x/sys/unix: Definition for O_PATH missing for most FreeBSD architectures

[dfr]

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

$ go version
go version go1.18.2 freebsd/amd64

Does this issue reproduce with the latest release?

yes

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/dfr/.cache/go-build"
GOENV="/home/dfr/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="freebsd"
GOINSECURE=""
GOMODCACHE="/home/dfr/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="freebsd"
GOPATH="/home/dfr/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/freebsd_amd64"
GOVCS=""
GOVERSION="go1.18.2"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="cc"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/home/dfr/go/src/github.com/containers/podman/go.mod"
GOWORK=""
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 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build3986639741=/tmp/go-build -gno-record-gcc-switches"

What did you do?

import "golang.org/x/sys/unix" and try to use unix.O_PATH on FreeBSD 13.1 or later

What did you expect to see?

The program should compile

What did you see instead?

the program does not compile

Notes

This symbol has been present in FreeBSD system headers since 13.1-RELEASE. The generated go code in x/sys/unix contains a definition for riscv in zerrors_freebsd_riscv64.go but the constant is missing for all other architectures. This symbol is not arch-dependent and should have the same value on all supported architectures.

[dmgk]

I think adding O_PATH definition was a bit premature, given that the minimum supported FreeBSD version in go1.20 is 12.3, which lacks O_PATH support.

[dmgk]

cc @golang/freebsd

[dfr]

As far as I can tell, attempting to use the O_PATH flag on 12.3 will just ignore it and open the directory as a file which probably isn't ideal. In my case, I only plan to use thie in FreeBSD 13.1 or later but perhaps pubishing the symbol in x/sys/unix isn't ideal if 12.x is a supported release. The value for O_PATH does not conflict with any other flags supported in 12.x.

My workaround is to define the O_PATH constant in the application code which is a bit of a mess but otherwise should work.

[dmgk]

My concern is that writing/testing application on 13.1 and then using it on 12.3 might create a false assumption that it implements something that in fact is not supported by the host OS.

[paulzhol]

I'm with agreement with @dmgk here, the zerrors_freebsd_riscv64.go should have been generated under a 12.3 Jail.

[dfr]

Makes sense - thanks for the added context. When my work-in-progress (podman on FreeBSD) makes it to the FreeBSD ports/package tree, I'll make sure its only built for 13.1 or later.

[ayang64]

@paulzhol -- all of the 12.x releases will probably be EOL'd December 2023.

would it be reasonable to include its definition at that time and close this issue?

[dfr]

That seems reasonable. I guess this would change all the references to stable/12 in mkall.sh to stable/13 which would pick up any other additions to the ABI post 12.x