[release-branch.go1.11] cmd/cgo: don't cache bad pointer typedefs

The set of bad pointer typedefs changes as we see more typedefs, so
avoid looking in the cache when we find one.

Updates #29175
Fixes #29272

Change-Id: Idd82289bdd8628d11a983fa5ec96517e3a5bcbf1
Reviewed-on: https://go-review.googlesource.com/c/153597
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
(cherry picked from commit 01e072db5d26c224dfbe7763a5b94ab23c163983)
Reviewed-on: https://go-review.googlesource.com/c/154299
Run-TryBot: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

1 files changed, 14 insertions, 4 deletions

diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index 588b7ed072..c2f089ee39 100644
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -1900,12 +1900,22 @@ func (c *typeConv) FinishType(pos token.Pos) {
 // 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 {
+	// Always recompute bad pointer typedefs, as the set of such
+	// typedefs changes as we see more types.
+	checkCache := true
+	if dtt, ok := dtype.(*dwarf.TypedefType); ok && c.badPointerTypedef(dtt) {
+		checkCache = false
+	}
+
 	key := dtype.String()
-	if t, ok := c.m[key]; ok {
-		if t.Go == nil {
-			fatalf("%s: type conversion loop at %s", lineno(pos), dtype)
+
+	if checkCache {
+		if t, ok := c.m[key]; ok {
+			if t.Go == nil {
+				fatalf("%s: type conversion loop at %s", lineno(pos), dtype)
+			}
+			return t
 		}
-		return t
 	}
 
 	t := new(Type)