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// Copyright 2009 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.
// Debug arguments, set by -d flag.
package base
import (
// Debug holds the parsed debugging configuration values.
var Debug DebugFlags
// DebugFlags defines the debugging configuration values (see var Debug).
// Each struct field is a different value, named for the lower-case of the field name.
// Each field must be an int or string and must have a `help` struct tag.
// The -d option takes a comma-separated list of settings.
// Each setting is name=value; for ints, name is short for name=1.
type DebugFlags struct {
Append int `help:"print information about append compilation"`
Checkptr int `help:"instrument unsafe pointer conversions"`
Closure int `help:"print information about closure compilation"`
DclStack int `help:"run internal dclstack check"`
Defer int `help:"print information about defer compilation"`
DisableNil int `help:"disable nil checks"`
DumpPtrs int `help:"show Node pointers values in dump output"`
DwarfInl int `help:"print information about DWARF inlined function creation"`
Export int `help:"print export data"`
GCProg int `help:"print dump of GC programs"`
InlFuncsWithClosures int `help:"allow functions with closures to be inlined"`
Libfuzzer int `help:"enable coverage instrumentation for libfuzzer"`
LocationLists int `help:"print information about DWARF location list creation"`
Nil int `help:"print information about nil checks"`
NoOpenDefer int `help:"disable open-coded defers"`
PCTab string `help:"print named pc-value table"`
Panic int `help:"show all compiler panics"`
Slice int `help:"print information about slice compilation"`
SoftFloat int `help:"force compiler to emit soft-float code"`
SyncFrames int `help:"how many writer stack frames to include at sync points in unified export data"`
TypeAssert int `help:"print information about type assertion inlining"`
TypecheckInl int `help:"eager typechecking of inline function bodies"`
Unified int `help:"enable unified IR construction"`
UnifiedQuirks int `help:"enable unified IR construction's quirks mode"`
WB int `help:"print information about write barriers"`
ABIWrap int `help:"print information about ABI wrapper generation"`
any bool // set when any of the values have been set
// Any reports whether any of the debug flags have been set.
func (d *DebugFlags) Any() bool { return d.any }
type debugField struct {
name string
help string
val interface{} // *int or *string
var debugTab []debugField
func init() {
v := reflect.ValueOf(&Debug).Elem()
t := v.Type()
for i := 0; i < t.NumField(); i++ {
f := t.Field(i)
if f.Name == "any" {
name := strings.ToLower(f.Name)
help := f.Tag.Get("help")
if help == "" {
panic(fmt.Sprintf("base.Debug.%s is missing help text", f.Name))
ptr := v.Field(i).Addr().Interface()
switch ptr.(type) {
panic(fmt.Sprintf("base.Debug.%s has invalid type %v (must be int or string)", f.Name, f.Type))
case *int, *string:
// ok
debugTab = append(debugTab, debugField{name, help, ptr})
// DebugSSA is called to set a -d ssa/... option.
// If nil, those options are reported as invalid options.
// If DebugSSA returns a non-empty string, that text is reported as a compiler error.
var DebugSSA func(phase, flag string, val int, valString string) string
// parseDebug parses the -d debug string argument.
func parseDebug(debugstr string) {
// parse -d argument
if debugstr == "" {
Debug.any = true
for _, name := range strings.Split(debugstr, ",") {
if name == "" {
// display help about the -d option itself and quit
if name == "help" {
maxLen := len("ssa/help")
for _, t := range debugTab {
if len( > maxLen {
maxLen = len(
for _, t := range debugTab {
fmt.Printf("\t%-*s\t%s\n", maxLen,,
// ssa options have their own help
fmt.Printf("\t%-*s\t%s\n", maxLen, "ssa/help", "print help about SSA debugging")
val, valstring, haveInt := 1, "", true
if i := strings.IndexAny(name, "=:"); i >= 0 {
var err error
name, valstring = name[:i], name[i+1:]
val, err = strconv.Atoi(valstring)
if err != nil {
val, haveInt = 1, false
for _, t := range debugTab {
if != name {
switch vp := t.val.(type) {
case nil:
// Ignore
case *string:
*vp = valstring
case *int:
if !haveInt {
log.Fatalf("invalid debug value %v", name)
*vp = val
panic("bad debugtab type")
continue Split
// special case for ssa for now
if DebugSSA != nil && strings.HasPrefix(name, "ssa/") {
// expect form ssa/phase/flag
// e.g. -d=ssa/generic_cse/time
// _ in phase name also matches space
phase := name[4:]
flag := "debug" // default flag is debug
if i := strings.Index(phase, "/"); i >= 0 {
flag = phase[i+1:]
phase = phase[:i]
err := DebugSSA(phase, flag, val, valstring)
if err != "" {
continue Split
log.Fatalf("unknown debug key -d %s\n", name)
const debugHelpHeader = `usage: -d arg[,arg]* and arg is <key>[=<value>]
<key> is one of:
const debugHelpFooter = `
<value> is key-specific.
Key "checkptr" supports values:
"0": instrumentation disabled
"1": conversions involving unsafe.Pointer are instrumented
"2": conversions to unsafe.Pointer force heap allocation
Key "pctab" supports values:
"pctospadj", "pctofile", "pctoline", "pctoinline", "pctopcdata"