Use Requires.private only for static linking

[otegami]

GitHub:

• Add MSYS2 platform package requirement #41 (comment)
• Add MSYS2 platform package requirement #41 (comment)

By default, exclude Requires.private dependencies from cflags and libs output to match pkgconf's
behavior.
When the new static: true option is specified,
include Requires.private dependencies for static linking scenarios.

This change makes the default behavior consistent with pkgconf while still supporting static linking
use-cases through an explicit option.

[otegami]

On Windows, some test failed because of cflags...

D:/rubyinstaller-head-x64/bin/ruby.exe test/run.rb
===============================================================================
Failure: test_cflags(PkgConfigTest)
D:/a/pkg-config/pkg-config/test/test-pkg-config.rb:203:in 'PkgConfigTest#assert_pkg_config'
D:/a/pkg-config/pkg-config/test/test-pkg-config.rb:38:in 'PkgConfigTest#test_cflags'
     35: 
     36:   def test_cflags
     37:     omit("Fragile on macOS") if RUBY_PLATFORM.include?("darwin")
  => 38:     assert_pkg_config("glib-2.0", ["--cflags"], @glib.cflags)
     39:   end
     40: 
     41:   def test_cflags_only_I
<"-ID:/rubyinstaller-head-x64/msys64/ucrt64/include/glib-2.0 -I/tmp/local/lib/glib-2.0/include -ID:/rubyinstaller-head-x64/msys64/ucrt64/include"> expected but was
<"-ID:/rubyinstaller-head-x64/msys64/ucrt64/include/glib-2.0 -I/tmp/local/lib/glib-2.0/include">

diff:
? -ID:/rubyinstaller-head-x64/msys64/ucrt64/include/glib-2.0 -I/tmp/local/lib/glib-2.0/include -ID:/rubyinstaller-head-x64/msys64/ucrt64/include
Error: <"-ID:/rubyinstaller-head-x64/msys64/ucrt64/include/glib-2.0 -I/tmp/local/lib/glib-2.0/include -ID:/rubyinstaller-head-x64/msys64/ucrt64/include"> expected but was
<"-ID:/rubyinstaller-head-x64/msys64/ucrt64/include/glib-2.0 -I/tmp/local/lib/glib-2.0/include">.

ref: https://github.com/otegami/pkg-config/actions/runs/19729356341/job/56526836780#step:9:24

---

The pkgconf's behavior might be different between RubyInstaller and MSYS2.

RubyInstaller (pkgconf 2.5.1)

Output includes Requires.private cflags.

pkgconf --cflags glib-2.0
-I.../include/glib-2.0 -I.../lib/glib-2.0/include -I.../include

MSYS2 (pkgconf 2.5.1)

Output does NOT include Requires.private cflags.

pkgconf --cflags glib-2.0
-I.../include/glib-2.0 -I.../lib/glib-2.0/include

[otegami]

The difference is caused by pkgconf's system include path filtering.

MSYS2 environment

In MSYS2, pkgconf recognizes '/ucrt64/include' as a system include path and excludes it by default.

Command	Output
pkgconf --cflags libpcre2-8	(empty)
pkgconf --cflags --keep-system-cflags libpcre2-8	-I.../ucrt64/include
pkgconf --cflags glib-2.0	2 paths (without /include)
pkgconf --cflags --keep-system-cflags glib-2.0	3 paths (with /include)

ref: https://github.com/otegami/pkg-config/actions/runs/19730472975/job/56530192519#step:5:97

Difference between RubyInstaller and MSYS2

• MSYS2: pkgconf excludes system paths (like /ucrt64/include) by default
• RubyInstaller: pkgconf does NOT exclude system paths (behaves like --keep-system-cflags)

This is likely due to different pkgconf build configurations or environment settings between the two?

[kou]

Could you show the results of pkgconf --dump-personality on RubyInstaller's MSYS2 and no-RubyInstaller MSYS2?

[otegami]

Could you show the results of pkgconf --dump-personality on RubyInstaller's MSYS2 and no-RubyInstaller MSYS2?

Sure, the result is the following.
I'm little bit confused now. I will sort of my thoughts too now on.

RubyInstaller's MSYS2

Run echo "=== pkgconf --version ==="
=== pkgconf --version ===
2.5.1

=== pkgconf --dump-personality ===
Triplet: default
DefaultSearchPaths: D:/rubyinstaller-head-x64/msys64/ucrt64/bin/../lib/pkgconfig D:/rubyinstaller-head-x64/msys64/ucrt64/bin/../share/pkgconfig 
SystemIncludePaths: /ucrt64/include 
SystemLibraryPaths: /ucrt64/lib 

no-RubyInstaller MSYS2

Run echo "=== pkgconf --version ==="
=== pkgconf --version ===
2.5.1

=== pkgconf --dump-personality ===
Triplet: default
DefaultSearchPaths: D:/a/_temp/msys64/ucrt64/bin/../lib/pkgconfig D:/a/_temp/msys64/ucrt64/bin/../share/pkgconfig 
SystemIncludePaths: /ucrt64/include 
SystemLibraryPaths: /ucrt64/lib 

[kou]

Could you also share pkgconf --help on both environments?

[otegami]

Could you also share pkgconf --help on both environments?

Sure.

RubyInstaller MSYS2

pkgconf --helpのログ

=== pkgconf --help ===
usage: pkgconf [OPTIONS] [LIBRARIES]

basic options:

  --help                            this message
  --about                           print pkgconf version and license to stdout
  --version                         print supported pkg-config version to stdout
  --verbose                         print additional information
  --atleast-pkgconfig-version       check whether or not pkgconf is compatible
                                    with a specified pkg-config version
  --errors-to-stdout                print all errors on stdout instead of stderr
  --print-errors                    ensure all errors are printed
  --short-errors                    be less verbose about some errors
  --silence-errors                  explicitly be silent about errors
  --list-all                        list all known packages
  --list-package-names              list all known package names
  --simulate                        simulate walking the calculated dependency graph
  --no-cache                        do not cache already seen packages when
                                    walking the dependency graph
  --log-file=filename               write an audit log to a specified file
  --with-path=path                  adds a directory to the search path
  --define-prefix                   override the prefix variable with one that is guessed based on
                                    the location of the .pc file
  --dont-define-prefix              do not override the prefix variable under any circumstances
  --prefix-variable=varname         sets the name of the variable that pkgconf considers
                                    to be the package prefix
  --relocate=path                   relocates a path and exits (mostly for testsuite)
  --dont-relocate-paths             disables path relocation support

cross-compilation personality support:

  --personality=triplet|filename    sets the personality to 'triplet' or a file named 'filename'
  --dump-personality                dumps details concerning selected personality

checking specific pkg-config database entries:

  --atleast-version                 require a specific version of a module
  --exact-version                   require an exact version of a module
  --max-version                     require a maximum version of a module
  --exists                          check whether or not a module exists
  --uninstalled                     check whether or not an uninstalled module will be used
  --no-uninstalled                  never use uninstalled modules when satisfying dependencies
  --no-provides                     do not use 'provides' rules to resolve dependencies
  --maximum-traverse-depth          maximum allowed depth for dependency graph
  --static                          be more aggressive when computing dependency graph
                                    (for static linking)
  --shared                          use a simplified dependency graph (usually default)
  --pure                            optimize a static dependency graph as if it were a normal
                                    dependency graph
  --env-only                        look only for package entries in PKG_CONFIG_PATH
  --ignore-conflicts                ignore 'conflicts' rules in modules
  --validate                        validate specific .pc files for correctness

querying specific pkg-config database fields:

  --define-variable=varname=value   define variable 'varname' as 'value'
  --variable=varname                print specified variable entry to stdout
  --cflags                          print required CFLAGS to stdout
  --cflags-only-I                   print required include-dir CFLAGS to stdout
  --cflags-only-other               print required non-include-dir CFLAGS to stdout
  --libs                            print required linker flags to stdout
  --libs-only-L                     print required LDPATH linker flags to stdout
  --libs-only-l                     print required LIBNAME linker flags to stdout
  --libs-only-other                 print required other linker flags to stdout
  --print-requires                  print required dependency frameworks to stdout
  --print-requires-private          print required dependency frameworks for static
                                    linking to stdout
  --print-provides                  print provided dependencies to stdout
  --print-variables                 print all known variables in module to stdout
  --digraph                         print entire dependency graph in graphviz 'dot' format
  --solution                        print dependency graph solution in a simple format
  --keep-system-cflags              keep -I/ucrt64/include entries in cflags output
  --keep-system-libs                keep -L/ucrt64/lib entries in libs output
  --path                            show the exact filenames for any matching .pc files
  --modversion                      print the specified module's version to stdout
  --internal-cflags                 do not filter 'internal' cflags from output
  --license                         print the specified module's license to stdout if known
  --exists-cflags                   add -DHAVE_FOO fragments to cflags for each found module

filtering output:

  --msvc-syntax                     print translatable fragments in MSVC syntax
  --fragment-filter=types           filter output fragments to the specified types
  --env=prefix                      print output as shell-compatible environmental variables
  --fragment-tree                   visualize printed CFLAGS/LIBS fragments as a tree

report bugs to <https://todo.sr.ht/~kaniini/pkgconf>.

no RubyInstaller MSYS2

pkgconf --helpのログ

=== pkgconf --help ===
usage: pkgconf [OPTIONS] [LIBRARIES]

basic options:

  --help                            this message
  --about                           print pkgconf version and license to stdout
  --version                         print supported pkg-config version to stdout
  --verbose                         print additional information
  --atleast-pkgconfig-version       check whether or not pkgconf is compatible
                                    with a specified pkg-config version
  --errors-to-stdout                print all errors on stdout instead of stderr
  --print-errors                    ensure all errors are printed
  --short-errors                    be less verbose about some errors
  --silence-errors                  explicitly be silent about errors
  --list-all                        list all known packages
  --list-package-names              list all known package names
  --simulate                        simulate walking the calculated dependency graph
  --no-cache                        do not cache already seen packages when
                                    walking the dependency graph
  --log-file=filename               write an audit log to a specified file
  --with-path=path                  adds a directory to the search path
  --define-prefix                   override the prefix variable with one that is guessed based on
                                    the location of the .pc file
  --dont-define-prefix              do not override the prefix variable under any circumstances
  --prefix-variable=varname         sets the name of the variable that pkgconf considers
                                    to be the package prefix
  --relocate=path                   relocates a path and exits (mostly for testsuite)
  --dont-relocate-paths             disables path relocation support

cross-compilation personality support:

  --personality=triplet|filename    sets the personality to 'triplet' or a file named 'filename'
  --dump-personality                dumps details concerning selected personality

checking specific pkg-config database entries:

  --atleast-version                 require a specific version of a module
  --exact-version                   require an exact version of a module
  --max-version                     require a maximum version of a module
  --exists                          check whether or not a module exists
  --uninstalled                     check whether or not an uninstalled module will be used
  --no-uninstalled                  never use uninstalled modules when satisfying dependencies
  --no-provides                     do not use 'provides' rules to resolve dependencies
  --maximum-traverse-depth          maximum allowed depth for dependency graph
  --static                          be more aggressive when computing dependency graph
                                    (for static linking)
  --shared                          use a simplified dependency graph (usually default)
  --pure                            optimize a static dependency graph as if it were a normal
                                    dependency graph
  --env-only                        look only for package entries in PKG_CONFIG_PATH
  --ignore-conflicts                ignore 'conflicts' rules in modules
  --validate                        validate specific .pc files for correctness

querying specific pkg-config database fields:

  --define-variable=varname=value   define variable 'varname' as 'value'
  --variable=varname                print specified variable entry to stdout
  --cflags                          print required CFLAGS to stdout
  --cflags-only-I                   print required include-dir CFLAGS to stdout
  --cflags-only-other               print required non-include-dir CFLAGS to stdout
  --libs                            print required linker flags to stdout
  --libs-only-L                     print required LDPATH linker flags to stdout
  --libs-only-l                     print required LIBNAME linker flags to stdout
  --libs-only-other                 print required other linker flags to stdout
  --print-requires                  print required dependency frameworks to stdout
  --print-requires-private          print required dependency frameworks for static
                                    linking to stdout
  --print-provides                  print provided dependencies to stdout
  --print-variables                 print all known variables in module to stdout
  --digraph                         print entire dependency graph in graphviz 'dot' format
  --solution                        print dependency graph solution in a simple format
  --keep-system-cflags              keep -I/ucrt64/include entries in cflags output
  --keep-system-libs                keep -L/ucrt64/lib entries in libs output
  --path                            show the exact filenames for any matching .pc files
  --modversion                      print the specified module's version to stdout
  --internal-cflags                 do not filter 'internal' cflags from output
  --license                         print the specified module's license to stdout if known
  --exists-cflags                   add -DHAVE_FOO fragments to cflags for each found module

filtering output:

  --msvc-syntax                     print translatable fragments in MSVC syntax
  --fragment-filter=types           filter output fragments to the specified types
  --env=prefix                      print output as shell-compatible environmental variables
  --fragment-tree                   visualize printed CFLAGS/LIBS fragments as a tree

report bugs to <https://todo.sr.ht/~kaniini/pkgconf>.

[otegami]

I looked into the pkgconf source code. It seems that pkgconf includes Requires.private cflags by default.
The following filtering only happens when the path matches a system include path.

if (!(want_flags & PKG_KEEP_SYSTEM_CFLAGS) && pkgconf_fragment_has_system_dir(client, frag))
    return false;

ref: https://github.com/pkgconf/pkgconf/blob/a1e09753bc4353fdd21957f6c1fd55d7e53662e4/cli/main.c#L136-L137

To match pkgconf's behavior, we need to implement this system path filtering in the pkg-config gem.

[kou]

It seems that pkgconf includes Requires.private cflags by default.

How did you confirm it?

Could you share the result of pkgconf --debug --cflags re2 on both environments? (They will be very large. We may want to redirect the outputs to files and upload them.)

[otegami]

I confirmed it using the following information.
In pkgconf_pkg_traverse_main, both Requires and Requires.private are always walked when collecting cflags:

• ref: https://github.com/pkgconf/pkgconf/blob/a1e09753bc4353fdd21957f6c1fd55d7e53662e4/libpkgconf/pkg.c#L1795-L1805

This is also documented in the NEWS file.

• Document that Requires.private is always used for header paths.

• ref: https://github.com/pkgconf/pkgconf/blob/a1e09753bc4353fdd21957f6c1fd55d7e53662e4/NEWS#L111-L112

---

Could you share the result of pkgconf --debug --cflags re2 on both environments? (They will be very large. We may want to redirect the outputs to files and upload them.)

I will check it now.

[kou]

Then, we should keep the current implementation (use Requires.private for shared/static linking), right?

[otegami]

Yes. So I will close this PR because this specification doesn't follow pkgconf's behaviors.