bundle exec rake compile gets `error: incompatible function pointer types

[yahonda]

bundle exec rake compile gets `error: incompatible function pointer types.

Steps to reproduce

git clone https://github.com/xml4r/libxml-ruby
cd libxml-ruby
bundle install
bundle exec rake compile

Expected behavior

It should build libxml-ruby

Actual behavior

It gets ../../../../ext/libxml/ruby_xml_error.c:123:35: error: incompatible function pointer types passing 'void (void *, const xmlError *)' (aka 'void (void *, const struct _xmlError *)') to parameter of type 'xmlStructuredErrorFunc' (aka 'void (*)(void *, struct _xmlError *)') [-Wincompatible-function-pointer-types]

% bundle exec rake compile
mkdir -p tmp/x86_64-darwin23/libxml_ruby/3.3.0
cd tmp/x86_64-darwin23/libxml_ruby/3.3.0
/Users/yahonda/.rbenv/versions/3.3.0/bin/ruby -I. ../../../../ext/libxml/extconf.rb --with-xml2-include=/usr/include/libxml2
checking for libxml/xmlversion.h in /opt/include/libxml2,/opt/local/include/libxml2,/opt/homebrew/opt/libxml2/include/libxml2,/usr/local/include/libxml2,/usr/include/libxml2,/usr/local/include,/usr/local/opt/libxml2/include/libxml2... yes
checking for xmlParseDoc() in -lxml2... yes
creating extconf.h
creating Makefile
cd -
cd tmp/x86_64-darwin23/libxml_ruby/3.3.0
/usr/bin/make
compiling ../../../../ext/libxml/libxml.c
compiling ../../../../ext/libxml/ruby_xml.c
compiling ../../../../ext/libxml/ruby_xml_attr.c
compiling ../../../../ext/libxml/ruby_xml_attr_decl.c
compiling ../../../../ext/libxml/ruby_xml_attributes.c
compiling ../../../../ext/libxml/ruby_xml_cbg.c
compiling ../../../../ext/libxml/ruby_xml_document.c
compiling ../../../../ext/libxml/ruby_xml_dtd.c
compiling ../../../../ext/libxml/ruby_xml_encoding.c
compiling ../../../../ext/libxml/ruby_xml_error.c
../../../../ext/libxml/ruby_xml_error.c:123:35: error: incompatible function pointer types passing 'void (void *, const xmlError *)' (aka 'void (void *, const struct _xmlError *)') to parameter of type 'xmlStructuredErrorFunc' (aka 'void (*)(void *, struct _xmlError *)') [-Wincompatible-function-pointer-types]
  xmlSetStructuredErrorFunc(NULL, structuredErrorFunc);
                                  ^~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/libxml/xmlerror.h:870:29: note: passing argument to parameter 'handler' here
                                 xmlStructuredErrorFunc handler);
                                                        ^
1 error generated.
make: *** [ruby_xml_error.o] Error 1
rake aborted!
Command failed with status (2): [/usr/bin/make]
/Users/yahonda/.rbenv/versions/3.3.0/bin/bundle:25:in `load'
/Users/yahonda/.rbenv/versions/3.3.0/bin/bundle:25:in `<main>'
Tasks: TOP => compile => compile:x86_64-darwin23 => compile:libxml_ruby:x86_64-darwin23 => copy:libxml_ruby:x86_64-darwin23:3.3.0 => tmp/x86_64-darwin23/libxml_ruby/3.3.0/libxml_ruby.bundle
(See full trace by running task with --trace)
%

Environment

% ruby -v
ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-darwin23]

% sw_vers
ProductName:        macOS
ProductVersion:     14.4
BuildVersion:       23E214
% xcodebuild -version
Xcode 15.3
Build version 15E204a
% brew info libxml2                                                                                                                                                                                                   master
==> libxml2: stable 2.12.5 (bottled), HEAD [keg-only]
GNOME XML library
http://xmlsoft.org/
/usr/local/Cellar/libxml2/2.12.5_1 (204 files, 6.2MB)
  Poured from bottle using the formulae.brew.sh API on 2024-02-26 at 21:04:08
From: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/lib/libxml2.rb
License: MIT
==> Dependencies
Build: python-setuptools ✔, [email protected] ✔, [email protected] ✘
Required: icu4c ✔, readline ✔
==> Options
--HEAD
	Install HEAD version
==> Caveats
libxml2 is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.

If you need to have libxml2 first in your PATH, run:
  echo 'export PATH="/usr/local/opt/libxml2/bin:$PATH"' >> ~/.zshrc

For compilers to find libxml2 you may need to set:
  export LDFLAGS="-L/usr/local/opt/libxml2/lib"
  export CPPFLAGS="-I/usr/local/opt/libxml2/include"

For pkg-config to find libxml2 you may need to set:
  export PKG_CONFIG_PATH="/usr/local/opt/libxml2/lib/pkgconfig"
==> Analytics
install: 55,215 (30 days), 145,337 (90 days), 519,439 (365 days)
install-on-request: 19,307 (30 days), 48,113 (90 days), 177,149 (365 days)
build-error: 2 (30 days)
%

[yahonda]

I've found https://bugs.freebsd.org/bugzilla/attachment.cgi?id=248824&action=diff addresses this issue for macOS also.

[cfis]

Hmm, did libxml change this definition?

https://gnome.pages.gitlab.gnome.org/libxml2/devhelp/libxml2-xmlerror.html#xmlStructuredErrorFunc

void xmlStructuredErrorFunc(void * userData,  const xmlError * error)

[yahonda]

Looks like yes.

https://gitlab.gnome.org/GNOME/libxml2/-/commit/61034116d0a3c8b295c6137956adc3ae55720711

[cfis]

I see. Do you have time to create a PR?

[yahonda]

Sure.

[yahonda]

Opened #214