From 84fce9832b7d1dfb8d39eb7cb76d689e306c4eed Mon Sep 17 00:00:00 2001 From: Gernot Vormayr Date: Mon, 8 Jul 2019 01:27:10 +0200 Subject: [PATCH] cmd/cgo: fix check for conversion of ptr to struct field According to the documentation "When passing a pointer to a field in a struct, the Go memory in question is the memory occupied by the field, not the entire struct.". checkAddr states that this should also work with type conversions, which is implemented in isType. However, ast.StarExpr must be enclosed in ast.ParenExpr according to the go spec (see example below), which is not considered in the checks. Example: // struct Si { int i; int *p; }; void f(struct I *x) {} import "C" type S { p *int i C.struct_Si } func main() { v := &S{new(int)} C.f((*C.struct_I)(&v.i)) // <- panic } This example will cause cgo to emit a cgoCheck that checks the whole struct S instead of just S.i causing the panic "cgo argument has Go pointer to Go pointer". This patch fixes this situation by adding support for ast.ParenExpr to isType and adds a test, that fails without the fix. Fixes #32970. Change-Id: I15ea28c98f839e9fa708859ed107a2e5f1483133 Reviewed-on: https://go-review.googlesource.com/c/go/+/185098 Run-TryBot: Ian Lance Taylor TryBot-Result: Gobot Gobot Reviewed-by: Ian Lance Taylor --- misc/cgo/errors/ptr_test.go | 9 +++++++++ src/cmd/cgo/gcc.go | 2 ++ 2 files changed, 11 insertions(+) diff --git a/misc/cgo/errors/ptr_test.go b/misc/cgo/errors/ptr_test.go index 522ef2adfd..4a46b6023b 100644 --- a/misc/cgo/errors/ptr_test.go +++ b/misc/cgo/errors/ptr_test.go @@ -423,6 +423,15 @@ var ptrTests = []ptrTest{ body: `t := reflect.StructOf([]reflect.StructField{{Name: "MyInt38", Type: reflect.TypeOf(MyInt38(0)), Anonymous: true}}); v := reflect.New(t).Elem(); v.Interface().(Getter38).Get()`, fail: false, }, + { + // Test that a converted address of a struct field results + // in a check for just that field and not the whole struct. + name: "structfieldcast", + c: `struct S40i { int i; int* p; }; void f40(struct S40i* p) {}`, + support: `type S40 struct { p *int; a C.struct_S40i }`, + body: `s := &S40{p: new(int)}; C.f40((*C.struct_S40i)(&s.a))`, + fail: false, + }, } func TestPointerChecks(t *testing.T) { diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go index d4e8186cab..1bd3e2417c 100644 --- a/src/cmd/cgo/gcc.go +++ b/src/cmd/cgo/gcc.go @@ -1239,6 +1239,8 @@ func (p *Package) isType(t ast.Expr) bool { if strings.HasPrefix(t.Name, "_Ctype_") { return true } + case *ast.ParenExpr: + return p.isType(t.X) case *ast.StarExpr: return p.isType(t.X) case *ast.ArrayType, *ast.StructType, *ast.FuncType, *ast.InterfaceType, -- 2.48.1