cmd/cgo: fix mangling of enum and union types
Consider this test package:
package p
// enum E { E0 };
// union U { long x; };
// void f(enum E e, union U* up) {}
import "C"
func f() {
C.f(C.enum_E(C.E0), (*C.union_U)(nil))
}
In Go 1.14, cgo translated this to (omitting irrelevant details):
type _Ctype_union_U [8]byte
func f() {
_Cfunc_f(uint32(_Ciconst_E0), (*[8]byte)(nil))
}
func _Cfunc_f(p0 uint32, p1 *[8]byte) (r1 _Ctype_void) { ... }
Notably, _Ctype_union_U was declared as a defined type, but uses were
being rewritten into uses of the underlying type, which matched how
_Cfunc_f was declared.
After CL 230037, cgo started consistently rewriting "C.foo" type
expressions as "_Ctype_foo", which caused it to start emitting:
type _Ctype_enum_E uint32
type _Ctype_union_U [8]byte
func f() {
_Cfunc_f(_Ctype_enum_E(_Ciconst_E0), (*_Ctype_union_U)(nil))
}
// _Cfunc_f unchanged
Of course, this fails to type-check because _Ctype_enum_E and
_Ctype_union_U are defined types.
This CL changes cgo to emit:
type _Ctype_enum_E = uint32
type _Ctype_union_U = [8]byte
// f unchanged since CL 230037
// _Cfunc_f still unchanged
It would probably be better to fix this in (*typeConv).loadType so
that cgo generated code uses the _Ctype_foo aliases too. But as it
wouldn't have any effect on actual compilation, it's not worth the
risk of touching it at this point in the release cycle.
Updates #39537.
Fixes #40494.
Change-Id: I88269660b40aeda80a9a9433777601a781b48ac0
Reviewed-on: https://go-review.googlesource.com/c/go/+/246057
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/misc/cgo/test/test.go b/misc/cgo/test/test.go
index 8c69ad9..35bc3a1 100644
--- a/misc/cgo/test/test.go
+++ b/misc/cgo/test/test.go
@@ -901,6 +901,12 @@
// issue 38649
// Test that #define'd type aliases work.
#define netbsd_gid unsigned int
+
+// issue 40494
+// Inconsistent handling of tagged enum and union types.
+enum Enum40494 { X_40494 };
+union Union40494 { int x; };
+void issue40494(enum Enum40494 e, union Union40494* up) {}
*/
import "C"
@@ -2204,3 +2210,10 @@
// issue 39877
var issue39877 *C.void = nil
+
+// issue 40494
+// No runtime test; just make sure it compiles.
+
+func Issue40494() {
+ C.issue40494(C.enum_Enum40494(C.X_40494), (*C.union_Union40494)(nil))
+}
diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
index 6c22147..4064f0a 100644
--- a/src/cmd/cgo/out.go
+++ b/src/cmd/cgo/out.go
@@ -123,7 +123,9 @@
// Moreover, empty file name makes compile emit no source debug info at all.
var buf bytes.Buffer
noSourceConf.Fprint(&buf, fset, def.Go)
- if bytes.HasPrefix(buf.Bytes(), []byte("_Ctype_")) {
+ if bytes.HasPrefix(buf.Bytes(), []byte("_Ctype_")) ||
+ strings.HasPrefix(name, "_Ctype_enum_") ||
+ strings.HasPrefix(name, "_Ctype_union_") {
// This typedef is of the form `typedef a b` and should be an alias.
fmt.Fprintf(fgo2, "= ")
}
