invalid entry tag, only supports FormalParameter and Variabl

Error message

invalid entry tag, only supports FormalParameter and Variable, got %s

What it means

`extractVarInfoFromEntry` only knows how to materialize variables from DWARF DIEs whose tag is `DW_TAG_formal_parameter` or `DW_TAG_variable`. Any other DIE tag (e.g. DW_TAG_member, DW_TAG_constant, DW_TAG_typedef) passed to it produces this error. It is an internal invariant check used mainly when extracting function arguments/locals (e.g. for breakpoint argument extraction).

Source

Thrown at pkg/proc/variables.go:1231

func readVarEntry(entry *godwarf.Tree, image *Image) (name string, typ godwarf.Type, err error) {
	name, ok := entry.Val(dwarf.AttrName).(string)
	if !ok {
		return "", nil, errors.New("malformed variable DIE (name)")
	}

	typ, err = entry.Type(image.dwarf, image.index, image.typeCache)
	if err != nil {
		return "", nil, err
	}

	return name, typ, nil
}

// Extracts the name and type of a variable from a dwarf entry
// then executes the instructions given in the  DW_AT_location attribute to grab the variable's address
func extractVarInfoFromEntry(tgt *Target, bi *BinaryInfo, image *Image, regs op.DwarfRegisters, mem MemoryReadWriter, entry *godwarf.Tree, dictAddr uint64) (*Variable, error) {
	if entry.Tag != dwarf.TagFormalParameter && entry.Tag != dwarf.TagVariable {
		return nil, fmt.Errorf("invalid entry tag, only supports FormalParameter and Variable, got %s", entry.Tag.String())
	}

	n, t, err := readVarEntry(entry, image)
	if err != nil {
		return nil, err
	}

	t, err = resolveParametricType(bi, mem, t, dictAddr)
	if err != nil {
		// Log the error, keep going with t, which will be the shape type
		logflags.DebuggerLogger().Errorf("could not resolve parametric type of %s: %v", n, err)
	}

	addr, pieces, descr, err := bi.Location(entry, dwarf.AttrLocation, regs.PC(), regs, mem)
	if pieces != nil {
		var cmem *compositeMemory
		if tgt != nil {
			addr, cmem, err = tgt.newCompositeMemory(mem, regs, pieces, descr, t.Common().ByteSize)

View on GitHub (pinned to a23773e6c3)

Solutions

Filter the DIE tree before extraction to only entries with dwarf.TagFormalParameter or dwarf.TagVariable.
Rebuild the debugged binary with the standard Go toolchain so DWARF has the expected structure.
If using delve as a library, skip unsupported tags instead of passing them to extractVarInfoFromEntry.

Example fix

// before
for _, child := range fnTree.Children {
    v, err := extractVarInfoFromEntry(tgt, bi, image, regs, mem, child, dictAddr)
    ...
}
// after
for _, child := range fnTree.Children {
    if child.Tag != dwarf.TagFormalParameter && child.Tag != dwarf.TagVariable {
        continue
    }
    v, err := extractVarInfoFromEntry(tgt, bi, image, regs, mem, child, dictAddr)
    ...
}

Defensive patterns

Strategy: type-guard

Validate before calling

if entry.Tag != dwarf.TagFormalParameter && entry.Tag != dwarf.TagVariable {
    continue // or handle explicitly before calling extractVarInfoFromEntry
}

Type guard

func isVariableLikeTag(t dwarf.Tag) bool {
    return t == dwarf.TagFormalParameter || t == dwarf.TagVariable
}

Try / catch

v, err := extractVarInfoFromEntry(tgt, bi, image, regs, mem, entry, dictAddr)
if err != nil {
    if strings.HasPrefix(err.Error(), "invalid entry tag") {
        // skip non-variable DIE
        return nil, nil
    }
    return nil, err
}

Prevention

Filter DIE children by tag before extraction when walking function trees.
Build debugged binaries with the standard Go toolchain.
When embedding delve as a library, treat unsupported tags as skippable, not fatal.

When it happens

Trigger: Calling internal APIs that enumerate a function's parameter/local DIEs (e.g. function argument extraction at breakpoints, `Function.Arguments`-style flows) when the DIE iterator yields an entry with an unsupported tag; can happen with unusual compiler output or hand-written DWARF.

Common situations: Debugging binaries produced by non-standard toolchains or older/newer Go compilers emitting unexpected DIE tags; custom tooling that reuses delve's `proc` package to walk DIE trees and hits DW_TAG_constant or DW_TAG_member entries.

Related errors

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/9651c3900a794e08. Report an issue: GitHub.