cmd/cgo: correct padding required by alignment

If the aligned offset isn't sufficient for the field offset,
we were padding based on the aligned offset. We need to pad
based on the original offset instead.

Also set the Go alignment correctly for int128. We were defaulting
to the maximum alignment, but since we translate int128 into an
array of uint8 the correct Go alignment is 1.

Fixes #69086

Change-Id: I23ce583335c81beac2ac51f7f9336ac97ccebf09
Reviewed-on: https://go-review.googlesource.com/c/go/+/608815
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>

diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index 504a5650631cd37e5bd6637e14dc975682637d8c..0f90761e14bf8ce5a5bbb4d760282eb59139d87a 100644 (file)
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -2577,6 +2577,11 @@ func (c *typeConv) loadType(dtype dwarf.Type, pos token.Pos, parent string) *Typ
                if dt.BitSize > 0 {
                        fatalf("%s: unexpected: %d-bit int type - %s", lineno(pos), dt.BitSize, dtype)
                }
+
+               if t.Align = t.Size; t.Align >= c.ptrSize {
+                       t.Align = c.ptrSize
+               }
+
                switch t.Size {
                default:
                        fatalf("%s: unexpected: %d-byte int type - %s", lineno(pos), t.Size, dtype)
@@ -2593,9 +2598,8 @@ func (c *typeConv) loadType(dtype dwarf.Type, pos token.Pos, parent string) *Typ
                                Len: c.intExpr(t.Size),
                                Elt: c.uint8,
                        }
-               }
-               if t.Align = t.Size; t.Align >= c.ptrSize {
-                       t.Align = c.ptrSize
+                       // t.Align is the alignment of the Go type.
+                       t.Align = 1
                }
 
        case *dwarf.PtrType:
@@ -2824,6 +2828,11 @@ func (c *typeConv) loadType(dtype dwarf.Type, pos token.Pos, parent string) *Typ
                if dt.BitSize > 0 {
                        fatalf("%s: unexpected: %d-bit uint type - %s", lineno(pos), dt.BitSize, dtype)
                }
+
+               if t.Align = t.Size; t.Align >= c.ptrSize {
+                       t.Align = c.ptrSize
+               }
+
                switch t.Size {
                default:
                        fatalf("%s: unexpected: %d-byte uint type - %s", lineno(pos), t.Size, dtype)
@@ -2840,9 +2849,8 @@ func (c *typeConv) loadType(dtype dwarf.Type, pos token.Pos, parent string) *Typ
                                Len: c.intExpr(t.Size),
                                Elt: c.uint8,
                        }
-               }
-               if t.Align = t.Size; t.Align >= c.ptrSize {
-                       t.Align = c.ptrSize
+                       // t.Align is the alignment of the Go type.
+                       t.Align = 1
                }
 
        case *dwarf.VoidType:
@@ -3108,10 +3116,11 @@ func (c *typeConv) Struct(dt *dwarf.StructType, pos token.Pos) (expr *ast.Struct
                }
 
                // Round off up to talign, assumed to be a power of 2.
+               origOff := off
                off = (off + talign - 1) &^ (talign - 1)
 
                if f.ByteOffset > off {
-                       fld, sizes = c.pad(fld, sizes, f.ByteOffset-off)
+                       fld, sizes = c.pad(fld, sizes, f.ByteOffset-origOff)
                        off = f.ByteOffset
                }
                if f.ByteOffset < off {

diff --git a/src/cmd/cgo/internal/test/cgo_test.go b/src/cmd/cgo/internal/test/cgo_test.go
index 5e02888b3dddd9cb185998ed61ca6ea2c28b445c..5393552e07a4d1130267f1bdc19627a51060cb3f 100644 (file)
--- a/src/cmd/cgo/internal/test/cgo_test.go
+++ b/src/cmd/cgo/internal/test/cgo_test.go
@@ -70,6 +70,7 @@ func Test31891(t *testing.T)                 { test31891(t) }
 func Test42018(t *testing.T)                 { test42018(t) }
 func Test45451(t *testing.T)                 { test45451(t) }
 func Test49633(t *testing.T)                 { test49633(t) }
+func Test69086(t *testing.T)                 { test69086(t) }
 func TestAlign(t *testing.T)                 { testAlign(t) }
 func TestAtol(t *testing.T)                  { testAtol(t) }
 func TestBlocking(t *testing.T)              { testBlocking(t) }

diff --git a/src/cmd/cgo/internal/test/test.go b/src/cmd/cgo/internal/test/test.go
index 34a812ed22c699a7cacb20557b2dab68527bc066..c1375c2691a13115e5c2472d8551c5a39dd6da7c 100644 (file)
--- a/src/cmd/cgo/internal/test/test.go
+++ b/src/cmd/cgo/internal/test/test.go
@@ -940,6 +940,19 @@ typedef struct {
 } issue67517struct;
 static void issue67517(issue67517struct* p) {}
 
+// Issue 69086.
+// GCC added the __int128 type in GCC 4.6, released in 2011.
+typedef struct {
+       int a;
+#ifdef __SIZEOF_INT128__
+       unsigned __int128 b;
+#else
+       uint64_t b;
+#endif
+       unsigned char c;
+} issue69086struct;
+static int issue690861(issue69086struct* p) { p->b = 1234; return p->c; }
+static int issue690862(unsigned long ul1, unsigned long ul2, unsigned int u, issue69086struct s) { return (int)(s.b); }
 */
 import "C"
 
@@ -2349,3 +2362,24 @@ func issue67517() {
                b: nil,
        })
 }
+
+// Issue 69086.
+func test69086(t *testing.T) {
+       var s C.issue69086struct
+
+       typ := reflect.TypeOf(s)
+       for i := 0; i < typ.NumField(); i++ {
+               f := typ.Field(i)
+               t.Logf("field %d: name %s size %d align %d offset %d", i, f.Name, f.Type.Size(), f.Type.Align(), f.Offset)
+       }
+
+       s.c = 1
+       got := C.issue690861(&s)
+       if got != 1 {
+               t.Errorf("field: got %d, want 1", got)
+       }
+       got = C.issue690862(1, 2, 3, s)
+       if got != 1234 {
+               t.Errorf("call: got %d, want 1234", got)
+       }
+}