diff --git a/misc/cgo/test/issue27340.go b/misc/cgo/test/issue27340.go
new file mode 100644
index 0000000..f8c8a87
--- /dev/null
+++ b/misc/cgo/test/issue27340.go
@@ -0,0 +1,12 @@
+// Copyright 2018 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.
+
+// Failed to resolve typedefs consistently.
+// No runtime test; just make sure it compiles.
+
+package cgotest
+
+import "./issue27340"
+
+var issue27340Var = issue27340.Issue27340GoFunc
diff --git a/misc/cgo/test/issue27340/a.go b/misc/cgo/test/issue27340/a.go
new file mode 100644
index 0000000..f5b120c
--- /dev/null
+++ b/misc/cgo/test/issue27340/a.go
@@ -0,0 +1,42 @@
+// Copyright 2018 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.
+
+// Failed to resolve typedefs consistently.
+// No runtime test; just make sure it compiles.
+// In separate directory to isolate #pragma GCC diagnostic.
+
+package issue27340
+
+// We use the #pragma to avoid a compiler warning about incompatible
+// pointer types, because we generate code passing a struct ptr rather
+// than using the typedef. This warning is expected and does not break
+// a normal build.
+// We can only disable -Wincompatible-pointer-types starting with GCC 5.
+
+// #if __GNU_MAJOR__ >= 5
+//
+// #pragma GCC diagnostic ignored "-Wincompatible-pointer-types"
+//
+// typedef struct {
+// 	int a;
+// } issue27340Struct, *issue27340Ptr;
+//
+// static void issue27340CFunc(issue27340Ptr p) {}
+//
+// #else /* _GNU_MAJOR_ < 5 */
+//
+// typedef struct {
+// 	int a;
+// } issue27340Struct;
+//
+// static issue27340Struct* issue27340Ptr(issue27340Struct* p) { return p; }
+//
+// static void issue27340CFunc(issue27340Struct *p) {}
+// #endif /* _GNU_MAJOR_ < 5 */
+import "C"
+
+func Issue27340GoFunc() {
+	var s C.issue27340Struct
+	C.issue27340CFunc(C.issue27340Ptr(&s))
+}
diff --git a/misc/cgo/test/issue9026/issue9026.go b/misc/cgo/test/issue9026/issue9026.go
index 0af86e6..149c265 100644
--- a/misc/cgo/test/issue9026/issue9026.go
+++ b/misc/cgo/test/issue9026/issue9026.go
@@ -29,7 +29,7 @@
 	// Brittle: the assertion may fail spuriously when the algorithm
 	// changes, but should remain stable otherwise.
 	got := fmt.Sprintf("%T %T", in, opts)
-	want := "issue9026._Ctype_struct___0 *issue9026._Ctype_struct___1"
+	want := "issue9026._Ctype_struct___0 *issue9026._Ctype_struct___0"
 	if got != want {
 		t.Errorf("Non-deterministic type names: got %s, want %s", got, want)
 	}
diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index 8cbe6d3..17a9936 100644
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -170,6 +170,10 @@
 		// Convert C.ulong to C.unsigned long, etc.
 		cref.Name.C = cname(cref.Name.Go)
 	}
+
+	var conv typeConv
+	conv.Init(p.PtrSize, p.IntSize)
+
 	p.loadDefines(f)
 	p.typedefs = map[string]bool{}
 	p.typedefList = nil
@@ -187,7 +191,7 @@
 		}
 		needType := p.guessKinds(f)
 		if len(needType) > 0 {
-			p.loadDWARF(f, needType)
+			p.loadDWARF(f, &conv, needType)
 		}
 
 		// In godefs mode we're OK with the typedefs, which
@@ -482,7 +486,7 @@
 // loadDWARF parses the DWARF debug information generated
 // by gcc to learn the details of the constants, variables, and types
 // being referred to as C.xxx.
-func (p *Package) loadDWARF(f *File, names []*Name) {
+func (p *Package) loadDWARF(f *File, conv *typeConv, names []*Name) {
 	// Extract the types from the DWARF section of an object
 	// from a well-formed C program. Gcc only generates DWARF info
 	// for symbols in the object file, so it is not enough to print the
@@ -589,8 +593,6 @@
 	}
 
 	// Record types and typedef information.
-	var conv typeConv
-	conv.Init(p.PtrSize, p.IntSize)
 	for i, n := range names {
 		if strings.HasSuffix(n.Go, "GetTypeID") && types[i].String() == "func() CFTypeID" {
 			conv.getTypeIDs[n.Go[:len(n.Go)-9]] = true
@@ -2011,10 +2013,10 @@
 // with equivalent memory layout.
 type typeConv struct {
 	// Cache of already-translated or in-progress types.
-	m map[dwarf.Type]*Type
+	m map[string]*Type
 
 	// Map from types to incomplete pointers to those types.
-	ptrs map[dwarf.Type][]*Type
+	ptrs map[string][]*Type
 	// Keys of ptrs in insertion order (deterministic worklist)
 	// ptrKeys contains exactly the keys in ptrs.
 	ptrKeys []dwarf.Type
@@ -2049,8 +2051,8 @@
 func (c *typeConv) Init(ptrSize, intSize int64) {
 	c.ptrSize = ptrSize
 	c.intSize = intSize
-	c.m = make(map[dwarf.Type]*Type)
-	c.ptrs = make(map[dwarf.Type][]*Type)
+	c.m = make(map[string]*Type)
+	c.ptrs = make(map[string][]*Type)
 	c.getTypeIDs = make(map[string]bool)
 	c.bool = c.Ident("bool")
 	c.byte = c.Ident("byte")
@@ -2158,11 +2160,12 @@
 	// Keep looping until they're all done.
 	for len(c.ptrKeys) > 0 {
 		dtype := c.ptrKeys[0]
+		dtypeKey := dtype.String()
 		c.ptrKeys = c.ptrKeys[1:]
-		ptrs := c.ptrs[dtype]
-		delete(c.ptrs, dtype)
+		ptrs := c.ptrs[dtypeKey]
+		delete(c.ptrs, dtypeKey)
 
-		// Note Type might invalidate c.ptrs[dtype].
+		// Note Type might invalidate c.ptrs[dtypeKey].
 		t := c.Type(dtype, pos)
 		for _, ptr := range ptrs {
 			ptr.Go.(*ast.StarExpr).X = t.Go
@@ -2174,7 +2177,8 @@
 // Type returns a *Type with the same memory layout as
 // dtype when used as the type of a variable or a struct field.
 func (c *typeConv) Type(dtype dwarf.Type, pos token.Pos) *Type {
-	if t, ok := c.m[dtype]; ok {
+	key := dtype.String()
+	if t, ok := c.m[key]; ok {
 		if t.Go == nil {
 			fatalf("%s: type conversion loop at %s", lineno(pos), dtype)
 		}
@@ -2185,7 +2189,7 @@
 	t.Size = dtype.Size() // note: wrong for array of pointers, corrected below
 	t.Align = -1
 	t.C = &TypeRepr{Repr: dtype.Common().Name}
-	c.m[dtype] = t
+	c.m[key] = t
 
 	switch dt := dtype.(type) {
 	default:
@@ -2348,10 +2352,11 @@
 		// Placeholder initialization; completed in FinishType.
 		t.Go = &ast.StarExpr{}
 		t.C.Set("<incomplete>*")
-		if _, ok := c.ptrs[dt.Type]; !ok {
+		key := dt.Type.String()
+		if _, ok := c.ptrs[key]; !ok {
 			c.ptrKeys = append(c.ptrKeys, dt.Type)
 		}
-		c.ptrs[dt.Type] = append(c.ptrs[dt.Type], t)
+		c.ptrs[key] = append(c.ptrs[key], t)
 
 	case *dwarf.QualType:
 		t1 := c.Type(dt.Type, pos)