X need to keep Value first so that sizeof(set-entry) = sizeof(KeyRange)

see github.com/golang/go/issues/48651

wcfs/internal/xbtree/blib/rangemap.go.in

@@ -40,8 +40,8 @@ type RangedMap struct {
 
 // RangedMapEntry represents one entry in RangedMap.
 type RangedMapEntry struct {
-	KeyRange
 	Value    VALUE
+	KeyRange
 }
 
 
@@ -104,7 +104,7 @@ func (M *RangedMap) Get_(k Key) (v VALUE, ok bool) {
 
 // SetRange changes M to map key range r to value v.
 func (M *RangedMap) SetRange(r KeyRange, v VALUE) {
-	e := RangedMapEntry{r,v}
+	e := RangedMapEntry{v,r}
 	if traceRangeMap {
 		fmt.Printf("\n\nSetRange:\n")
 		fmt.Printf("  M: %s\n", M)
@@ -146,8 +146,7 @@ func (M *RangedMap) SetRange(r KeyRange, v VALUE) {
 	if (jhi - ilo) > 1 {
 		lo  := M.entryv[ilo].Lo
 		hi_ := M.entryv[jhi-1].Hi_
-		//vReplaceSlice(&M.entryv, ilo,jhi, KeyRange{lo,hi_})
-		vReplaceSlice(&M.entryv, ilo,jhi, RangedMapEntry{KeyRange{lo,hi_}, v})
+		vReplaceSlice(&M.entryv, ilo,jhi, RangedMapEntry{v, KeyRange{lo,hi_}})
 		debugfRMap("\tmerge M[%d:%d]\t-> %s\n", ilo, jhi, M)
 	}
 	jhi = -1 // no longer valid
@@ -175,7 +174,7 @@ func (M *RangedMap) SetRange(r KeyRange, v VALUE) {
 		right := M.entryv[ilo+1]
 		if (x.Hi_+1 == right.Lo) && (v == right.Value) {
 			vReplaceSlice(&M.entryv, ilo,ilo+2,
-				RangedMapEntry{KeyRange{x.Lo, right.Hi_}, v})
+				RangedMapEntry{v, KeyRange{x.Lo, right.Hi_}})
 			debugfRMap("\tmerge right\t-> %s\n", M)
 		}
 	}
@@ -185,7 +184,7 @@ func (M *RangedMap) SetRange(r KeyRange, v VALUE) {
 		x    := M.entryv[ilo]
 		if (left.Hi_+1 == x.Lo) && (left.Value == v) {
 			vReplaceSlice(&M.entryv, ilo-1,ilo+1,
-				RangedMapEntry{KeyRange{left.Lo, x.Hi_}, v})
+				RangedMapEntry{v, KeyRange{left.Lo, x.Hi_}})
 			debugfRMap("\tmerge left\t-> %s\n", M)
 		}
 	}

wcfs/internal/xbtree/blib/rangeset_test.go

@@ -31,6 +31,9 @@ func TestRangedKeySetTypes(t *testing.T) {
 		t.Errorf("sizeof(void) = %d  ; want 0", sizeVoid)
 	}
 
+	// verify sizeof(set-entry) = sizeof(KeyRange)
+	// NOTE for this to be true Value needs to come first in RangedMapEntry
+	// (see github.com/golang/go/issues/48651)
 	sizeKeyRange := unsafe.Sizeof(KeyRange{})
 	sizeRangedMap_voidEntry := unsafe.Sizeof(_RangedMap_voidEntry{})
 	if sizeRangedMap_voidEntry != sizeKeyRange {
@@ -70,8 +73,8 @@ func TestRangedKeySet(t *testing.T) {
 				hi_--
 			}
 			S.m.entryv = append(S.m.entryv, _RangedMap_voidEntry{
-					KeyRange{lo, hi_},
 					void{},
+					KeyRange{lo, hi_},
 			})
 		}
 		S.verify()

wcfs/internal/xbtree/blib/zrangemap_str.go

@@ -42,8 +42,8 @@ type _RangedMap_str struct {
 
 // _RangedMap_strEntry represents one entry in _RangedMap_str.
 type _RangedMap_strEntry struct {
-	KeyRange
 	Value    string
+	KeyRange
 }
 
 
@@ -106,7 +106,7 @@ func (M *_RangedMap_str) Get_(k Key) (v string, ok bool) {
 
 // SetRange changes M to map key range r to value v.
 func (M *_RangedMap_str) SetRange(r KeyRange, v string) {
-	e := _RangedMap_strEntry{r,v}
+	e := _RangedMap_strEntry{v,r}
 	if trace_RangedMap_str {
 		fmt.Printf("\n\nSetRange:\n")
 		fmt.Printf("  M: %s\n", M)
@@ -148,8 +148,7 @@ func (M *_RangedMap_str) SetRange(r KeyRange, v string) {
 	if (jhi - ilo) > 1 {
 		lo  := M.entryv[ilo].Lo
 		hi_ := M.entryv[jhi-1].Hi_
-		//vReplaceSlice__RangedMap_str(&M.entryv, ilo,jhi, KeyRange{lo,hi_})
-		vReplaceSlice__RangedMap_str(&M.entryv, ilo,jhi, _RangedMap_strEntry{KeyRange{lo,hi_}, v})
+		vReplaceSlice__RangedMap_str(&M.entryv, ilo,jhi, _RangedMap_strEntry{v, KeyRange{lo,hi_}})
 		debugf_RangedMap_str("\tmerge M[%d:%d]\t-> %s\n", ilo, jhi, M)
 	}
 	jhi = -1 // no longer valid
@@ -177,7 +176,7 @@ func (M *_RangedMap_str) SetRange(r KeyRange, v string) {
 		right := M.entryv[ilo+1]
 		if (x.Hi_+1 == right.Lo) && (v == right.Value) {
 			vReplaceSlice__RangedMap_str(&M.entryv, ilo,ilo+2,
-				_RangedMap_strEntry{KeyRange{x.Lo, right.Hi_}, v})
+				_RangedMap_strEntry{v, KeyRange{x.Lo, right.Hi_}})
 			debugf_RangedMap_str("\tmerge right\t-> %s\n", M)
 		}
 	}
@@ -187,7 +186,7 @@ func (M *_RangedMap_str) SetRange(r KeyRange, v string) {
 		x    := M.entryv[ilo]
 		if (left.Hi_+1 == x.Lo) && (left.Value == v) {
 			vReplaceSlice__RangedMap_str(&M.entryv, ilo-1,ilo+1,
-				_RangedMap_strEntry{KeyRange{left.Lo, x.Hi_}, v})
+				_RangedMap_strEntry{v, KeyRange{left.Lo, x.Hi_}})
 			debugf_RangedMap_str("\tmerge left\t-> %s\n", M)
 		}
 	}

wcfs/internal/xbtree/blib/zrangemap_void.go

@@ -42,8 +42,8 @@ type _RangedMap_void struct {
 
 // _RangedMap_voidEntry represents one entry in _RangedMap_void.
 type _RangedMap_voidEntry struct {
-	KeyRange
 	Value    void
+	KeyRange
 }
 
 
@@ -106,7 +106,7 @@ func (M *_RangedMap_void) Get_(k Key) (v void, ok bool) {
 
 // SetRange changes M to map key range r to value v.
 func (M *_RangedMap_void) SetRange(r KeyRange, v void) {
-	e := _RangedMap_voidEntry{r,v}
+	e := _RangedMap_voidEntry{v,r}
 	if trace_RangedMap_void {
 		fmt.Printf("\n\nSetRange:\n")
 		fmt.Printf("  M: %s\n", M)
@@ -148,8 +148,7 @@ func (M *_RangedMap_void) SetRange(r KeyRange, v void) {
 	if (jhi - ilo) > 1 {
 		lo  := M.entryv[ilo].Lo
 		hi_ := M.entryv[jhi-1].Hi_
-		//vReplaceSlice__RangedMap_void(&M.entryv, ilo,jhi, KeyRange{lo,hi_})
-		vReplaceSlice__RangedMap_void(&M.entryv, ilo,jhi, _RangedMap_voidEntry{KeyRange{lo,hi_}, v})
+		vReplaceSlice__RangedMap_void(&M.entryv, ilo,jhi, _RangedMap_voidEntry{v, KeyRange{lo,hi_}})
 		debugf_RangedMap_void("\tmerge M[%d:%d]\t-> %s\n", ilo, jhi, M)
 	}
 	jhi = -1 // no longer valid
@@ -177,7 +176,7 @@ func (M *_RangedMap_void) SetRange(r KeyRange, v void) {
 		right := M.entryv[ilo+1]
 		if (x.Hi_+1 == right.Lo) && (v == right.Value) {
 			vReplaceSlice__RangedMap_void(&M.entryv, ilo,ilo+2,
-				_RangedMap_voidEntry{KeyRange{x.Lo, right.Hi_}, v})
+				_RangedMap_voidEntry{v, KeyRange{x.Lo, right.Hi_}})
 			debugf_RangedMap_void("\tmerge right\t-> %s\n", M)
 		}
 	}
@@ -187,7 +186,7 @@ func (M *_RangedMap_void) SetRange(r KeyRange, v void) {
 		x    := M.entryv[ilo]
 		if (left.Hi_+1 == x.Lo) && (left.Value == v) {
 			vReplaceSlice__RangedMap_void(&M.entryv, ilo-1,ilo+1,
-				_RangedMap_voidEntry{KeyRange{left.Lo, x.Hi_}, v})
+				_RangedMap_voidEntry{v, KeyRange{left.Lo, x.Hi_}})
 			debugf_RangedMap_void("\tmerge left\t-> %s\n", M)
 		}
 	}