Switch to using libpkg-config instead of libpkgconf by default

The use of (now deprecated) libpkgconf is still possible by setting
config.build2.libpkgconf to true. Note that libpkgconf is known to
have issues on Windows and Mac OS so this should only be used on
Linux and maybe BSDs. Also note that we will only keep this until
upstream (again) breaks backwards compatibility at which point we
will drop this support.

3 files changed, 276 insertions, 7 deletions

diff --git a/libbuild2/cc/buildfile b/libbuild2/cc/buildfile
index e98e3de..e090e76 100644
--- a/libbuild2/cc/buildfile
+++ b/libbuild2/cc/buildfile
@@ -6,15 +6,24 @@
 include ../
 impl_libs = ../lib{build2} # Implied interface dependency.
 
-import impl_libs += libpkgconf%lib{pkgconf}
+libpkgconf = $config.build2.libpkgconf
+
+if $libpkgconf
+  import impl_libs += libpkgconf%lib{pkgconf}
+else
+  import impl_libs += libpkg-config%lib{pkg-config}
 
 include ../bin/
 intf_libs = ../bin/lib{build2-bin}
 
-./: lib{build2-cc}: libul{build2-cc}: {hxx ixx txx cxx}{** -**.test...} \
-  h{msvc-setup}                                                         \
+./: lib{build2-cc}: libul{build2-cc}:               \
+  {hxx ixx txx cxx}{** -pkgconfig-lib* -**.test...} \
+  h{msvc-setup}                                     \
   $intf_libs $impl_libs
 
+libul{build2-cc}: cxx{pkgconfig-libpkgconf}: include = $libpkgconf
+libul{build2-cc}: cxx{pkgconfig-libpkg-config}: include = (!$libpkgconf)
+
 # Unit tests.
 #
 exe{*.test}:
@@ -38,6 +47,9 @@ for t: cxx{**.test...}
 obja{*}: cxx.poptions += -DLIBBUILD2_CC_STATIC_BUILD
 objs{*}: cxx.poptions += -DLIBBUILD2_CC_SHARED_BUILD
 
+if $libpkgconf
+  cxx.poptions += -DBUILD2_LIBPKGCONF
+
 if ($cxx.target.class == 'windows')
   cxx.libs += $regex.apply(advapi32 ole32 oleaut32,        \
                            '(.+)',                         \
diff --git a/libbuild2/cc/pkgconfig-libpkg-config.cxx b/libbuild2/cc/pkgconfig-libpkg-config.cxx
new file mode 100644
index 0000000..f30a598
--- /dev/null
+++ b/libbuild2/cc/pkgconfig-libpkg-config.cxx
@@ -0,0 +1,251 @@
+// file      : libbuild2/cc/pkgconfig-libpkg-config.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BUILD2_BOOTSTRAP
+
+#include <libbuild2/cc/pkgconfig.hxx>
+
+#include <new> // std::bad_alloc
+
+#include <libbuild2/diagnostics.hxx>
+
+namespace build2
+{
+  namespace cc
+  {
+    // The package dependency traversal depth limit.
+    //
+    static const int max_depth = 100;
+
+    static void
+    error_handler (unsigned int,
+                   const char* msg,
+                   const pkg_config_client_t*,
+                   const void*)
+    {
+      error << msg;
+    }
+
+    // Deleters.
+    //
+    struct fragments_deleter
+    {
+      void operator() (pkg_config_list_t* f) const
+      {
+        pkg_config_fragment_free (f);
+      }
+    };
+
+    // Convert fragments to strings. Skip the -I/-L options that refer to
+    // system directories.
+    //
+    static strings
+    to_strings (const pkg_config_list_t& frags,
+                char type,
+                const pkg_config_list_t& sysdirs)
+    {
+      assert (type == 'I' || type == 'L');
+
+      strings r;
+      auto add = [&r] (const pkg_config_fragment_t* frag)
+      {
+        string s;
+        if (frag->type != '\0')
+        {
+          s += '-';
+          s += frag->type;
+        }
+
+        s += frag->data;
+        r.push_back (move (s));
+      };
+
+      // Option that is separated from its value, for example:
+      //
+      // -I /usr/lib
+      //
+      const pkg_config_fragment_t* opt (nullptr);
+
+      pkg_config_node_t *node;
+      LIBPKG_CONFIG_FOREACH_LIST_ENTRY(frags.head, node)
+      {
+        auto frag (static_cast<const pkg_config_fragment_t*> (node->data));
+
+        // Add the separated option and directory, unless the latest is a
+        // system one.
+        //
+        if (opt != nullptr)
+        {
+          assert (frag->type == '\0'); // See pkg_config_fragment_add().
+
+          if (!pkg_config_path_match_list (frag->data, &sysdirs))
+          {
+            add (opt);
+            add (frag);
+          }
+
+          opt = nullptr;
+          continue;
+        }
+
+        // Skip the -I/-L option if it refers to a system directory.
+        //
+        if (frag->type == type)
+        {
+          // The option is separated from a value, that will (presumably)
+          // follow.
+          //
+          if (*frag->data == '\0')
+          {
+            opt = frag;
+            continue;
+          }
+
+          if (pkg_config_path_match_list (frag->data, &sysdirs))
+            continue;
+        }
+
+        add (frag);
+      }
+
+      if (opt != nullptr) // Add the dangling option.
+        add (opt);
+
+      return r;
+    }
+
+    // Note that some libpkg-config functions can potentially return NULL,
+    // failing to allocate the required memory block. However, we will not
+    // check the returned value for NULL as the library doesn't do so, prior
+    // to filling the allocated structures. So such a code complication on our
+    // side would be useless. Also, for some functions the NULL result has a
+    // special semantics, for example "not found". @@ TODO: can we fix this?
+    //
+    pkgconfig::
+    pkgconfig (path_type p,
+               const dir_paths& pc_dirs,
+               const dir_paths& sys_lib_dirs,
+               const dir_paths& sys_hdr_dirs)
+        : path (move (p))
+    {
+      auto add_dirs = [] (pkg_config_list_t& dir_list,
+                          const dir_paths& dirs,
+                          bool suppress_dups)
+      {
+        for (const auto& d: dirs)
+          pkg_config_path_add (d.string ().c_str (), &dir_list, suppress_dups);
+      };
+
+      // Initialize the client handle.
+      //
+      // Note: omit initializing the filters from environment/defaults.
+      //
+      unique_ptr<pkg_config_client_t, void (*) (pkg_config_client_t*)> c (
+        pkg_config_client_new (&error_handler,
+                               nullptr /* handler_data */,
+                               false   /* init_filters */),
+        [] (pkg_config_client_t* c) {pkg_config_client_free (c);});
+
+      if (c == nullptr)
+        throw std::bad_alloc ();
+
+      add_dirs (c->filter_libdirs, sys_lib_dirs, false /* suppress_dups */);
+      add_dirs (c->filter_includedirs, sys_hdr_dirs, false /* suppress_dups */);
+
+      // Note that the loaded file directory is added to the (for now empty)
+      // .pc file search list. Also note that loading of the dependency
+      // packages is delayed until the flags retrieval, and their file
+      // directories are not added to the search list.
+      //
+      // @@ Hm, is there a way to force this resolution? But we may not
+      //    need this (e.g., only loading from variables).
+      //
+      pkg_ = pkg_config_pkg_find (c.get (), path.string ().c_str ());
+
+      if (pkg_ == nullptr)
+        fail << "package '" << path << "' not found or invalid";
+
+      // Add the .pc file search directories.
+      //
+      assert (c->dir_list.length == 1); // Package file directory (see above).
+      add_dirs (c->dir_list, pc_dirs, true /* suppress_dups */);
+
+      client_ = c.release ();
+    }
+
+    void pkgconfig::
+    free ()
+    {
+      assert (client_ != nullptr && pkg_ != nullptr);
+
+      pkg_config_pkg_unref (client_, pkg_);
+      pkg_config_client_free (client_);
+    }
+
+    strings pkgconfig::
+    cflags (bool stat) const
+    {
+      assert (client_ != nullptr); // Must not be empty.
+
+      pkg_config_client_set_flags (
+        client_,
+        // Walk through the private package dependencies (Requires.private)
+        // besides the public ones while collecting the flags. Note that we do
+        // this for both static and shared linking. @@ Hm, I wonder why...?
+        //
+        LIBPKG_CONFIG_PKG_PKGF_SEARCH_PRIVATE |
+
+        // Collect flags from Cflags.private besides those from Cflags for the
+        // static linking.
+        //
+        (stat
+         ? LIBPKG_CONFIG_PKG_PKGF_ADD_PRIVATE_FRAGMENTS
+         : 0));
+
+      pkg_config_list_t f = LIBPKG_CONFIG_LIST_INITIALIZER; // Empty list.
+      int e (pkg_config_pkg_cflags (client_, pkg_, &f, max_depth));
+
+      if (e != LIBPKG_CONFIG_PKG_ERRF_OK)
+        throw failed (); // Assume the diagnostics is issued.
+
+      unique_ptr<pkg_config_list_t, fragments_deleter> fd (&f);
+      return to_strings (f, 'I', client_->filter_includedirs);
+    }
+
+    strings pkgconfig::
+    libs (bool stat) const
+    {
+      assert (client_ != nullptr); // Must not be empty.
+
+      pkg_config_client_set_flags (
+        client_,
+        // Additionally collect flags from the private dependency packages
+        // (see above) and from the Libs.private value for the static linking.
+        //
+        (stat
+         ? LIBPKG_CONFIG_PKG_PKGF_SEARCH_PRIVATE |
+           LIBPKG_CONFIG_PKG_PKGF_ADD_PRIVATE_FRAGMENTS
+         : 0));
+
+      pkg_config_list_t f = LIBPKG_CONFIG_LIST_INITIALIZER; // Empty list.
+      int e (pkg_config_pkg_libs (client_, pkg_, &f, max_depth));
+
+      if (e != LIBPKG_CONFIG_PKG_ERRF_OK)
+        throw failed (); // Assume the diagnostics is issued.
+
+      unique_ptr<pkg_config_list_t, fragments_deleter> fd (&f);
+      return to_strings (f, 'L', client_->filter_libdirs);
+    }
+
+    optional<string> pkgconfig::
+    variable (const char* name) const
+    {
+      assert (client_ != nullptr); // Must not be empty.
+
+      const char* r (pkg_config_tuple_find (client_, &pkg_->vars, name));
+      return r != nullptr ? optional<string> (r) : nullopt;
+    }
+  }
+}
+
+#endif // BUILD2_BOOTSTRAP
diff --git a/libbuild2/cc/pkgconfig.hxx b/libbuild2/cc/pkgconfig.hxx
index 3ea9e2e..7959da1 100644
--- a/libbuild2/cc/pkgconfig.hxx
+++ b/libbuild2/cc/pkgconfig.hxx
@@ -9,7 +9,11 @@
 //
 #ifndef BUILD2_BOOTSTRAP
 
-#include <libpkgconf/libpkgconf.h>
+#ifndef BUILD2_LIBPKGCONF
+#  include <libpkg-config/pkg-config.h>
+#else
+#  include <libpkgconf/libpkgconf.h>
+#endif
 
 #include <libbuild2/types.hxx>
 #include <libbuild2/utility.hxx>
@@ -74,11 +78,13 @@ namespace build2
       void
       free ();
 
-      // Keep them as raw pointers not to deal with API thread-unsafety in
-      // deleters and introducing additional mutex locks.
-      //
+#ifndef BUILD2_LIBPKGCONF
+      pkg_config_client_t* client_ = nullptr;
+      pkg_config_pkg_t* pkg_ = nullptr;
+#else
       pkgconf_client_t* client_ = nullptr;
       pkgconf_pkg_t* pkg_ = nullptr;
+#endif
     };
 
     inline pkgconfig::