Commit a96884cf authored by Brad Fitzpatrick's avatar Brad Fitzpatrick

net/http: use dynamic type assertion to remove HTTP server code from cmd/go

I was wondering why cmd/go includes the HTTP server implementations.

Dumping the linker's deadcode dependency graph into a file and doing
some graph analysis, I found that the only reason cmd/go included an
HTTP server was because the maxBytesReader type (used by both the HTTP
transport & HTTP server) did a static type assertion to an HTTP server
type.

Changing it to a interface type assertion reduces the size of cmd/go
by 533KB (5.2%)

On linux/amd64, cmd/go goes from 10549200 to 10002624 bytes.

Add a test too so this doesn't regress. The test uses cmd/go as the
binary to test (a binary which needs the HTTP client but not the HTTP
server), but this change and test are equally applicable to any such
program.

Change-Id: I93865f43ec03b06d09241fbd9ea381817c2909c5
Reviewed-on: https://go-review.googlesource.com/20763Reviewed-by: default avatarMatthew Dempsky <mdempsky@google.com>
Reviewed-by: default avatarJosh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: default avatarDavid Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
parent bb3b1021
......@@ -2,12 +2,17 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Tests of internal functions with no better homes.
// Tests of internal functions and things with no better homes.
package http
import (
"bytes"
"internal/testenv"
"os/exec"
"path/filepath"
"reflect"
"runtime"
"testing"
)
......@@ -56,3 +61,39 @@ func TestCleanHost(t *testing.T) {
}
}
}
// Test that cmd/go doesn't link in the HTTP server.
//
// This catches accidental dependencies between the HTTP transport and
// server code.
func TestCmdGoNoHTTPServer(t *testing.T) {
testenv.MustHaveGoBuild(t)
var exeSuffix string
if runtime.GOOS == "windows" {
exeSuffix = ".exe"
}
goBin := filepath.Join(runtime.GOROOT(), "bin", "go"+exeSuffix)
out, err := exec.Command("go", "tool", "nm", goBin).Output()
if err != nil {
t.Fatalf("go tool nm: %v", err)
}
wantSym := map[string]bool{
// Verify these exist: (sanity checking this test)
"net/http.(*Client).Get": true,
"net/http.(*Transport).RoundTrip": true,
// Verify these don't exist:
"net/http.http2Server": false,
"net/http.(*Server).Serve": false,
}
for sym, want := range wantSym {
got := bytes.Contains(out, []byte(sym))
if !want && got {
t.Errorf("cmd/go unexpectedly links in HTTP server code; found symbol %q in cmd/go", sym)
}
if want && !got {
t.Errorf("expected to find symbol %q in cmd/go; not found", sym)
}
}
}
......@@ -820,7 +820,18 @@ type maxBytesReader struct {
func (l *maxBytesReader) tooLarge() (n int, err error) {
if !l.stopped {
l.stopped = true
if res, ok := l.w.(*response); ok {
// The server code and client code both use
// maxBytesReader. This "requestTooLarge" check is
// only used by the server code. To prevent binaries
// which only using the HTTP Client code (such as
// cmd/go) from also linking in the HTTP server, don't
// use a static type assertion to the server
// "*response" type. Check this interface instead:
type requestTooLarger interface {
requestTooLarge()
}
if res, ok := l.w.(requestTooLarger); ok {
res.requestTooLarge()
}
}
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment