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proc,dwarf: support string constant parse #4022

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18 changes: 18 additions & 0 deletions pkg/dwarf/godwarf/type.go
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Original file line number Diff line number Diff line change
Expand Up @@ -151,6 +151,12 @@ type BoolType struct {
BasicType
}

// A ConstStringType represents a const string type.
type ConstStringType struct {
BasicType
Value string
}

// An AddrType represents a machine address type.
type AddrType struct {
BasicType
Expand Down Expand Up @@ -1042,6 +1048,18 @@ func readType(d *dwarf.Data, name string, r *dwarf.Reader, off dwarf.Offset, typ
typeCache[off] = t
t.Name, _ = e.Val(dwarf.AttrName).(string)

case dwarf.TagStringType:
// String type (DWARF v3 §5.10)
// Attributes:
// AttrName: name
// AttrType: type of string [used by gdb to determine the size]
// AttrConstValue: value of string
t := new(ConstStringType)
typ = t
typeCache[off] = t
t.Name, _ = e.Val(dwarf.AttrName).(string)
t.Value, _ = e.Val(dwarf.AttrConstValue).(string)

default:
// This is some other type DIE that we're currently not
// equipped to handle. Return an abstract "unsupported type"
Expand Down
29 changes: 19 additions & 10 deletions pkg/proc/bininfo.go
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ import (
"errors"
"fmt"
"go/ast"
"go/constant"
"go/token"
"hash/crc32"
"io"
Expand Down Expand Up @@ -792,7 +793,7 @@ type constantType struct {
type constantValue struct {
name string
fullName string
value int64
value constant.Value
singleBit bool
}

Expand Down Expand Up @@ -2708,17 +2709,25 @@ func (bi *BinaryInfo) loadDebugInfoMapsCompileUnit(ctxt *loadDebugInfoMapsContex
case dwarf.TagConstant:
name, okName := entry.Val(dwarf.AttrName).(string)
typ, okType := entry.Val(dwarf.AttrType).(dwarf.Offset)
val, okVal := entry.Val(dwarf.AttrConstValue).(int64)
if okName && okType && okVal {
if !cu.isgo {
name = "C." + name
if okName && okType {
var cval constant.Value
switch v := entry.Val(dwarf.AttrConstValue).(type) {
case int64:
cval = constant.MakeInt64(v)
case []byte:
cval = constant.MakeString(string(v))
}
ct := bi.consts[dwarfRef{image.index, typ}]
if ct == nil {
ct = &constantType{}
bi.consts[dwarfRef{image.index, typ}] = ct
if cval != nil {
if !cu.isgo {
name = "C." + name
}
ct := bi.consts[dwarfRef{image.index, typ}]
if ct == nil {
ct = &constantType{}
bi.consts[dwarfRef{image.index, typ}] = ct
}
ct.values = append(ct.values, constantValue{name: name, fullName: name, value: cval})
}
ct.values = append(ct.values, constantValue{name: name, fullName: name, value: val})
}
reader.SkipChildren()

Expand Down
15 changes: 13 additions & 2 deletions pkg/proc/eval.go
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Original file line number Diff line number Diff line change
Expand Up @@ -803,9 +803,20 @@ func (scope *EvalScope) findGlobalInternal(name string) (*Variable, error) {
v := newVariable(name, 0x0, t, scope.BinInfo, scope.Mem)
switch v.Kind {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
v.Value = constant.MakeInt64(cval.value)
if n, ok := constant.Int64Val(cval.value); ok {
v.Value = constant.MakeInt64(n)
} else {
return nil, fmt.Errorf("invalid integer constant %s", name)
}
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
v.Value = constant.MakeUint64(uint64(cval.value))
if n, ok := constant.Uint64Val(cval.value); ok {
v.Value = constant.MakeUint64(n)
} else {
return nil, fmt.Errorf("invalid unsigned constant %s", name)
}
case reflect.String:
v.Value = cval.value
v.Len = int64(len(constant.StringVal(cval.value)))
default:
return nil, fmt.Errorf("unsupported constant kind %v", v.Kind)
}
Expand Down
12 changes: 7 additions & 5 deletions pkg/proc/variables.go
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Original file line number Diff line number Diff line change
Expand Up @@ -767,6 +767,8 @@ func newVariable(name string, addr uint64, dwarfType godwarf.Type, bi *BinaryInf
v.Kind = reflect.Invalid
case *godwarf.UnspecifiedType:
v.Kind = reflect.Invalid
case *godwarf.ConstStringType:
v.Kind = reflect.String
default:
v.Unreadable = fmt.Errorf("unknown type: %T", t)
}
Expand Down Expand Up @@ -2307,11 +2309,11 @@ func (cm constantsMap) Get(typ godwarf.Type) *constantType {
if !ctyp.initialized {
ctyp.initialized = true
slices.SortFunc(ctyp.values, func(a, b constantValue) int {
return cmp.Compare(a.value, b.value)
return cmp.Compare(a.value.ExactString(), b.value.ExactString())
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@aarzilli aarzilli Jun 12, 2025

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Numbers shouldn't be sorted as string (nor should we do a conversion to string to sort numbers). I think that storing everything as a constant.Value is probably a mistake, strings and ints should stay in different fields.

})
for i := range ctyp.values {
ctyp.values[i].name = strings.TrimPrefix(ctyp.values[i].name, typepkg)
if bits.OnesCount64(uint64(ctyp.values[i].value)) == 1 {
if v, ok := constant.Int64Val(ctyp.values[i].value); ok && bits.OnesCount64(uint64(v)) == 1 {
ctyp.values[i].singleBit = true
}
}
Expand All @@ -2321,7 +2323,7 @@ func (cm constantsMap) Get(typ godwarf.Type) *constantType {

func (ctyp *constantType) describe(n int64) string {
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@aarzilli aarzilli Jun 12, 2025

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This function should be changed to also handle string constants.

for _, val := range ctyp.values {
if val.value == n {
if v, ok := constant.Int64Val(val.value); ok && v == n {
return val.name
}
}
Expand All @@ -2338,9 +2340,9 @@ func (ctyp *constantType) describe(n int64) string {
if !val.singleBit {
continue
}
if n&val.value != 0 {
if v, ok := constant.Int64Val(val.value); ok && n&v != 0 {
fields = append(fields, val.name)
n = n & ^val.value
n = n & ^v
}
}
if n == 0 {
Expand Down