[release-branch.go1.12] cmd/cgo: use explicit type for arg with bad pointer typedef

Fixes #30816
Updates #30646

Change-Id: I5b7e986b0588e87b9781cce01445e3c55c06b6fc
Reviewed-on: https://go-review.googlesource.com/c/go/+/165897
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
(cherry picked from commit a6436a56)
Reviewed-on: https://go-review.googlesource.com/c/go/+/167497
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/cgo/gcc.go

@@ -901,7 +901,7 @@ func (p *Package) rewriteCall(f *File, call *Call) (string, bool) {
 		// constants to the parameter type, to avoid a type mismatch.
 		ptype := p.rewriteUnsafe(param.Go)
 
-		if !p.needsPointerCheck(f, param.Go, args[i]) {
+		if !p.needsPointerCheck(f, param.Go, args[i]) || param.BadPointer {
 			if ptype != param.Go {
 				needsUnsafe = true
 			}
@@ -2465,13 +2465,16 @@ func (c *typeConv) Type(dtype dwarf.Type, pos token.Pos) *Type {
 			// Treat this typedef as a uintptr.
 			s := *sub
 			s.Go = c.uintptr
+			s.BadPointer = true
 			sub = &s
 			// Make sure we update any previously computed type.
 			if oldType := typedef[name.Name]; oldType != nil {
 				oldType.Go = sub.Go
+				oldType.BadPointer = true
 			}
 		}
 		t.Go = name
+		t.BadPointer = sub.BadPointer
 		if unionWithPointer[sub.Go] {
 			unionWithPointer[t.Go] = true
 		}
@@ -2481,6 +2484,7 @@ func (c *typeConv) Type(dtype dwarf.Type, pos token.Pos) *Type {
 		if oldType == nil {
 			tt := *t
 			tt.Go = sub.Go
+			tt.BadPointer = sub.BadPointer
 			typedef[name.Name] = &tt
 		}
 

src/cmd/cgo/main.go

@@ -151,6 +151,7 @@ type Type struct {
 	Go         ast.Expr
 	EnumValues map[string]int64
 	Typedef    string
+	BadPointer bool
 }
 
 // A FuncType collects information about a function type in both the C and Go worlds.