cmd/nm: add -sort=size

When printing the size, we often want to sort on that key.
Because it's used when looking for large things, make the
sort go from largest to smallest.

Perfect recreation of CL 45150044, which was lost to some blunder.

R=golang-codereviews, gobot, rsc
CC=golang-codereviews
https://golang.org/cl/48500044

2 files changed, 11 insertions, 2 deletions

diff --git a/src/cmd/nm/doc.go b/src/cmd/nm/doc.go
index f40073f7a2..81662f8721 100644
--- a/src/cmd/nm/doc.go
+++ b/src/cmd/nm/doc.go
@@ -31,8 +31,9 @@
 //		for compatibility with other nm commands
 //	-size
 //		print symbol size in decimal between address and type
-//	-sort {address,name,none}
+//	-sort {address,name,none,size}
 //		sort output in the given order (default name)
+//		size orders from largest to smallest
 //	-type
 //		print symbol type after name
 //
diff --git a/src/cmd/nm/nm.go b/src/cmd/nm/nm.go
index d369a4ab54..fdf6ef673e 100644
--- a/src/cmd/nm/nm.go
+++ b/src/cmd/nm/nm.go
@@ -58,7 +58,7 @@ func main() {
 	flag.Parse()
 
 	switch *sortOrder {
-	case "address", "name", "none":
+	case "address", "name", "none", "size":
 		// ok
 	default:
 		fmt.Fprintf(os.Stderr, "nm: unknown sort order %q\n", *sortOrder)
@@ -135,6 +135,8 @@ HaveSyms:
 		sort.Sort(byAddr(syms))
 	case "name":
 		sort.Sort(byName(syms))
+	case "size":
+		sort.Sort(bySize(syms))
 	}
 
 	w := bufio.NewWriter(os.Stdout)
@@ -170,3 +172,9 @@ type byName []Sym
 func (x byName) Len() int           { return len(x) }
 func (x byName) Swap(i, j int)      { x[i], x[j] = x[j], x[i] }
 func (x byName) Less(i, j int) bool { return x[i].Name < x[j].Name }
+
+type bySize []Sym
+
+func (x bySize) Len() int           { return len(x) }
+func (x bySize) Swap(i, j int)      { x[i], x[j] = x[j], x[i] }
+func (x bySize) Less(i, j int) bool { return x[i].Size > x[j].Size }