embed: document 2GB max file size ("file too large")

[hchargois]

What version of Go are you using (go version)?

$ go version
go version go1.16.7 linux/amd64

Does this issue reproduce with the latest release?

Yes, this is the latest release

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/hugo/.cache/go-build"
GOENV="/home/hugo/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/hugo/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/hugo/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.7"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/hugo/test/goembed/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build3344754598=/tmp/go-build -gno-record-gcc-switches"

What did you do?

1. Create a 2001 MB (not MiB) file: dd if=/dev/zero of=2001M bs=1MB count=2001
2. Try to embed it

package main

import (
	_ "embed"
	"fmt"
)

//go:embed 2001M
var embedded []byte

func main() {
	fmt.Println("hello", len(embedded))
}

What did you expect to see?

Successful build

What did you see instead?

Build error:

$ go build
# testgoembed
./main.go:9:5: embed 2001M: file too large

A 1999 MB (again, not MiB) file gets embedded without issue.

I think the cause is here: https://github.com/golang/go/blob/master/src/cmd/compile/internal/staticdata/data.go#L136-L142

Maybe it is unreasonable to embed 2 GB files, but if it is so, I think this size limit should be documented in the embed doc.

[gopherbot]

Change https://golang.org/cl/341689 mentions this issue: embed: document the maximum file size supported