Cross-compiling from linux to windows

[hans-m-song]

I seem to be having some issues cross-compiling from linux to windows.

Here is a reproducible example:

Dockerfile

FROM --platform=linux/amd64 ubuntu:20.04

ENV DEBIAN_FRONTEND=noninteractive
RUN apt-get update && \
  apt-get install -y \
  ca-certificates \
  curl \
  gcc-mingw-w64 \
  libc6 \
  libc6-dev \
  libxml2 \
  libxml2-dev \
  pkg-config

RUN curl -Lf "https://go.dev/dl/go1.18.3.linux-amd64.tar.gz" -o "go.tar.gz" \
  && tar -C /usr/local -xzf go.tar.gz \
  && rm -f go.tar.gz \
  && mkdir -p /home/test
ENV PATH=/usr/local/go/bin:$PATH

WORKDIR /home/test
COPY go.mod main.go ./
RUN go mod tidy

ENV GOOS=windows
ENV CC=x86_64-w64-mingw32-gcc
ENV CGO_ENABLED=1
ENV GOARCH=amd64
ENV CGO_CFLAGS=-I/usr/include

# this fails!
RUN go build

go.mod

module test

go 1.18

require (
    github.com/lestrrat/go-libxml2 v0.0.0-20180221004755-bb78334e2019
)

main.go

package main

import (
    "github.com/lestrrat/go-libxml2/xsd"
)

func main() {
    xsd.ParseFromFile("")
}

Attempting to build the image results in the following error:

# github.com/lestrrat/go-libxml2/clib
In file included from /usr/include/libxml2/libxml/parser.h:810,
                 from /usr/include/libxml2/libxml/HTMLparser.h:16,
                 from /root/go/pkg/mod/github.com/lestrrat/go-libxml2@v0.0.0-20180221004755-bb78334e2019/clib/clib.go:28:
/usr/include/libxml2/libxml/encoding.h:28:10: fatal error: iconv.h: No such file or directory
   28 | #include <iconv.h>
      |          ^~~~~~~~~
compilation terminated.

Using CGO_FLAGS=-I/usr/include doesn't seem to help either.

I can see the file /usr/include/iconv.h exists if built omitting the failing step in the dockerfile and pkg-config recognises libxml2.

# pkg-config --list-all
shared-mime-info shared-mime-info - Freedesktop common MIME database
libxcrypt        libxcrypt - Extended crypt library for DES, MD5, Blowfish and others
icu-uc           icu-uc - International Components for Unicode: Common and Data libraries
icu-i18n         icu-i18n - International Components for Unicode: Internationalization library
libxml-2.0       libXML - libXML library version2.
libcrypt         libxcrypt - Extended crypt library for DES, MD5, Blowfish and others
icu-io           icu-io - International Components for Unicode: Stream and I/O Library

Sorry if this is the wrong place to put this, I figure this is more to do with cgo than libxml2 but I'm at a loss as to how to proceed. Probably similar to https://github.com/lestrrat-go/libxml2/issues/80 (I have encountered their issue as well).

[lestrrat]

I'm not much of an expert around this, but one thing I suspect is that libxml2 was not installed with /usr/include ?

What does pkg-config --libs libxml2 tell you?

[hans-m-song]

Here is the output:

# pkg-config --libs libxml2
Package libxml2 was not found in the pkg-config search path.
Perhaps you should add the directory containing `libxml2.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libxml2' found

I take it you are expecting libxml2 instead of libxml-2.0?

When building with -x

# go build -x
WORK=/tmp/go-build3518064176
mkdir -p $WORK/b003/
cd /root/go/pkg/mod/github.com/lestrrat/go-libxml2@v0.0.0-20180221004755-bb78334e2019/clib
pkg-config --cflags -- libxml-2.0
pkg-config --libs -- libxml-2.0
TERM='dumb' CGO_LDFLAGS='"-g" "-O2" "-lxml2"' /usr/local/go/pkg/tool/linux_amd64/cgo -objdir $WORK/b003/ -importpath github.com/lestrrat/go-libxml2/clib -- -I/usr/include/libxml2 -I $WORK/b003/ -g -O2 ./clib.go
# github.com/lestrrat/go-libxml2/clib
In file included from /usr/include/libxml2/libxml/parser.h:810,
                 from /usr/include/libxml2/libxml/HTMLparser.h:16,
                 from /root/go/pkg/mod/github.com/lestrrat/go-libxml2@v0.0.0-20180221004755-bb78334e2019/clib/clib.go:28:
/usr/include/libxml2/libxml/encoding.h:28:10: fatal error: iconv.h: No such file or directory
   28 | #include <iconv.h>
      |          ^~~~~~~~~
compilation terminated.

It references /usr/include/libxml2 which I can verify does contain header files

[lestrrat]

Oh, now that I think about it, did you install libxml2-dev or libxml2-devel or whatever it is?

[hans-m-song]

Yes I have, if you have a look at the Dockerfile, I have installed

• pkg-config
• gcc-mingw-w64 for cross-compilation
• libc6, libc6-dev which I believe contains libiconv
• libxml2, libxml2-dev

[lestrrat]

Oh, hmm... sorry now I'm stumped. :/

[hans-m-song]

No worries, I figured it's not really an issue with your package (which I have found quite useful, thanks for that!). I will keep digging. Feel free to close this.

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