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

5 files changed, 24 insertions, 2 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
diff --git a/src/pkg/runtime/hashmap.h b/src/pkg/runtime/hashmap.h
index 40dac6e9bd..0737535b55 100644
--- a/src/pkg/runtime/hashmap.h
+++ b/src/pkg/runtime/hashmap.h
@@ -64,7 +64,6 @@
  */
 
 #define	malloc		runtime·mal
-#define	offsetof(s,m)	(uint32)(&(((s*)0)->m))
 #define	memset(a,b,c)	runtime·memclr((byte*)(a), (uint32)(c))
 #define	memcpy(a,b,c)	runtime·mcpy((byte*)(a),(byte*)(b),(uint32)(c))
 #define	assert(a)	if(!(a)) runtime·throw("assert")
diff --git a/src/pkg/runtime/malloc.goc b/src/pkg/runtime/malloc.goc
index 405b05ee96..f5ca9f9183 100644
--- a/src/pkg/runtime/malloc.goc
+++ b/src/pkg/runtime/malloc.goc
@@ -244,6 +244,8 @@ runtime·allocmcache(void)
 	return c;
 }
 
+int32 runtime·sizeof_C_MStats = sizeof(MStats);
+
 void
 runtime·mallocinit(void)
 {
diff --git a/src/pkg/runtime/runtime.c b/src/pkg/runtime/runtime.c
index f2b6c587e9..a2e31d806f 100644
--- a/src/pkg/runtime/runtime.c
+++ b/src/pkg/runtime/runtime.c
@@ -258,6 +258,13 @@ runtime·check(void)
 	float64 j;
 	void* k;
 	uint16* l;
+	struct x1 {
+		byte x;
+	};
+	struct y1 {
+		struct x1 x1;
+		byte y;
+	};
 
 	if(sizeof(a) != 1) runtime·throw("bad a");
 	if(sizeof(b) != 1) runtime·throw("bad b");
@@ -271,7 +278,9 @@ runtime·check(void)
 	if(sizeof(j) != 8) runtime·throw("bad j");
 	if(sizeof(k) != sizeof(uintptr)) runtime·throw("bad k");
 	if(sizeof(l) != sizeof(uintptr)) runtime·throw("bad l");
-//	prints(1"check ok\n");
+	if(sizeof(struct x1) != 1) runtime·throw("bad sizeof x1");
+	if(offsetof(struct y1, y) != 1) runtime·throw("bad offsetof y1.y");
+	if(sizeof(struct y1) != 2) runtime·throw("bad sizeof y1");
 
 	uint32 z;
 	z = 1;
diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index b0fa3891e6..37c8103f34 100644
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -306,6 +306,7 @@ enum {
  */
 #define	nelem(x)	(sizeof(x)/sizeof((x)[0]))
 #define	nil		((void*)0)
+#define	offsetof(s,m)	(uint32)(&(((s*)0)->m))
 
 /*
  * known to compiler