Empty ebpf import path in generated .go

[chent1996]

I tried to build ebpf with bpf2go on both the x86 and arm platforms but failed with arm because of the missing ebpf import path

// Code generated by bpf2go; DO NOT EDIT.

package bpf_core

import (
	"bytes"
	_ "embed"
	"fmt"
	"io"

	""
) 

with error:

2024/01/08 18:42:59 bazel-out/aarch64-fastbuild/bin/bpf_core/go_prog/from_lxc_v4nat_v6nat_bpf.go:6:2: could not import bytes (open : no such file or directory)
2024/01/08 18:42:59 bazel-out/aarch64-fastbuild/bin/bpf_core/go_prog/from_lxc_v4nat_v6nat_bpf.go:7:4: could not import embed (open : no such file or directory)
2024/01/08 18:42:59 bazel-out/aarch64-fastbuild/bin/bpf_core/go_prog/from_lxc_v4nat_v6nat_bpf.go:9:2: could not import io (open : no such file or directory)
2024/01/08 18:42:59 bazel-out/aarch64-fastbuild/bin/bpf_core/go_prog/from_lxc_v4nat_v6nat_bpf.go:11:2: invalid import path (empty string)

At first, I thought there was something to do with currentModule() in output.go but I think the module is not used to generate the ebpf path.

Since it works fine on x86, I'm not so sure if is there a problem with bpf2go or with my environment.

[lmb]

Do you have the most recent version? This might be another bazel bug.

ebpf/cmd/bpf2go/tools.go

Lines 88 to 90 in 394be60

	if !ok {
	// Fall back to constant since bazel doesn't support BuildInfo.
	return "github.com/cilium/ebpf"

[chent1996]

The problem is not with Bazel, it is a change introduced by go 1.18
golang/go#51831

If bpf2go is built with file arguments like go build -o bpf2go_arm64_debug ./cmd/bpf2go/*.go, then debug.ReadBuildInfo() will return ok but with empty buildInfo.Main

[florianl]

Just out of curiosity: Can you reproduce the issue with Go 1.20?
Asking, as the minimum supported Go version is Go 1.20 at the moment - see

ebpf/go.mod

Line 3 in 839118d

go 1.20

[chent1996]

I'm reproducing this with go 1.21.5

[lmb]

I'd argue that this is a non-standard way of building a package. Why not do go build -o bpf2go_arm64_debug ./cmd/bpf2go?