Allow compilation on older gcc versions

[adfoster-r7]

What problem is this PR intended to solve?

Compiling Nokogiri with older versions of GCC and centos causes the following error:

12:06:09 checking for gumbo_parse_with_options() in nokogiri_gumbo.h... yes
12:06:09 checking for xmlHasFeature()... yes
12:06:09 checking for xmlFirstElementChild()... yes
12:06:09 checking for xmlRelaxNGSetParserStructuredErrors()... yes
12:06:09 checking for xmlRelaxNGSetValidStructuredErrors()... yes
12:06:09 checking for xmlSchemaSetValidStructuredErrors()... yes
12:06:09 checking for xmlSchemaSetParserStructuredErrors()... yes
12:06:09 checking for rb_category_warning()... yes
12:06:09 checking for whether
12:06:09 -DNOKOGIRI_OTHER_LIBRARY_VERSIONS="\"libgumbo:1.0.0-nokogiri\"" is accepted as
12:06:09 CPPFLAGS... yes
12:06:09 creating Makefile
12:06:09 
12:06:09 current directory:
12:06:09 /opt/dev/embedded/lib/ruby/gems/3.0.0/gems/nokogiri-1.16.0/ext/nokogiri
12:06:09 make DESTDIR\= clean
12:06:09 
12:06:09 current directory:
12:06:09 /opt/dev/embedded/lib/ruby/gems/3.0.0/gems/nokogiri-1.16.0/ext/nokogiri
12:06:09 make DESTDIR\=
12:06:09 compiling gumbo.c
12:06:09 compiling html4_document.c
12:06:09 compiling html4_element_description.c
12:06:09 compiling html4_entity_lookup.c
12:06:09 compiling html4_sax_parser_context.c
12:06:09 compiling html4_sax_push_parser.c
12:06:09 compiling libxml2_backwards_compat.c
12:06:09 compiling nokogiri.c
12:06:09 compiling test_global_handlers.c
12:06:09 compiling xml_attr.c
12:06:09 compiling xml_attribute_decl.c
12:06:09 compiling xml_cdata.c
12:06:09 compiling xml_comment.c
12:06:09 compiling xml_document.c
12:06:09 xml_document.c: In function 'dealloc':
12:06:09 xml_document.c:77: error: #pragma GCC diagnostic not allowed inside functions
12:06:09 xml_document.c:78: error: #pragma GCC diagnostic not allowed inside functions
12:06:09 xml_document.c:90: warning: '__xmlDeregisterNodeDefaultValue' is deprecated
12:06:09 (declared at
12:06:09 /opt/dev/embedded/lib/ruby/gems/3.0.0/gems/nokogiri-1.16.0/ports/x86_64-linux/libxml2/2.12.3/include/libxml2/libxml/tree.h:684)
12:06:09 xml_document.c:93: error: #pragma GCC diagnostic not allowed inside functions
12:06:09 make: *** [xml_document.o] Error 1
12:06:09 
12:06:09 make failed, exit code 2
12:06:09 
12:06:09 Gem files will remain installed in
12:06:09 /opt/dev/embedded/lib/ruby/gems/3.0.0/gems/nokogiri-1.16.0 for
12:06:09 inspection.
12:06:09 Results logged to
12:06:09 /opt/dev/embedded/lib/ruby/gems/3.0.0/extensions/x86_64-linux/3.0.0/nokogiri-1.16.0/gem_make.out
12:06:09 
12:06:09 An error occurred while installing nokogiri (1.16.0), and Bundler cannot
12:06:09 continue.
12:06:09 Make sure that `gem install nokogiri -v '1.16.0' --source
12:06:09 'https://rubygems.org/'` succeeds before bundling.
12:06:09 
12:06:09 In Gemfile:
12:06:09   factory_bot_rails was resolved to 6.2.0, which depends on
12:06:09     railties was resolved to 7.0.8, which depends on
12:06:09       actionpack was resolved to 7.0.8, which depends on
12:06:09         actionview was resolved to 7.0.8, which depends on
12:06:09           rails-dom-testing was resolved to 2.2.0, which depends on
12:06:09             nokogiri

Have you included adequate test coverage?

No tests have been added; the solution implemented is similar to redis/redis#5394 - and has been verified as working locally in a fresh docker container

Does this change affect the behavior of either the C or the Java implementations?

Impacts the C behavior

[stevecheckoway]

This looks like the right approach to me. Running the CI now.

I'm not sure how to tell which version of GCC support which pragmas where though.

[adfoster-r7]

I believe GCC versions prior to 4.6 are impacted - https://gcc.gnu.org/gcc-4.6/changes.html

New Languages and Language specific improvements

C family

• ...
• Support for selectively enabling and disabling warnings via #pragma GCC diagnostic has been added. For instance:

#pragma GCC diagnostic error "-Wuninitialized"
 foo(a);			/* error is given for this one */
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wuninitialized"
 foo(b);			/* no diagnostic for this one */
#pragma GCC diagnostic pop
 foo(c);			/* error is given for this one */
#pragma GCC diagnostic pop
 foo(d);			/* depends on command-line options */

I aligned with the approach taken by Redis for simplicity; Although I think that this could be tightened up a bit to check for minor version too

# https://gcc.gnu.org/onlinedocs/cpp/Common-Predefined-Macros.html
/* Test for GCC > 3.2.0 */
#if __GNUC__ > 3 || \
    (__GNUC__ == 3 && (__GNUC_MINOR__ > 2 || \
                       (__GNUC_MINOR__ == 2 && \
                        __GNUC_PATCHLEVEL__ > 0))

I'm happy to go with whatever check you think is best - I just know the currently suggested fix works for centos

[flavorjones]

I'd love to be able to test this manually, but I couldn't easily find a docker image with gcc 4.6 or earlier. Do you know of one you can point me at? The centos:centos6 image will no longer yum update, and the gcc:4.6 image has old CA certs so I can't git clone.

I mean, I'm happy to merge this without testing it, too, if you're sure this solves your problem. Let me know?

[adfoster-r7]

@flavorjones These replication steps should hopefully work

1. Git clone nokogiri on the host machine - or it can be git cloned inside the docker container
2. In the same directory run the docker container. It's centos 6 with gcc (GCC) 4.4.7

# Run the container from the same directory as nokogiri - or don't do use volume mounts, and just git clone inside
docker run --rm  -i --tty -u jenkins --volume=$(pwd):$(pwd) -w $(pwd) rapid7/msf-centos6-x64-omnibus:2024_01 /bin/bash --login

# Install bundler
gem install bundler -v 2.3

# libyaml
sudo yum install -y libyaml-devel

# Bundle
bundle

# Compile nokogiri
bundle exec rake clean
bundle exec rake compile:nokogiri -- --use-system-libraries

Before

failure

$ bundle exec rake compile:nokogiri -- --use-system-libraries
....
/var/jenkins_home/.rvm/rubies/ruby-3.0.6/include/ruby-3.0.0/ruby/internal/arithmetic/int.h:155: warning: comparison is always true due to limited range of data type
../../../../ext/nokogiri/xml_document.c: In function ‘dealloc’:
../../../../ext/nokogiri/xml_document.c:77: error: #pragma GCC diagnostic not allowed inside functions
../../../../ext/nokogiri/xml_document.c:78: error: #pragma GCC diagnostic not allowed inside functions
../../../../ext/nokogiri/xml_document.c:93: error: #pragma GCC diagnostic not allowed inside functions
At top level:
cc1: warning: unrecognized command line option "-Wno-tautological-compare"
cc1: warning: unrecognized command line option "-Wno-self-assign"
cc1: warning: unrecognized command line option "-Wno-parentheses-equality"
cc1: warning: unrecognized command line option "-Wno-constant-logical-operand"
cc1: warning: unrecognized command line option "-Wno-cast-function-type"
gmake: *** [xml_document.o] Error 1
rake aborted!
Command failed with status (2): [/usr/bin/gmake]
/var/jenkins_home/.rvm/gems/ruby-3.0.6/gems/rake-compiler-1.2.5/lib/rake/extensiontask.rb:195:in `block (2 levels) in define_compile_tasks'
/var/jenkins_home/.rvm/gems/ruby-3.0.6/gems/rake-compiler-1.2.5/lib/rake/extensiontask.rb:194:in `block in define_compile_tasks'
/var/jenkins_home/.rvm/gems/ruby-3.0.6/gems/rake-13.1.0/exe/rake:27:in `<top (required)>'
/var/jenkins_home/.rvm/gems/ruby-3.0.6/bin/ruby_executable_hooks:22:in `eval'
/var/jenkins_home/.rvm/gems/ruby-3.0.6/bin/ruby_executable_hooks:22:in `<main>'
Tasks: TOP => compile:nokogiri => compile:nokogiri:x86_64-linux => copy:nokogiri:x86_64-linux:3.0.6 => tmp/x86_64-linux/nokogiri/3.0.6/nokogiri.so
(See full trace by running task with --trace)

After

success

$ bundle exec rake compile:nokogiri -- --use-system-libraries
cp tmp/x86_64-linux/nokogiri/3.0.6/nokogiri.so tmp/x86_64-linux/stage/lib/nokogiri/nokogiri.so
[jenkins@c4d13ce50246 nokogiri]$ echo $?
0
...

[flavorjones]

@adfoster-r7 Thank you for your help, and for submitting this. Looks good to me, will merge and get into the next patch release.