gc: align structs according to max alignment of fields

cc: same
runtime: test cc alignment (required moving #define of offsetof to runtime.h)
fix bug260

Fixes #482.
Fixes #609.

R=ken2, r
CC=golang-dev
https://golang.org/cl/3563042

1 files changed, 11 insertions, 0 deletions

diff --git a/src/pkg/runtime/debug.go b/src/pkg/runtime/debug.go
index 3cc5472f6b..3ce35cc5ba 100644
--- a/src/pkg/runtime/debug.go
+++ b/src/pkg/runtime/debug.go
@@ -4,6 +4,8 @@
 
 package runtime
 
+import "unsafe"
+
 // Breakpoint() executes a breakpoint trap.
 func Breakpoint()
 
@@ -73,6 +75,15 @@ type MemStatsType struct {
 	}
 }
 
+var sizeof_C_MStats int // filled in by malloc.goc
+
+func init() {
+	if sizeof_C_MStats != unsafe.Sizeof(MemStats) {
+		println(sizeof_C_MStats, unsafe.Sizeof(MemStats))
+		panic("MStats vs MemStatsType size mismatch")
+	}
+}
+
 // MemStats holds statistics about the memory system.
 // The statistics are only approximate, as they are not interlocked on update.
 var MemStats MemStatsType