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error.go
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error.go
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// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package runtime
import "internal/bytealg"
// The Error interface identifies a run time error.
type Error interface {
error
// RuntimeError is a no-op function but
// serves to distinguish types that are run time
// errors from ordinary errors: a type is a
// run time error if it has a RuntimeError method.
RuntimeError()
}
// A TypeAssertionError explains a failed type assertion.
type TypeAssertionError struct {
_interface *_type
concrete *_type
asserted *_type
missingMethod string // one method needed by Interface, missing from Concrete
}
func (*TypeAssertionError) RuntimeError() {}
func (e *TypeAssertionError) Error() string {
inter := "interface"
if e._interface != nil {
inter = e._interface.string()
}
as := e.asserted.string()
if e.concrete == nil {
return "interface conversion: " + inter + " is nil, not " + as
}
cs := e.concrete.string()
if e.missingMethod == "" {
msg := "interface conversion: " + inter + " is " + cs + ", not " + as
if cs == as {
// provide slightly clearer error message
if e.concrete.pkgpath() != e.asserted.pkgpath() {
msg += " (types from different packages)"
} else {
msg += " (types from different scopes)"
}
}
return msg
}
return "interface conversion: " + cs + " is not " + as +
": missing method " + e.missingMethod
}
//go:nosplit
// itoa converts val to a decimal representation. The result is
// written somewhere within buf and the location of the result is returned.
// buf must be at least 20 bytes.
func itoa(buf []byte, val uint64) []byte {
i := len(buf) - 1
for val >= 10 {
buf[i] = byte(val%10 + '0')
i--
val /= 10
}
buf[i] = byte(val + '0')
return buf[i:]
}
// An errorString represents a runtime error described by a single string.
type errorString string
func (e errorString) RuntimeError() {}
func (e errorString) Error() string {
return "runtime error: " + string(e)
}
type errorAddressString struct {
msg string // error message
addr uintptr // memory address where the error occurred
}
func (e errorAddressString) RuntimeError() {}
func (e errorAddressString) Error() string {
return "runtime error: " + e.msg
}
// Addr returns the memory address where a fault occurred.
// The address provided is best-effort.
// The veracity of the result may depend on the platform.
// Errors providing this method will only be returned as
// a result of using runtime/debug.SetPanicOnFault.
func (e errorAddressString) Addr() uintptr {
return e.addr
}
// plainError represents a runtime error described a string without
// the prefix "runtime error: " after invoking errorString.Error().
// See Issue #14965.
type plainError string
func (e plainError) RuntimeError() {}
func (e plainError) Error() string {
return string(e)
}
// A boundsError represents an indexing or slicing operation gone wrong.
type boundsError struct {
x int64
y int
// Values in an index or slice expression can be signed or unsigned.
// That means we'd need 65 bits to encode all possible indexes, from -2^63 to 2^64-1.
// Instead, we keep track of whether x should be interpreted as signed or unsigned.
// y is known to be nonnegative and to fit in an int.
signed bool
code boundsErrorCode
}
type boundsErrorCode uint8
const (
boundsIndex boundsErrorCode = iota // s[x], 0 <= x < len(s) failed
boundsSliceAlen // s[?:x], 0 <= x <= len(s) failed
boundsSliceAcap // s[?:x], 0 <= x <= cap(s) failed
boundsSliceB // s[x:y], 0 <= x <= y failed (but boundsSliceA didn't happen)
boundsSlice3Alen // s[?:?:x], 0 <= x <= len(s) failed
boundsSlice3Acap // s[?:?:x], 0 <= x <= cap(s) failed
boundsSlice3B // s[?:x:y], 0 <= x <= y failed (but boundsSlice3A didn't happen)
boundsSlice3C // s[x:y:?], 0 <= x <= y failed (but boundsSlice3A/B didn't happen)
// Note: in the above, len(s) and cap(s) are stored in y
)
// boundsErrorFmts provide error text for various out-of-bounds panics.
// Note: if you change these strings, you should adjust the size of the buffer
// in boundsError.Error below as well.
var boundsErrorFmts = [...]string{
boundsIndex: "index out of range [%x] with length %y",
boundsSliceAlen: "slice bounds out of range [:%x] with length %y",
boundsSliceAcap: "slice bounds out of range [:%x] with capacity %y",
boundsSliceB: "slice bounds out of range [%x:%y]",
boundsSlice3Alen: "slice bounds out of range [::%x] with length %y",
boundsSlice3Acap: "slice bounds out of range [::%x] with capacity %y",
boundsSlice3B: "slice bounds out of range [:%x:%y]",
boundsSlice3C: "slice bounds out of range [%x:%y:]",
}
// boundsNegErrorFmts are overriding formats if x is negative. In this case there's no need to report y.
var boundsNegErrorFmts = [...]string{
boundsIndex: "index out of range [%x]",
boundsSliceAlen: "slice bounds out of range [:%x]",
boundsSliceAcap: "slice bounds out of range [:%x]",
boundsSliceB: "slice bounds out of range [%x:]",
boundsSlice3Alen: "slice bounds out of range [::%x]",
boundsSlice3Acap: "slice bounds out of range [::%x]",
boundsSlice3B: "slice bounds out of range [:%x:]",
boundsSlice3C: "slice bounds out of range [%x::]",
}
func (e boundsError) RuntimeError() {}
func appendIntStr(b []byte, v int64, signed bool) []byte {
if signed && v < 0 {
b = append(b, '-')
v = -v
}
var buf [20]byte
b = append(b, itoa(buf[:], uint64(v))...)
return b
}
func (e boundsError) Error() string {
fmt := boundsErrorFmts[e.code]
if e.signed && e.x < 0 {
fmt = boundsNegErrorFmts[e.code]
}
// max message length is 99: "runtime error: slice bounds out of range [::%x] with capacity %y"
// x can be at most 20 characters. y can be at most 19.
b := make([]byte, 0, 100)
b = append(b, "runtime error: "...)
for i := 0; i < len(fmt); i++ {
c := fmt[i]
if c != '%' {
b = append(b, c)
continue
}
i++
switch fmt[i] {
case 'x':
b = appendIntStr(b, e.x, e.signed)
case 'y':
b = appendIntStr(b, int64(e.y), true)
}
}
return string(b)
}
type stringer interface {
String() string
}
// printany prints an argument passed to panic.
// If panic is called with a value that has a String or Error method,
// it has already been converted into a string by preprintpanics.
func printany(i interface{}) {
switch v := i.(type) {
case nil:
print("nil")
case bool:
print(v)
case int:
print(v)
case int8:
print(v)
case int16:
print(v)
case int32:
print(v)
case int64:
print(v)
case uint:
print(v)
case uint8:
print(v)
case uint16:
print(v)
case uint32:
print(v)
case uint64:
print(v)
case uintptr:
print(v)
case float32:
print(v)
case float64:
print(v)
case complex64:
print(v)
case complex128:
print(v)
case string:
print(v)
default:
printanycustomtype(i)
}
}
func printanycustomtype(i interface{}) {
eface := efaceOf(&i)
typestring := eface._type.string()
switch eface._type.kind {
case kindString:
print(typestring, `("`, *(*string)(eface.data), `")`)
case kindBool:
print(typestring, "(", *(*bool)(eface.data), ")")
case kindInt:
print(typestring, "(", *(*int)(eface.data), ")")
case kindInt8:
print(typestring, "(", *(*int8)(eface.data), ")")
case kindInt16:
print(typestring, "(", *(*int16)(eface.data), ")")
case kindInt32:
print(typestring, "(", *(*int32)(eface.data), ")")
case kindInt64:
print(typestring, "(", *(*int64)(eface.data), ")")
case kindUint:
print(typestring, "(", *(*uint)(eface.data), ")")
case kindUint8:
print(typestring, "(", *(*uint8)(eface.data), ")")
case kindUint16:
print(typestring, "(", *(*uint16)(eface.data), ")")
case kindUint32:
print(typestring, "(", *(*uint32)(eface.data), ")")
case kindUint64:
print(typestring, "(", *(*uint64)(eface.data), ")")
case kindUintptr:
print(typestring, "(", *(*uintptr)(eface.data), ")")
case kindFloat32:
print(typestring, "(", *(*float32)(eface.data), ")")
case kindFloat64:
print(typestring, "(", *(*float64)(eface.data), ")")
case kindComplex64:
print(typestring, *(*complex64)(eface.data))
case kindComplex128:
print(typestring, *(*complex128)(eface.data))
default:
print("(", typestring, ") ", eface.data)
}
}
// panicwrap generates a panic for a call to a wrapped value method
// with a nil pointer receiver.
//
// It is called from the generated wrapper code.
func panicwrap() {
pc := getcallerpc()
name := funcname(findfunc(pc))
// name is something like "main.(*T).F".
// We want to extract pkg ("main"), typ ("T"), and meth ("F").
// Do it by finding the parens.
i := bytealg.IndexByteString(name, '(')
if i < 0 {
throw("panicwrap: no ( in " + name)
}
pkg := name[:i-1]
if i+2 >= len(name) || name[i-1:i+2] != ".(*" {
throw("panicwrap: unexpected string after package name: " + name)
}
name = name[i+2:]
i = bytealg.IndexByteString(name, ')')
if i < 0 {
throw("panicwrap: no ) in " + name)
}
if i+2 >= len(name) || name[i:i+2] != ")." {
throw("panicwrap: unexpected string after type name: " + name)
}
typ := name[:i]
meth := name[i+2:]
panic(plainError("value method " + pkg + "." + typ + "." + meth + " called using nil *" + typ + " pointer"))
}