ::= 'K' // closure
FUNC-REPRESENTATION ::= 'W' // protocol witness
COROUTINE-KIND ::= 'A' // yield-once coroutine
COROUTINE-KIND ::= 'I' // yield-once-2 coroutine
COROUTINE-KIND ::= 'G' // yield-many coroutine
#if SWIFT_RUNTIME_VERSION >= 5.5
SENDABLE ::= 'h' // @Sendable
ASYNC ::= 'H' // @async
#endif
#if SWIFT_RUNTIME_VERSION >= 6.0
SENDING-RESULT ::= 'T' // sending result
#endif
PARAM-CONVENTION ::= 'i' // indirect in
PARAM-CONVENTION ::= 'c' // indirect in constant
PARAM-CONVENTION ::= 'l' // indirect inout
PARAM-CONVENTION ::= 'b' // indirect inout aliasable
PARAM-CONVENTION ::= 'n' // indirect in guaranteed
PARAM-CONVENTION ::= 'X' // indirect in C++
PARAM-CONVENTION ::= 'x' // direct owned
PARAM-CONVENTION ::= 'y' // direct unowned
PARAM-CONVENTION ::= 'g' // direct guaranteed
PARAM-CONVENTION ::= 'e' // direct deallocating
PARAM-CONVENTION ::= 'v' // pack owned
PARAM-CONVENTION ::= 'p' // pack guaranteed
PARAM-CONVENTION ::= 'm' // pack inout
#if SWIFT_RUNTIME_VERSION >= 6.0
SENDING-PARAM ::= 'T' // sending parameter
#endif
#if SWIFT_RUNTIME_VERSION >= 6.2
ISOLATED-PARAM ::= 'I' // @isolated parameter
IMPLICIT-LEADING-PARAM ::= 'L' // @implicit_leading parameter
#endif
PARAM-DIFFERENTIABILITY ::= 'w' // @noDerivative
RESULT-CONVENTION ::= 'r' // indirect
RESULT-CONVENTION ::= 'o' // owned
RESULT-CONVENTION ::= 'd' // unowned
RESULT-CONVENTION ::= 'u' // unowned inner pointer
RESULT-CONVENTION ::= 'a' // auto-released
RESULT-CONVENTION ::= 'k' // pack
RESULT-CONVENTION ::= 'l' // guaranteed address
RESULT-CONVENTION ::= 'g' // guaranteed
RESULT-CONVENTION ::= 'm' // inout
RESULT-DIFFERENTIABILITY ::= 'w' // @noDerivative
DIRECTNESS ::= 'i' // indirect
DIRECTNESS ::= 'd' // direct
For the most part, manglings follow the structure of formal language
types. However, in some cases it is more useful to encode the exact
implementation details of a function type.
::
#if SWIFT_VERSION >= 5.1
type ::= 'Qr' // opaque result type (of current decl, used for the first opaque type parameter only)
type ::= 'QR' INDEX // same as above, for subsequent opaque type parameters, INDEX is the ordinal -1
type ::= opaque-type-decl-name bound-generic-args 'Qo' INDEX // opaque type
opaque-type-decl-name ::= entity 'QO' // opaque result type of specified decl
#endif
#if SWIFT_VERSION >= 5.4
type ::= 'Qu' // opaque result type (of current decl, first param)
// used for ObjC class runtime name purposes.
type ::= 'QU' INDEX
#endif
Opaque return types have a special short representation in the mangling of
their defining entity. In structural position, opaque types are fully qualified
by mangling the defining entity for the opaque declaration and the substitutions
into the defining entity's generic environment.
The ``type*`` list contains parameter and return types (including the error
result), in that order.
The number of parameters and results must match with the number of
``<PARAM-CONVENTION>`` and ``<RESULT-CONVENTION>`` characters after the
``<FUNC-REPRESENTATION>``.
The ``<generic-signature>`` is used if the function is polymorphic.
DWARF debug info and USRs also mangle sugared types, adding the following
productions:
::
any-generic-type ::= context decl-name 'a' // typealias type
type ::= type 'XSq' // sugared Optional type
type ::= type 'XSa' // sugared Array type
type ::= type type 'XSD' // sugared Dictionary type (key, value)
type ::= type type 'XSA' // sugared InlineArray type (count, element)
Generics
~~~~~~~~
::
protocol-conformance-context ::= protocol module generic-signature?
protocol-conformance ::= type protocol-conformance-context
``<protocol-conformance>`` refers to a type's conformance to a protocol. The
named module is the one containing the extension or type declaration that
declared the conformance.
::
protocol-conformance ::= type protocol
If ``type`` is a generic parameter or associated type of one, then no module
is mangled, because the conformance must be resolved from the generic
environment.
protocol-conformance ::= context identifier protocol identifier generic-signature? // Property behavior conformance
Property behaviors are implemented using private protocol conformances.
::
concrete-protocol-conformance ::= type protocol-conformance-ref any-protocol-conformance-list 'HC'
protocol-conformance-ref ::= protocol 'HP' // same module as conforming type
protocol-conformance-ref ::= protocol 'Hp' // same module as protocol
protocol-conformance-ref ::= protocol module // "retroactive"
any-protocol-conformance ::= concrete-protocol-conformance
any-protocol-conformance ::= dependent-protocol-conformance
any-protocol-conformance ::= pack-protocol-conformance
any-protocol-conformance-list ::= any-protocol-conformance '_' any-protocol-conformance-list
any-protocol-conformance-list ::= empty-list
DEPENDENT-CONFORMANCE-INDEX ::= INDEX
dependent-protocol-conformance ::= type protocol 'HD' DEPENDENT-CONFORMANCE-INDEX
dependent-protocol-conformance ::= dependent-protocol-conformance protocol 'HI' DEPENDENT-CONFORMANCE-INDEX
dependent-protocol-conformance ::= dependent-protocol-conformance
dependent-associated-conformance 'HA' DEPENDENT-CONFORMANCE-INDEX
dependent-associated-conformance ::= type protocol
dependent-protocol-conformance ::= dependent-protocol-conformance type 'HO'
pack-protocol-conformance ::= any-protocol-conformance-list 'HX'
A compact representation used to represent mangled protocol conformance witness
arguments at runtime. The ``module`` is only specified for conformances that
are "retroactive", meaning that the context in which the conformance is defined
is in neither the protocol or type module. For a non-retroactive conformance
where both the type *and* the protocol are in the same module, or for
synthesized conformances that have no owning module, the "HP" operator is
preferred. The concrete protocol conformances that follow are for the
conditional conformance requirements.
Dependent protocol conformances mangle the access path required to extract a
protocol conformance from some conformance passed into the environment. The
first case (operator "HD") is the leaf requirement, containing a dependent type
and the protocol it conforms to. The remaining dependent protocol conformance
manglings describe lookups performed on their child dependent protocol
conformances. The "HI" operator retrieves the named inherited protocol from the
witness table produced by the child. The "HA" operator refers to an associated
conformance within the witness table, identified by the dependent type and
protocol. In all cases, the DEPENDENT-CONFORMANCE-INDEX is an INDEX value
indicating the position of the appropriate value within the generic environment
(for "HD") or witness table (for "HI" and "HA") when it is known to be at a
fixed position. An index of 1 ("0\_") is used to indicate "unknown"; all other
values are adjusted by 2. That these indexes are not 0-based is a bug that's
now codified into the ABI; the index 0 is therefore reserved.
::
generic-signature ::= requirement* generic-param-marker 'l' // one generic parameter
generic-signature ::= requirement* generic-param-marker* 'r' GENERIC-PARAM-COUNT* 'l'
generic-param-marker ::= generic-param-pack-marker
generic-param-marker ::= generic-param-value-marker
generic-param-pack-marker ::= 'Rv' GENERIC-PARAM-INDEX // generic parameter pack marker
#if SWIFT_RUNTIME_VERSION >= 6.TBD
generic-param-value-marker ::= type 'RV' GENERIC-PARAM-INDEX // generic parameter value marker
#endif
GENERIC-PARAM-COUNT ::= 'z' // zero parameters
GENERIC-PARAM-COUNT ::= INDEX // N+1 parameters
requirement ::= protocol 'R' GENERIC-PARAM-INDEX // protocol requirement
requirement ::= protocol assoc-type-name 'Rp' GENERIC-PARAM-INDEX // protocol requirement on associated type
requirement ::= protocol assoc-type-list 'RP' GENERIC-PARAM-INDEX // protocol requirement on associated type at depth
requirement ::= protocol substitution 'RQ' // protocol requirement with substitution
#if SWIFT_RUNTIME_VERSION >= 6.0
requirement ::= 'Ri' INDEX GENERIC-PARAM-INDEX // inverse requirement on generic parameter where INDEX is the bit number
requirement ::= substitution 'RI' INDEX // inverse requirement with substitution
requirement ::= assoc-type-name 'Rj' INDEX GENERIC-PARAM-INDEX // inverse requirement on associated type
requirement ::= assoc-type-list 'RJ' INDEX GENERIC-PARAM-INDEX // inverse requirement on associated type at depth
#endif
requirement ::= type 'Rb' GENERIC-PARAM-INDEX // base class requirement
requirement ::= type assoc-type-name 'Rc' GENERIC-PARAM-INDEX // base class requirement on associated type
requirement ::= type assoc-type-list 'RC' GENERIC-PARAM-INDEX // base class requirement on associated type at depth
requirement ::= type substitution 'RB' // base class requirement with substitution
requirement ::= type 'Rs' GENERIC-PARAM-INDEX // same-type requirement
requirement ::= type assoc-type-name 'Rt' GENERIC-PARAM-INDEX // same-type requirement on associated type
requirement ::= type assoc-type-list 'RT' GENERIC-PARAM-INDEX // same-type requirement on associated type at depth
requirement ::= type substitution 'RS' // same-type requirement with substitution
requirement ::= type 'Rl' GENERIC-PARAM-INDEX LAYOUT-CONSTRAINT // layout requirement
requirement ::= type assoc-type-name 'Rm' GENERIC-PARAM-INDEX LAYOUT-CONSTRAINT // layout requirement on associated type
requirement ::= type assoc-type-list 'RM' GENERIC-PARAM-INDEX LAYOUT-CONSTRAINT // layout requirement on associated type at depth
requirement ::= type substitution 'RM' LAYOUT-CONSTRAINT // layout requirement with substitution
requirement ::= type 'Rh' GENERIC-PARAM-INDEX // same-shape requirement (only supported on a generic parameter)
GENERIC-PARAM-INDEX ::= 'z' // depth = 0, idx = 0
GENERIC-PARAM-INDEX ::= INDEX // depth = 0, idx = N+1
GENERIC-PARAM-INDEX ::= 'd' INDEX INDEX // depth = M+1, idx = N
GENERIC-PARAM-INDEX ::= 's' // depth = 0, idx = 0; Constrained existential 'Self' type
LAYOUT-CONSTRAINT ::= 'N' // NativeRefCountedObject
LAYOUT-CONSTRAINT ::= 'R' // RefCountedObject
LAYOUT-CONSTRAINT ::= 'T' // Trivial
LAYOUT-CONSTRAINT ::= 'C' // Class
LAYOUT-CONSTRAINT ::= 'D' // NativeClass
LAYOUT-CONSTRAINT ::= 'E' LAYOUT-SIZE-AND-ALIGNMENT // Trivial of exact size and alignment
LAYOUT-CONSTRAINT ::= 'e' LAYOUT-SIZE // Trivial of exact size
LAYOUT-CONSTRAINT ::= 'M' LAYOUT-SIZE-AND-ALIGNMENT // Trivial of size and alignment at most N bits
LAYOUT-CONSTRAINT ::= 'm' LAYOUT-SIZE // Trivial of size at most N bits
LAYOUT-CONSTRAINT ::= 'U' // Unknown layout
LAYOUT-CONSTRAINT ::= 'B' // BridgeObject
LAYOUT-CONSTRAINT ::= 'S' // TrivialStride
LAYOUT-SIZE ::= INDEX // Size only
LAYOUT-SIZE-AND-ALIGNMENT ::= INDEX INDEX // Size followed by alignment
A generic signature begins with an optional list of requirements.
This is followed by an optional list of generic-param-pack-markers to record
which generic parameters are packs (variadic).
The ``<GENERIC-PARAM-COUNT>`` describes the number of generic parameters at
each depth of the signature. As a special case, no ``<GENERIC-PARAM-COUNT>``
values indicates a single generic parameter at the outermost depth::
x_xCru // <T_0_0> T_0_0 -> T_0_0
d_0__xCr_0_u // <T_0_0><T_1_0, T_1_1> T_0_0 -> T_1_1
A generic signature must only precede an operator character which is different
from any character in a ``<GENERIC-PARAM-COUNT>``.
::
retroactive-conformance ::= any-protocol-conformance 'g' INDEX
When a protocol conformance used to satisfy one of a bound generic type's
generic requirements is retroactive (i.e., it is specified in a module other
than the module of the conforming type or the conformed-to protocol), it is
mangled with its offset into the set of conformance requirements, the
root protocol conformance, and the suffix 'g'.
::
// No generalization signature.
extended-existential-shape ::= type 'Xg' // no generalization signature
extended-existential-shape ::= generic-signature type 'XG'
Identifiers
~~~~~~~~~~~
::
identifier ::= substitution
identifier ::= NATURAL IDENTIFIER-STRING // identifier without word substitutions
identifier ::= '0' IDENTIFIER-PART // identifier with word substitutions
IDENTIFIER-PART ::= NATURAL IDENTIFIER-STRING
IDENTIFIER-PART ::= [a-z] // word substitution (except the last one)
IDENTIFIER-PART ::= [A-Z] // last word substitution in identifier
IDENTIFIER-STRING ::= IDENTIFIER-START-CHAR IDENTIFIER-CHAR*
IDENTIFIER-START-CHAR ::= [_a-zA-Z]
IDENTIFIER-CHAR ::= [_$a-zA-Z0-9]
``<identifier>`` is run-length encoded: the natural indicates how many
characters follow. Operator characters are mapped to letter characters as
given. In neither case can an identifier start with a digit, so
there's no ambiguity with the run-length.
If the run-length start with a ``0`` the identifier string contains
word substitutions. A word is a sub-string of an identifier which contains
letters and digits ``[A-Za-z0-9]``. Words are separated by underscores
``_``. In addition a new word begins with an uppercase letter ``[A-Z]``
if the previous character is not an uppercase letter::
Abc1DefG2HI // contains four words 'Abc1', 'Def' and 'G2' and 'HI'
_abc1_def_G2hi // contains three words 'abc1', 'def' and G2hi
The words of all identifiers, which are encoded in the current mangling are
enumerated and assigned to a letter: a = first word, b = second word, etc.
An identifier containing word substitutions is a sequence of run-length encoded
sub-strings and references to previously mangled words.
All but the last word-references are lowercase letters and the last one is an
uppercase letter. If there is no literal sub-string after the last
word-reference, the last word-reference is followed by a ``0``.
Let's assume the current mangling already encoded the identifier ``AbcDefGHI``::
02Myac1_B // expands to: MyAbcGHI_Def
A maximum of 26 words in a mangling can be used for substitutions.
::
identifier ::= '00' natural '_'? IDENTIFIER-CHAR+ // '_' is inserted if the identifier starts with a digit or '_'.
Identifiers that contain non-ASCII characters are encoded using the Punycode
algorithm specified in RFC 3492, with the modifications that ``_`` is used
as the encoding delimiter, and uppercase letters A through J are used in place
of digits 0 through 9 in the encoding character set. The mangling then
consists of an ``00`` followed by the run length of the encoded string and the
encoded string itself. For example, the identifier ``vergüenza`` is mangled
to ``0012vergenza_JFa``. (The encoding in standard Punycode would be
``vergenza-95a``)
If the encoded string starts with a digit or an ``_``, an additional ``_`` is
inserted between the run length and the encoded string.
::
identifier ::= identifier 'o' OPERATOR-FIXITY
OPERATOR-FIXITY ::= 'p' // prefix operator
OPERATOR-FIXITY ::= 'P' // postfix operator
OPERATOR-FIXITY ::= 'i' // infix operator
OPERATOR-CHAR ::= 'a' // & 'and'
OPERATOR-CHAR ::= 'c' // @ 'commercial at'
OPERATOR-CHAR ::= 'd' // / 'divide'
OPERATOR-CHAR ::= 'e' // = 'equals'
OPERATOR-CHAR ::= 'g' // > 'greater'
OPERATOR-CHAR ::= 'l' // < 'less'
OPERATOR-CHAR ::= 'm' // * 'multiply'
OPERATOR-CHAR ::= 'n' // ! 'not'
OPERATOR-CHAR ::= 'o' // | 'or'
OPERATOR-CHAR ::= 'p' // + 'plus'
OPERATOR-CHAR ::= 'q' // ? 'question'
OPERATOR-CHAR ::= 'r' // % 'remainder'
OPERATOR-CHAR ::= 's' // - 'subtract'
OPERATOR-CHAR ::= 't' // ~ 'tilde'
OPERATOR-CHAR ::= 'x' // ^ 'xor'
OPERATOR-CHAR ::= 'z' // . 'zperiod'
If an identifier is followed by an ``o`` its text is interpreted as an
operator. Each lowercase character maps to an operator character
(``OPERATOR-CHAR``).
Operators that contain non-ASCII characters are mangled by first mapping the
ASCII operator characters to letters as for pure ASCII operator names, then
Punycode-encoding the substituted string.
For example, the infix operator ``«+»`` is mangled to
``007p_qcaDcoi`` (``p_qcaDc`` being the encoding of the substituted
string ``«p»``).
Substitutions
~~~~~~~~~~~~~
::
substitution ::= 'A' INDEX // substitution of N+26
substitution ::= 'A' SUBST-IDX* LAST-SUBST-IDX // One or more consecutive substitutions of N < 26
SUBST-IDX ::= [a-z]
SUBST-IDX ::= NATURAL [a-z]
LAST-SUBST-IDX ::= [A-Z]
LAST-SUBST-IDX ::= NATURAL [A-Z]
``<substitution>`` is a back-reference to a previously mangled entity. The mangling
algorithm maintains a mapping of entities to substitution indices as it runs.
When an entity that can be represented by a substitution (a module, nominal
type, or protocol) is mangled, a substitution is first looked for in the
substitution map, and if it is present, the entity is mangled using the
associated substitution index. Otherwise, the entity is mangled normally, and
it is then added to the substitution map and associated with the next
available substitution index.
For example, in mangling a function type
``(zim.zang.zung, zim.zang.zung, zim.zippity) -> zim.zang.zoo`` (with module
``zim`` and class ``zim.zang``),
the recurring contexts ``zim``, ``zim.zang``, and ``zim.zang.zung``
will be mangled using substitutions after being mangled
for the first time. The first argument type will mangle in long form,
``3zim4zang4zung``, and in doing so, ``zim`` will acquire substitution ``AA``,
``zim.zang`` will acquire substitution ``AB``, and ``zim.zang.zung`` will
acquire ``AC``. The second argument is the same as the first and will mangle
using its substitution, ``AC``. The
third argument type will mangle using the substitution for ``zim``,
``AA7zippity``. (It also acquires substitution ``AD`` which would be used
if it mangled again.) The result type will mangle using the substitution for
``zim.zang``, ``AB3zoo`` (and acquire substitution ``AE``).
There are some pre-defined substitutions, see ``KNOWN-TYPE-KIND``.
If the mangling contains two or more consecutive substitutions, it can be
abbreviated with the ``A`` substitution. Similar to word-substitutions the
index is encoded as letters, whereas the last letter is uppercase::
AaeB // equivalent to A_A4_A0_
Repeated substitutions are encoded with a natural prefix number::
A3a2B // equivalent to AaaabB
Numbers and Indexes
~~~~~~~~~~~~~~~~~~~
::
INDEX ::= '_' // 0
INDEX ::= NATURAL '_' // N+1
NATURAL ::= [1-9] [0-9]*
NATURAL-ZERO ::= [0-9]+
``<INDEX>`` is a production for encoding numbers in contexts that can't
end in a digit; it's optimized for encoding smaller numbers.
::
INDEX-SUBSET ::= [SU]+
``<INDEX-SUBSET>`` is encoded like a bit vector and is optimized for encoding
indices with a small upper bound.
Function Specializations
~~~~~~~~~~~~~~~~~~~~~~~~
::
specialization ::= type '_' type* 'T' dropped-arg* 'g' SPEC-INFO // Generic re-abstracted specialization
specialization ::= type '_' type* 'T' dropped-arg* 'B' SPEC-INFO // Alternative mangling for generic re-abstracted specializations,
// used for functions with re-abstracted resilient parameter types.
specialization ::= type '_' type* 'T' dropped-arg* 'G' SPEC-INFO // Generic not re-abstracted specialization
specialization ::= type '_' type* 'Ts' SPEC-INFO // Generic re-abstracted prespecialization
specialization ::= type '_' type* 'Ti' SPEC-INFO // Inlined function with generic substitutions.
specialization ::= type '_' type* 'Ta' SPEC-INFO // Non-async specialization
dropped-arg ::= 't' // The first argument is dropped
dropped-arg ::= 't' NATURAL // The `N+1`th argument is dropped
The types are the replacement types of the substitution list.
::
specialization ::= type 'Tp' SPEC-INFO // Partial generic specialization
specialization ::= type 'TP' SPEC-INFO // Partial generic specialization, not re-abstracted
The type is the function type of the specialized function.
::
specialization ::= spec-arg* 'Tf' SPEC-INFO ARG-SPEC-KIND* '_' ARG-SPEC-KIND // Function signature specialization kind
The ``<ARG-SPEC-KIND>`` describes how arguments are specialized.
Some kinds need arguments, which precede ``Tf``.
::
spec-arg ::= identifier
spec-arg ::= type
SPEC-INFO ::= FRAGILE? (ASYNC-REMOVED|REPR-CHANGED)? PASSID
PASSID ::= '0' // AllocBoxToStack,
PASSID ::= '1' // ClosureSpecializer,
PASSID ::= '2' // CapturePromotion,
PASSID ::= '3' // CapturePropagation,
PASSID ::= '4' // FunctionSignatureOpts,
PASSID ::= '5' // GenericSpecializer,
PASSID ::= '6' // MoveDiagnosticInOutToOut,
PASSID ::= '7' // AsyncDemotion,
PASSID ::= '8' // PackSpecialization,
PASSID ::= '9' // EmbeddedWitnessCallSpecialization
FRAGILE ::= 'q'
ASYNC-REMOVED ::= 'a' // async effect removed
REPR-CHANGED ::= 'r' // function type representation changed
ARG-SPEC-KIND ::= 'n' // Unmodified argument
ARG-SPEC-KIND ::= 'c' // Consumes n 'type' arguments which are closed over types in argument order
// and one 'identifier' argument which is the closure symbol name
ARG-SPEC-KIND ::= 'C' NATURAL-ZERO // the same closure as a previous argument <n>
ARG-SPEC-KIND ::= 'p' CONST-PROP // Constant propagated argument
ARG-SPEC-KIND ::= 'e' 'D'? 'G'? 'X'? // Generic argument, with optional dead, owned=>guaranteed or exploded-specifier
ARG-SPEC-KIND ::= 'd' 'G'? 'X'? // Dead argument, with optional owned=>guaranteed or exploded-specifier
ARG-SPEC-KIND ::= 'g' 'X'? // Owned => Guaranteed,, with optional exploded-specifier
ARG-SPEC-KIND ::= 'x' // Exploded
ARG-SPEC-KIND ::= 'i' // Box to value
ARG-SPEC-KIND ::= 's' // Box to stack
CONST-PROP ::= 'f' // Consumes one identifier argument which is a function symbol name
CONST-PROP ::= 'g' // Consumes one identifier argument which is a global symbol name
CONST-PROP ::= 'i' NATURAL-ZERO // 64-bit-integer
CONST-PROP ::= 'd' NATURAL-ZERO // float-as-64-bit-integer
CONST-PROP ::= 's' ENCODING // string literal. Consumes one identifier argument.
CONST-PROP ::= 'k' // keypath. Consumes one identifier - the SHA1 of the keypath and two types (root and value).
CONST-PROP ::= 'S' CONST-PROP* // struct with operands. Consumes one type argument - the struct type.
ENCODING ::= 'b' // utf8
ENCODING ::= 'w' // utf16
ENCODING ::= 'c' // objc
If the first character of the string literal is a digit ``[0-9]`` or an
underscore ``_``, the identifier for the string literal is prefixed with an
additional underscore ``_``.
Conventions for foreign symbols
-------------------------------
Swift interoperates with multiple other languages - C, C++, Objective-C, and
Objective-C++. Each of these languages defines their own mangling conventions,
so Swift must take care to follow them. However, these conventions do not cover
Swift-specific symbols like Swift type metadata for foreign types, so Swift uses
its own mangling scheme for those symbols.
Importing C and C++ structs
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Types imported from C and C++ are imported as if they are located in the ``__C``
module, regardless of the actual Clang module that they are coming from. This
can be observed when mangling a Swift function that accepts a C/C++ struct as a
parameter:
C++ module ``CxxStructModule``:
.. code-block:: c++
struct CxxStruct {};
inline void cxxFunction(CxxStruct s) {}
Swift module ``main`` that imports ``CxxStructModule``:
.. code-block:: swift
import CxxStructModule
public func swiftFunction(_ s: CxxStruct) {}
Resulting symbols (showing only Itanium-mangled C++ symbols for brevity):
.. code::
_Z11cxxFunction9CxxStruct // -> cxxFunction(CxxStruct)
s4main13swiftFunctionyySo9CxxStructVF // -> main.swiftFunction(__C.CxxStruct) -> ()
The reason for ignoring the Clang module and always putting C and C++ types into
``__C`` at the Swift ABI level is that the Clang module is not a part of the C
or C++ ABI. When owners of C and C++ Clang modules decide what changes are
ABI-compatible or not, they will likely take into account C and C++ ABI, but not
the Swift ABI. Therefore, Swift ABI can only encode information about a C or C++
type that the C and C++ ABI already encodes in order to remain compatible with
future versions of libraries that evolve according to C and C++ ABI
compatibility principles.
The C/C++ compiler does not generate Swift metadata symbols and value witness
tables for C and C++ types. To make a foreign type usable in Swift in the same
way as a native type, the Swift compiler must generate these symbols.
Specifically, each Swift module that uses a given C or C++ type generates the
necessary Swift symbols. For the example above the Swift compiler will generate following
nominal type descriptor symbol for ``CxxStruct`` while compiling the ``main`` module:
.. code::
sSo9CxxStructVMn // -> nominal type descriptor for __C.CxxStruct
Importing C++ class template instantiations
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A class template instantiation is imported as a struct named
``__CxxTemplateInst`` plus Itanium mangled type of the instantiation (see the
``type`` production in the Itanium specification). Note that Itanium mangling is
used on all platforms, regardless of the ABI of the C++ toolchain, to ensure
that the mangled name is a valid Swift type name (this is not the case for MSVC
mangled names). A prefix with a double underscore (to ensure we have a reserved
C++ identifier) is added to limit the possibility for conflicts with names of
user-defined structs. The struct is notionally defined in the ``__C`` module,
similarly to regular C and C++ structs and classes. Consider the following C++
module:
.. code-block:: c++
template<class T>
struct MagicWrapper {
T t;
};
struct MagicNumber {};
typedef MagicWrapper<MagicNumber> WrappedMagicNumber;
``WrappedMagicNumber`` is imported as a typealias for struct
``__CxxTemplateInst12MagicWrapperI11MagicNumberE``. Interface of the imported
module looks as follows:
.. code-block:: swift
struct __CxxTemplateInst12MagicWrapperI11MagicNumberE {
var t: MagicNumber
}
struct MagicNumber {}
typealias WrappedMagicNumber = __CxxTemplateInst12MagicWrapperI11MagicNumberE
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