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f1ded84454
This adds a file that's not compiled by default that exists just to
make it easier to do binary size checks, probing what a binary would
be like if it included reflect methods (as used by html/template, etc).
As an example, once tailscaled uses reflect.Type.MethodByName(non-const-string) anywhere,
the build jumps up by 14.5 MB:
$ GOOS=linux GOARCH=amd64 ./tool/go build -tags=ts_include_cli,ts_omit_webclient,ts_omit_systray,ts_omit_debugeventbus -o before ./cmd/tailscaled
$ GOOS=linux GOARCH=amd64 ./tool/go build -tags=ts_include_cli,ts_omit_webclient,ts_omit_systray,ts_omit_debugeventbus,ts_debug_forcereflect -o after ./cmd/tailscaled
$ ls -l before after
-rwxr-xr-x@ 1 bradfitz staff 41011861 Sep 9 07:28 before
-rwxr-xr-x@ 1 bradfitz staff 55610948 Sep 9 07:29 after
This is particularly pronounced with large deps like the AWS SDK. If you compare using ts_omit_aws:
-rwxr-xr-x@ 1 bradfitz staff 38284771 Sep 9 07:40 no-aws-no-reflect
-rwxr-xr-x@ 1 bradfitz staff 45546491 Sep 9 07:41 no-aws-with-reflect
That means adding AWS to a non-reflect binary adds 2.7 MB but adding
AWS to a reflect binary adds 10 MB.
Updates #17063
Updates #12614
Change-Id: I18e9b77c9cf33565ce5bba65ac5584fa9433f7fb
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
27 lines
656 B
Go
27 lines
656 B
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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//go:build ts_debug_forcereflect
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// This file exists for benchmarking binary sizes. When the build tag is
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// enabled, it forces use of part of the reflect package that makes the Go
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// linker go into conservative retention mode where its deadcode pass can't
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// eliminate exported method.
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package main
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import (
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"reflect"
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"time"
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)
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func init() {
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// See Go's src/cmd/compile/internal/walk/expr.go:usemethod for
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// why this is isn't a const.
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name := []byte("Bar")
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if time.Now().Unix()&1 == 0 {
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name[0] = 'X'
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}
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_, _ = reflect.TypeOf(12).MethodByName(string(name))
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}
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