const (
// RAX, RBX, RCX, RDI, RSI, R8, R9, R10, R11.
IntArgRegs = 9
// X0 -> X14.
FloatArgRegs = 15
// We use SSE2 registers which support 64-bit float operations.
EffectiveFloatRegSize = 8
)
Map constants common to several packages runtime/runtime-gdb.py:MapTypePrinter contains its own copy
const (
// Maximum number of key/elem pairs a bucket can hold.
MapBucketCountBits = 3 // log2 of number of elements in a bucket.
MapBucketCount = 1 << MapBucketCountBits
// Maximum key or elem size to keep inline (instead of mallocing per element).
// Must fit in a uint8.
// Note: fast map functions cannot handle big elems (bigger than MapMaxElemBytes).
MapMaxKeyBytes = 128
MapMaxElemBytes = 128 // Must fit in a uint8.
)
These constants are shared between the compiler, which uses them for state functions and panic indicators, and the runtime, which turns them into more meaningful strings For best code generation, RF_DONE and RF_READY should be 0 and 1.
const (
RF_DONE = RF_State(iota) // body of loop has exited in a non-panic way
RF_READY // body of loop has not exited yet, is not running -- this is not a panic index
RF_PANIC // body of loop is either currently running, or has panicked
RF_EXHAUSTED // iterator function return, i.e., sequence is "exhausted"
RF_MISSING_PANIC = 4 // body of loop panicked but iterator function defer-recovered it away
)
const (
// StackNosplitBase is the base maximum number of bytes that a chain of
// NOSPLIT functions can use.
//
// This value must be multiplied by the stack guard multiplier, so do not
// use it directly. See runtime/stack.go:stackNosplit and
// cmd/internal/objabi/stack.go:StackNosplit.
StackNosplitBase = 800
// After a stack split check the SP is allowed to be StackSmall bytes below
// the stack guard.
//
// Functions that need frames <= StackSmall can perform the stack check
// using a single comparison directly between the stack guard and the SP
// because we ensure that StackSmall bytes of stack space are available
// beyond the stack guard.
StackSmall = 128
// Functions that need frames <= StackBig can assume that neither
// SP-framesize nor stackGuard-StackSmall will underflow, and thus use a
// more efficient check. In order to ensure this, StackBig must be <= the
// size of the unmapped space at zero.
StackBig = 4096
)
IDs for PCDATA and FUNCDATA tables in Go binaries.
These must agree with ../../../runtime/funcdata.h.
const (
PCDATA_UnsafePoint = 0
PCDATA_StackMapIndex = 1
PCDATA_InlTreeIndex = 2
PCDATA_ArgLiveIndex = 3
FUNCDATA_ArgsPointerMaps = 0
FUNCDATA_LocalsPointerMaps = 1
FUNCDATA_StackObjects = 2
FUNCDATA_InlTree = 3
FUNCDATA_OpenCodedDeferInfo = 4
FUNCDATA_ArgInfo = 5
FUNCDATA_ArgLiveInfo = 6
FUNCDATA_WrapInfo = 7
)
Special values for the PCDATA_UnsafePoint table.
const (
UnsafePointSafe = -1 // Safe for async preemption
UnsafePointUnsafe = -2 // Unsafe for async preemption
// UnsafePointRestart1(2) apply on a sequence of instructions, within
// which if an async preemption happens, we should back off the PC
// to the start of the sequence when resuming.
// We need two so we can distinguish the start/end of the sequence
// in case that two sequences are next to each other.
UnsafePointRestart1 = -3
UnsafePointRestart2 = -4
// Like UnsafePointRestart1, but back to function entry if async preempted.
UnsafePointRestartAtEntry = -5
)
const (
TraceArgsLimit = 10 // print no more than 10 args/components
TraceArgsMaxDepth = 5 // no more than 5 layers of nesting
// maxLen is a (conservative) upper bound of the byte stream length. For
// each arg/component, it has no more than 2 bytes of data (size, offset),
// and no more than one {, }, ... at each level (it cannot have both the
// data and ... unless it is the last one, just be conservative). Plus 1
// for _endSeq.
TraceArgsMaxLen = (TraceArgsMaxDepth*3+2)*TraceArgsLimit + 1
)
Populate the data. The data is a stream of bytes, which contains the offsets and sizes of the non-aggregate arguments or non-aggregate fields/elements of aggregate-typed arguments, along with special "operators". Specifically,
const (
TraceArgsEndSeq = 0xff
TraceArgsStartAgg = 0xfe
TraceArgsEndAgg = 0xfd
TraceArgsDotdotdot = 0xfc
TraceArgsOffsetTooLarge = 0xfb
TraceArgsSpecial = 0xf0 // above this are operators, below this are ordinary offsets
)
ArgsSizeUnknown is set in Func.argsize to mark all functions whose argument size is unknown (C vararg functions, and assembly code without an explicit specification). This value is generated by the compiler, assembler, or linker.
const ArgsSizeUnknown = -0x80000000
const FuncTabBucketSize = 256 * MINFUNC // size of bucket in the pc->func lookup table
const MINFUNC = 16 // minimum size for a function
MaxPtrmaskBytes is the maximum length of a GC ptrmask bitmap, which holds 1-bit entries describing where pointers are in a given type. Above this length, the GC information is recorded as a GC program, which can express repetition compactly. In either form, the information is used by the runtime to initialize the heap bitmap, and for large types (like 128 or more words), they are roughly the same speed. GC programs are never much larger and often more compact. (If large arrays are involved, they can be arbitrarily more compact.)
The cutoff must be large enough that any allocation large enough to use a GC program is large enough that it does not share heap bitmap bytes with any other objects, allowing the GC program execution to assume an aligned start and not use atomic operations. In the current runtime, this means all malloc size classes larger than the cutoff must be multiples of four words. On 32-bit systems that's 16 bytes, and all size classes >= 16 bytes are 16-byte aligned, so no real constraint. On 64-bit systems, that's 32 bytes, and 32-byte alignment is guaranteed for size classes >= 256 bytes. On a 64-bit system, 256 bytes allocated is 32 pointers, the bits for which fit in 4 bytes. So MaxPtrmaskBytes must be >= 4.
We used to use 16 because the GC programs do have some constant overhead to get started, and processing 128 pointers seems to be enough to amortize that overhead well.
To make sure that the runtime's chansend can call typeBitsBulkBarrier, we raised the limit to 2048, so that even 32-bit systems are guaranteed to use bitmaps for objects up to 64 kB in size.
const MaxPtrmaskBytes = 2048
ZeroValSize is the size in bytes of runtime.zeroVal.
const ZeroValSize = 1024
func CommonSize(ptrSize int) int
CommonSize returns sizeof(Type) for a compilation target with a given ptrSize
func Escape[T any](x T) T
Escape forces any pointers in x to escape to the heap.
func FuncPCABI0(f interface{}) uintptr
FuncPCABI0 returns the entry PC of the function f, which must be a direct reference of a function defined as ABI0. Otherwise it is a compile-time error.
Implemented as a compile intrinsic.
func FuncPCABIInternal(f interface{}) uintptr
FuncPCABIInternal returns the entry PC of the function f. If f is a direct reference of a function, it must be defined as ABIInternal. Otherwise it is a compile-time error. If f is not a direct reference of a defined function, it assumes that f is a func value. Otherwise the behavior is undefined.
Implemented as a compile intrinsic.
func ITabTypeOff(ptrSize int) int
ITabTypeOff returns the offset of ITab.Type for a compilation target with a given ptrSize
func NoEscape(p unsafe.Pointer) unsafe.Pointer
NoEscape hides the pointer p from escape analysis, preventing it from escaping to the heap. It compiles down to nothing.
WARNING: This is very subtle to use correctly. The caller must ensure that it's truly safe for p to not escape to the heap by maintaining runtime pointer invariants (for example, that globals and the heap may not generally point into a stack).
func StructFieldSize(ptrSize int) int
StructFieldSize returns sizeof(StructField) for a compilation target with a given ptrSize
func TFlagOff(ptrSize int) int
TFlagOff returns the offset of Type.TFlag for a compilation target with a given ptrSize
func UncommonSize() uint64
UncommonSize returns sizeof(UncommonType). This currently does not depend on ptrSize. This exported function is in an internal package, so it may change to depend on ptrSize in the future.
func UseInterfaceSwitchCache(goarch string) bool
ArrayType represents a fixed array type.
type ArrayType struct {
Type
Elem *Type // array element type
Slice *Type // slice type
Len uintptr
}
type ChanDir int
const (
RecvDir ChanDir = 1 << iota // <-chan
SendDir // chan<-
BothDir = RecvDir | SendDir // chan
InvalidDir ChanDir = 0
)
ChanType represents a channel type
type ChanType struct {
Type
Elem *Type
Dir ChanDir
}
EmptyInterface describes the layout of a "interface{}" or a "any." These are represented differently than non-empty interface, as the first word always points to an abi.Type.
type EmptyInterface struct {
Type *Type
Data unsafe.Pointer
}
A FuncFlag records bits about a function, passed to the runtime.
type FuncFlag uint8
const (
// FuncFlagTopFrame indicates a function that appears at the top of its stack.
// The traceback routine stop at such a function and consider that a
// successful, complete traversal of the stack.
// Examples of TopFrame functions include goexit, which appears
// at the top of a user goroutine stack, and mstart, which appears
// at the top of a system goroutine stack.
FuncFlagTopFrame FuncFlag = 1 << iota
// FuncFlagSPWrite indicates a function that writes an arbitrary value to SP
// (any write other than adding or subtracting a constant amount).
// The traceback routines cannot encode such changes into the
// pcsp tables, so the function traceback cannot safely unwind past
// SPWrite functions. Stopping at an SPWrite function is considered
// to be an incomplete unwinding of the stack. In certain contexts
// (in particular garbage collector stack scans) that is a fatal error.
FuncFlagSPWrite
// FuncFlagAsm indicates that a function was implemented in assembly.
FuncFlagAsm
)
A FuncID identifies particular functions that need to be treated specially by the runtime. Note that in some situations involving plugins, there may be multiple copies of a particular special runtime function.
type FuncID uint8
const (
FuncIDNormal FuncID = iota // not a special function
FuncID_abort
FuncID_asmcgocall
FuncID_asyncPreempt
FuncID_cgocallback
FuncID_corostart
FuncID_debugCallV2
FuncID_gcBgMarkWorker
FuncID_goexit
FuncID_gogo
FuncID_gopanic
FuncID_handleAsyncEvent
FuncID_mcall
FuncID_morestack
FuncID_mstart
FuncID_panicwrap
FuncID_rt0_go
FuncID_runfinq
FuncID_runtime_main
FuncID_sigpanic
FuncID_systemstack
FuncID_systemstack_switch
FuncIDWrapper // any autogenerated code (hash/eq algorithms, method wrappers, etc.)
)
funcType represents a function type.
A *Type for each in and out parameter is stored in an array that directly follows the funcType (and possibly its uncommonType). So a function type with one method, one input, and one output is:
struct {
funcType
uncommonType
[2]*rtype // [0] is in, [1] is out
}
type FuncType struct {
Type
InCount uint16
OutCount uint16 // top bit is set if last input parameter is ...
}
func (t *FuncType) In(i int) *Type
func (t *FuncType) InSlice() []*Type
func (t *FuncType) IsVariadic() bool
func (t *FuncType) NumIn() int
func (t *FuncType) NumOut() int
func (t *FuncType) Out(i int) *Type
func (t *FuncType) OutSlice() []*Type
The first word of every non-empty interface type contains an *ITab. It records the underlying concrete type (Type), the interface type it is implementing (Inter), and some ancillary information.
allocated in non-garbage-collected memory
type ITab struct {
Inter *InterfaceType
Type *Type
Hash uint32 // copy of Type.Hash. Used for type switches.
Fun [1]uintptr // variable sized. fun[0]==0 means Type does not implement Inter.
}
Imethod represents a method on an interface type
type Imethod struct {
Name NameOff // name of method
Typ TypeOff // .(*FuncType) underneath
}
IntArgRegBitmap is a bitmap large enough to hold one bit per integer argument/return register.
type IntArgRegBitmap [(IntArgRegs + 7) / 8]uint8
func (b *IntArgRegBitmap) Get(i int) bool
Get returns whether the i'th bit of the bitmap is set.
nosplit because it's called in extremely sensitive contexts, like on the reflectcall return path.
func (b *IntArgRegBitmap) Set(i int)
Set sets the i'th bit of the bitmap to 1.
type InterfaceSwitch struct {
Cache *InterfaceSwitchCache
NCases int
// Array of NCases elements.
// Each case must be a non-empty interface type.
Cases [1]*InterfaceType
}
type InterfaceSwitchCache struct {
Mask uintptr // mask for index. Must be a power of 2 minus 1
Entries [1]InterfaceSwitchCacheEntry // Mask+1 entries total
}
type InterfaceSwitchCacheEntry struct {
// type of source value (a *Type)
Typ uintptr
// case # to dispatch to
Case int
// itab to use for resulting case variable (a *runtime.itab)
Itab uintptr
}
type InterfaceType struct {
Type
PkgPath Name // import path
Methods []Imethod // sorted by hash
}
func (t *InterfaceType) NumMethod() int
NumMethod returns the number of interface methods in the type's method set.
A Kind represents the specific kind of type that a Type represents. The zero Kind is not a valid kind.
type Kind uint8
const (
Invalid Kind = iota
Bool
Int
Int8
Int16
Int32
Int64
Uint
Uint8
Uint16
Uint32
Uint64
Uintptr
Float32
Float64
Complex64
Complex128
Array
Chan
Func
Interface
Map
Pointer
Slice
String
Struct
UnsafePointer
)
const (
// TODO (khr, drchase) why aren't these in TFlag? Investigate, fix if possible.
KindDirectIface Kind = 1 << 5
KindGCProg Kind = 1 << 6 // Type.gc points to GC program
KindMask Kind = (1 << 5) - 1
)
func (k Kind) String() string
String returns the name of k.
type MapType struct {
Type
Key *Type
Elem *Type
Bucket *Type // internal type representing a hash bucket
// function for hashing keys (ptr to key, seed) -> hash
Hasher func(unsafe.Pointer, uintptr) uintptr
KeySize uint8 // size of key slot
ValueSize uint8 // size of elem slot
BucketSize uint16 // size of bucket
Flags uint32
}
func (mt *MapType) HashMightPanic() bool
func (mt *MapType) IndirectElem() bool
func (mt *MapType) IndirectKey() bool
Note: flag values must match those used in the TMAP case in ../cmd/compile/internal/reflectdata/reflect.go:writeType.
func (mt *MapType) NeedKeyUpdate() bool
func (mt *MapType) ReflexiveKey() bool
Method on non-interface type
type Method struct {
Name NameOff // name of method
Mtyp TypeOff // method type (without receiver)
Ifn TextOff // fn used in interface call (one-word receiver)
Tfn TextOff // fn used for normal method call
}
type Name struct {
Bytes *byte
}
func NewName(n, tag string, exported, embedded bool) Name
func (n Name) Data(off int) *byte
Data does pointer arithmetic on n's Bytes, and that arithmetic is asserted to be safe because the runtime made the call (other packages use DataChecked)
func (n Name) DataChecked(off int, whySafe string) *byte
DataChecked does pointer arithmetic on n's Bytes, and that arithmetic is asserted to be safe for the reason in whySafe (which can appear in a backtrace, etc.)
func (n Name) HasTag() bool
HasTag returns true iff there is tag data following this name
func (n Name) IsBlank() bool
IsBlank indicates whether n is "_".
func (n Name) IsEmbedded() bool
IsEmbedded returns true iff n is embedded (an anonymous field).
func (n Name) IsExported() bool
IsExported returns "is n exported?"
func (n Name) Name() string
Name returns the tag string for n, or empty if there is none.
func (n Name) ReadVarint(off int) (int, int)
ReadVarint parses a varint as encoded by encoding/binary. It returns the number of encoded bytes and the encoded value.
func (n Name) Tag() string
Tag returns the tag string for n, or empty if there is none.
NameOff is the offset to a name from moduledata.types. See resolveNameOff in runtime.
type NameOff int32
type PtrType struct {
Type
Elem *Type // pointer element (pointed at) type
}
type RF_State int
RegArgs is a struct that has space for each argument and return value register on the current architecture.
Assembly code knows the layout of the first two fields of RegArgs.
RegArgs also contains additional space to hold pointers when it may not be safe to keep them only in the integer register space otherwise.
type RegArgs struct {
// Values in these slots should be precisely the bit-by-bit
// representation of how they would appear in a register.
//
// This means that on big endian arches, integer values should
// be in the top bits of the slot. Floats are usually just
// directly represented, but some architectures treat narrow
// width floating point values specially (e.g. they're promoted
// first, or they need to be NaN-boxed).
Ints [IntArgRegs]uintptr // untyped integer registers
Floats [FloatArgRegs]uint64 // untyped float registers
// Ptrs is a space that duplicates Ints but with pointer type,
// used to make pointers passed or returned in registers
// visible to the GC by making the type unsafe.Pointer.
Ptrs [IntArgRegs]unsafe.Pointer
// ReturnIsPtr is a bitmap that indicates which registers
// contain or will contain pointers on the return path from
// a reflectcall. The i'th bit indicates whether the i'th
// register contains or will contain a valid Go pointer.
ReturnIsPtr IntArgRegBitmap
}
func (r *RegArgs) Dump()
func (r *RegArgs) IntRegArgAddr(reg int, argSize uintptr) unsafe.Pointer
IntRegArgAddr returns a pointer inside of r.Ints[reg] that is appropriately offset for an argument of size argSize.
argSize must be non-zero, fit in a register, and a power-of-two.
This method is a helper for dealing with the endianness of different CPU architectures, since sub-word-sized arguments in big endian architectures need to be "aligned" to the upper edge of the register to be interpreted by the CPU correctly.
type SliceType struct {
Type
Elem *Type // slice element type
}
type StructField struct {
Name Name // name is always non-empty
Typ *Type // type of field
Offset uintptr // byte offset of field
}
func (f *StructField) Embedded() bool
type StructType struct {
Type
PkgPath Name
Fields []StructField
}
TFlag is used by a Type to signal what extra type information is available in the memory directly following the Type value.
type TFlag uint8
const (
// TFlagUncommon means that there is a data with a type, UncommonType,
// just beyond the shared-per-type common data. That is, the data
// for struct types will store their UncommonType at one offset, the
// data for interface types will store their UncommonType at a different
// offset. UncommonType is always accessed via a pointer that is computed
// using trust-us-we-are-the-implementors pointer arithmetic.
//
// For example, if t.Kind() == Struct and t.tflag&TFlagUncommon != 0,
// then t has UncommonType data and it can be accessed as:
//
// type structTypeUncommon struct {
// structType
// u UncommonType
// }
// u := &(*structTypeUncommon)(unsafe.Pointer(t)).u
TFlagUncommon TFlag = 1 << 0
// TFlagExtraStar means the name in the str field has an
// extraneous '*' prefix. This is because for most types T in
// a program, the type *T also exists and reusing the str data
// saves binary size.
TFlagExtraStar TFlag = 1 << 1
// TFlagNamed means the type has a name.
TFlagNamed TFlag = 1 << 2
// TFlagRegularMemory means that equal and hash functions can treat
// this type as a single region of t.size bytes.
TFlagRegularMemory TFlag = 1 << 3
// TFlagUnrolledBitmap marks special types that are unrolled-bitmap
// versions of types with GC programs.
// These types need to be deallocated when the underlying object
// is freed.
TFlagUnrolledBitmap TFlag = 1 << 4
)
TextOff is an offset from the top of a text section. See (rtype).textOff in runtime.
type TextOff int32
Type is the runtime representation of a Go type.
Be careful about accessing this type at build time, as the version of this type in the compiler/linker may not have the same layout as the version in the target binary, due to pointer width differences and any experiments. Use cmd/compile/internal/rttype or the functions in compiletype.go to access this type instead. (TODO: this admonition applies to every type in this package. Put it in some shared location?)
type Type struct {
Size_ uintptr
PtrBytes uintptr // number of (prefix) bytes in the type that can contain pointers
Hash uint32 // hash of type; avoids computation in hash tables
TFlag TFlag // extra type information flags
Align_ uint8 // alignment of variable with this type
FieldAlign_ uint8 // alignment of struct field with this type
Kind_ Kind // enumeration for C
// function for comparing objects of this type
// (ptr to object A, ptr to object B) -> ==?
Equal func(unsafe.Pointer, unsafe.Pointer) bool
// GCData stores the GC type data for the garbage collector.
// If the KindGCProg bit is set in kind, GCData is a GC program.
// Otherwise it is a ptrmask bitmap. See mbitmap.go for details.
GCData *byte
Str NameOff // string form
PtrToThis TypeOff // type for pointer to this type, may be zero
}
func TypeFor[T any]() *Type
TypeFor returns the abi.Type for a type parameter.
func TypeOf(a any) *Type
TypeOf returns the abi.Type of some value.
func (t *Type) Align() int
Align returns the alignment of data with type t.
func (t *Type) ArrayType() *ArrayType
ArrayType returns t cast to a *ArrayType, or nil if its tag does not match.
func (t *Type) ChanDir() ChanDir
ChanDir returns the direction of t if t is a channel type, otherwise InvalidDir (0).
func (t *Type) Common() *Type
func (t *Type) Elem() *Type
Elem returns the element type for t if t is an array, channel, map, pointer, or slice, otherwise nil.
func (t *Type) ExportedMethods() []Method
func (t *Type) FieldAlign() int
func (t *Type) FuncType() *FuncType
FuncType returns t cast to a *FuncType, or nil if its tag does not match.
func (t *Type) GcSlice(begin, end uintptr) []byte
func (t *Type) HasName() bool
func (t *Type) IfaceIndir() bool
IfaceIndir reports whether t is stored indirectly in an interface value.
func (t *Type) InterfaceType() *InterfaceType
InterfaceType returns t cast to a *InterfaceType, or nil if its tag does not match.
func (t *Type) IsDirectIface() bool
isDirectIface reports whether t is stored directly in an interface value.
func (t *Type) Key() *Type
func (t *Type) Kind() Kind
func (t *Type) Len() int
Len returns the length of t if t is an array type, otherwise 0
func (t *Type) MapType() *MapType
MapType returns t cast to a *MapType, or nil if its tag does not match.
func (t *Type) NumMethod() int
func (t *Type) Pointers() bool
Pointers reports whether t contains pointers.
func (t *Type) Size() uintptr
Size returns the size of data with type t.
func (t *Type) StructType() *StructType
StructType returns t cast to a *StructType, or nil if its tag does not match.
func (t *Type) Uncommon() *UncommonType
Uncommon returns a pointer to T's "uncommon" data if there is any, otherwise nil
type TypeAssert struct {
Cache *TypeAssertCache
Inter *InterfaceType
CanFail bool
}
type TypeAssertCache struct {
Mask uintptr
Entries [1]TypeAssertCacheEntry
}
type TypeAssertCacheEntry struct {
// type of source value (a *runtime._type)
Typ uintptr
// itab to use for result (a *runtime.itab)
// nil if CanFail is set and conversion would fail.
Itab uintptr
}
TypeOff is the offset to a type from moduledata.types. See resolveTypeOff in runtime.
type TypeOff int32
UncommonType is present only for defined types or types with methods (if T is a defined type, the uncommonTypes for T and *T have methods). Using a pointer to this struct reduces the overall size required to describe a non-defined type with no methods.
type UncommonType struct {
PkgPath NameOff // import path; empty for built-in types like int, string
Mcount uint16 // number of methods
Xcount uint16 // number of exported methods
Moff uint32 // offset from this uncommontype to [mcount]Method
// contains filtered or unexported fields
}
func (t *UncommonType) ExportedMethods() []Method
func (t *UncommonType) Methods() []Method