From: Rob Pike <r@golang.org>
Date: Thu, 30 Apr 2009 01:51:12 +0000 (-0700)
Subject: Bug in reflect found by gri.  Structs in 6g have a minimum alignment.
X-Git-Tag: weekly.2009-11-06~1740
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=c0b8b969ae353f48445a18ea9e856f1997fba270;p=gostls13.git

Bug in reflect found by gri.  Structs in 6g have a minimum alignment.
iant: will this be ok in gccgo?

R=rsc
DELTA=9  (8 added, 0 deleted, 1 changed)
OCL=28059
CL=28062
---

diff --git a/src/lib/reflect/type.go b/src/lib/reflect/type.go
index 107fd78779..b073afc22e 100644
--- a/src/lib/reflect/type.go
+++ b/src/lib/reflect/type.go
@@ -80,9 +80,13 @@ type allTypes struct {
 	xuintptr	uintptr;
 }
 
-var x allTypes
+var (
+	x allTypes;
+	minStruct struct { uint8 };
+)
 
 const (
+	minStructAlign = unsafe.Sizeof(minStruct) - 1;
 	ptrsize = unsafe.Sizeof(&x);
 	interfacesize = unsafe.Sizeof(x.xinterface);
 )
@@ -394,6 +398,10 @@ func (t *structTypeStruct) Size() int {
 		size += elemsize;
 	}
 	if (structalign > 0) {
+		// 6g etc. always aligns structs to a minimum size, typically int64
+		if structalign < minStructAlign {
+			structalign = minStructAlign
+		}
 		// TODO: In the PPC64 ELF ABI, floating point fields
 		// in a struct are aligned to a 4-byte boundary, but
 		// if the first field in the struct is a 64-bit float,