1 files changed, 136 insertions, 0 deletions
diff --git a/src/internal/pkgbits/sync.go b/src/internal/pkgbits/sync.go
new file mode 100644
index 0000000..1520b73
--- /dev/null
+++ b/src/internal/pkgbits/sync.go
@@ -0,0 +1,136 @@
+// Copyright 2021 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 pkgbits
+
+import (
+	"fmt"
+	"runtime"
+	"strings"
+)
+
+// fmtFrames formats a backtrace for reporting reader/writer desyncs.
+func fmtFrames(pcs ...uintptr) []string {
+	res := make([]string, 0, len(pcs))
+	walkFrames(pcs, func(file string, line int, name string, offset uintptr) {
+		// Trim package from function name. It's just redundant noise.
+		name = strings.TrimPrefix(name, "cmd/compile/internal/noder.")
+
+		res = append(res, fmt.Sprintf("%s:%v: %s +0x%v", file, line, name, offset))
+	})
+	return res
+}
+
+type frameVisitor func(file string, line int, name string, offset uintptr)
+
+// walkFrames calls visit for each call frame represented by pcs.
+//
+// pcs should be a slice of PCs, as returned by runtime.Callers.
+func walkFrames(pcs []uintptr, visit frameVisitor) {
+	if len(pcs) == 0 {
+		return
+	}
+
+	frames := runtime.CallersFrames(pcs)
+	for {
+		frame, more := frames.Next()
+		visit(frame.File, frame.Line, frame.Function, frame.PC-frame.Entry)
+		if !more {
+			return
+		}
+	}
+}
+
+// SyncMarker is an enum type that represents markers that may be
+// written to export data to ensure the reader and writer stay
+// synchronized.
+type SyncMarker int
+
+//go:generate stringer -type=SyncMarker -trimprefix=Sync
+
+const (
+	_ SyncMarker = iota
+
+	// Public markers (known to go/types importers).
+
+	// Low-level coding markers.
+	SyncEOF
+	SyncBool
+	SyncInt64
+	SyncUint64
+	SyncString
+	SyncValue
+	SyncVal
+	SyncRelocs
+	SyncReloc
+	SyncUseReloc
+
+	// Higher-level object and type markers.
+	SyncPublic
+	SyncPos
+	SyncPosBase
+	SyncObject
+	SyncObject1
+	SyncPkg
+	SyncPkgDef
+	SyncMethod
+	SyncType
+	SyncTypeIdx
+	SyncTypeParamNames
+	SyncSignature
+	SyncParams
+	SyncParam
+	SyncCodeObj
+	SyncSym
+	SyncLocalIdent
+	SyncSelector
+
+	// Private markers (only known to cmd/compile).
+	SyncPrivate
+
+	SyncFuncExt
+	SyncVarExt
+	SyncTypeExt
+	SyncPragma
+
+	SyncExprList
+	SyncExprs
+	SyncExpr
+	SyncExprType
+	SyncAssign
+	SyncOp
+	SyncFuncLit
+	SyncCompLit
+
+	SyncDecl
+	SyncFuncBody
+	SyncOpenScope
+	SyncCloseScope
+	SyncCloseAnotherScope
+	SyncDeclNames
+	SyncDeclName
+
+	SyncStmts
+	SyncBlockStmt
+	SyncIfStmt
+	SyncForStmt
+	SyncSwitchStmt
+	SyncRangeStmt
+	SyncCaseClause
+	SyncCommClause
+	SyncSelectStmt
+	SyncDecls
+	SyncLabeledStmt
+	SyncUseObjLocal
+	SyncAddLocal
+	SyncLinkname
+	SyncStmt1
+	SyncStmtsEnd
+	SyncLabel
+	SyncOptLabel
+
+	SyncMultiExpr
+	SyncRType
+	SyncConvRTTI
+)