Generate common .pc file in addition to static/staged when installing lib{}

The common .pc file is produced by ignoring any static/shared-specific
poptions and splitting loptions/libs into Libs/Libs.private.

It is "best effort", in a sense that it's not guaranteed to be sufficient in
all cases, but it will probably cover the majority of cases, even on Windows,
thanks to automatic dllimport'ing of functions.

6 files changed, 88 insertions, 26 deletions

diff --git a/libbuild2/cc/link-rule.cxx b/libbuild2/cc/link-rule.cxx
index 6047206..b11ee42 100644
--- a/libbuild2/cc/link-rule.cxx
+++ b/libbuild2/cc/link-rule.cxx
@@ -17,6 +17,7 @@
 #include <libbuild2/filesystem.hxx>
 #include <libbuild2/diagnostics.hxx>
 
+#include <libbuild2/bin/rule.hxx>    // lib_rule::build_members()
 #include <libbuild2/bin/target.hxx>
 #include <libbuild2/bin/utility.hxx>
 
@@ -125,7 +126,7 @@ namespace build2
             // doing here since if there is no existing target, then there can
             // be no prerequisites.
             //
-            // Note, however, that we cannot linkup a prerequisite target
+            // Note, however, that we cannot link-up a prerequisite target
             // member to its group since we are not matching this target. As
             // result we have to do all the steps except for setting t.group
             // and pass both member and group (we also cannot query t.group
@@ -1029,21 +1030,41 @@ namespace build2
           // cleanup automagically. The actual generation happens in
           // perform_update() below.
           //
+          // Things are even trickier for the common .pc file: we only want to
+          // have it in the shared library if we are not installing static
+          // (see pkgconfig_save() for details). But we can't know it at this
+          // stage. So what we are going to do is conceptually tie the common
+          // file to the lib{} group (which does somehow feel correct) by only
+          // installing it if the lib{} group is installed. Specifically, here
+          // we will use its bin.lib to decide what will be installed and in
+          // perform_update() we will confirm that it is actually installed.
+          //
           if (ot != otype::e)
           {
-            file& pc (add_adhoc_member<file> (t,
-                                              (ot == otype::a
-                                               ? pca::static_type
-                                               : pcs::static_type)));
-
             // Note that here we always use the lib name prefix, even on
             // Windows with VC. The reason is the user needs a consistent name
             // across platforms by which they can refer to the library. This
             // is also the reason why we use the .static and .shared second-
             // level extensions rather that a./.lib and .so/.dylib/.dll.
+
+            // Note also that the order in which we are adding these members
+            // is important (see add_addhoc_member() for details).
             //
-            if (pc.path ().empty ())
-              pc.derive_path (nullptr, (p == nullptr ? "lib" : p), s);
+            if (ot == otype::a || !lib_rule::build_members (rs).a)
+            {
+              auto& pc (add_adhoc_member<pc> (t));
+
+              if (pc.path ().empty ())
+                pc.derive_path (nullptr, (p == nullptr ? "lib" : p), s);
+            }
+
+            auto& pcx (add_adhoc_member<file> (t,
+                                               (ot == otype::a
+                                                ? pca::static_type
+                                                : pcs::static_type)));
+
+            if (pcx.path ().empty ())
+              pcx.derive_path (nullptr, (p == nullptr ? "lib" : p), s);
           }
 
           // Add the Windows rpath emulating assembly directory as fsdir{}.
@@ -1984,7 +2005,26 @@ namespace build2
       // for install, we have no idea where-to things will be installed.
       //
       if (for_install && lt.library () && !lt.utility)
-        pkgconfig_save (a, t, lt.static_library (), binless);
+      {
+        bool la (lt.static_library ());
+
+        pkgconfig_save (a, t, la, false /* common */, binless);
+
+        // Generate the common .pc file if the lib{} rule is matched (see
+        // apply() for details on this two-stage logic).
+        //
+        auto* m (find_adhoc_member<pc> (t)); // Will be pca/pcs if not found.
+
+        if (!m->is_a (la ? pca::static_type : pcs::static_type))
+        {
+          if (t.group->matched (a))
+            pkgconfig_save (a, t, la, true /* common */, binless);
+          else
+            // Mark as non-existent not to confuse the install rule.
+            //
+            m->mtime (timestamp_nonexistent);
+        }
+      }
 
       // If we have no binary to build then we are done.
       //
diff --git a/libbuild2/cc/link-rule.hxx b/libbuild2/cc/link-rule.hxx
index 6fa8343..ce514b5 100644
--- a/libbuild2/cc/link-rule.hxx
+++ b/libbuild2/cc/link-rule.hxx
@@ -178,7 +178,7 @@ namespace build2
       // pkg-config's .pc file generation (pkgconfig.cxx).
       //
       void
-      pkgconfig_save (action, const file&, bool, bool) const;
+      pkgconfig_save (action, const file&, bool, bool, bool) const;
 
     private:
       const string rule_id;
diff --git a/libbuild2/cc/module.cxx b/libbuild2/cc/module.cxx
index 70cbc47..d6c337d 100644
--- a/libbuild2/cc/module.cxx
+++ b/libbuild2/cc/module.cxx
@@ -776,6 +776,7 @@ namespace build2
         if (*x_hdr != &h::static_type)
           insert_hdr (h::static_type);
 
+        rs.insert_target_type<pc> ();
         rs.insert_target_type<pca> ();
         rs.insert_target_type<pcs> ();
 
diff --git a/libbuild2/cc/pkgconfig.cxx b/libbuild2/cc/pkgconfig.cxx
index 64dd9ca..f95599f 100644
--- a/libbuild2/cc/pkgconfig.cxx
+++ b/libbuild2/cc/pkgconfig.cxx
@@ -1301,8 +1301,19 @@ namespace build2
 
 #endif
 
+    // If common is true, generate a "best effort" (i.e., not guaranteed to be
+    // sufficient in all cases) common .pc file by ignoring any static/shared-
+    // specific poptions and splitting loptions/libs into Libs/Libs.private.
+    // Note that if both static and shared are being installed, the common
+    // file must be generated based on the static library to get accurate
+    // Libs.private.
+    //
     void link_rule::
-    pkgconfig_save (action a, const file& l, bool la, bool binless) const
+    pkgconfig_save (action a,
+                    const file& l,
+                    bool la,
+                    bool common,
+                    bool binless) const
     {
       tracer trace (x, "pkgconfig_save");
 
@@ -1311,15 +1322,22 @@ namespace build2
       const scope& bs (l.base_scope ());
       const scope& rs (*bs.root_scope ());
 
-      auto* t (find_adhoc_member<pc> (l));
+      auto* t (find_adhoc_member<pc> (l, (common ? pc::static_type  :
+                                          la     ? pca::static_type :
+                                          /*    */ pcs::static_type)));
       assert (t != nullptr);
 
+      // This is the lib{} group if we are generating the common file and the
+      // target itself otherwise.
+      //
+      const file& g (common ? l.group->as<file> () : l);
+
       // By default we assume things go into install.{include, lib}.
       //
       using install::resolve_dir;
 
-      dir_path idir (resolve_dir (l, cast<dir_path> (l["install.include"])));
-      dir_path ldir (resolve_dir (l, cast<dir_path> (l["install.lib"])));
+      dir_path idir (resolve_dir (g, cast<dir_path> (g["install.include"])));
+      dir_path ldir (resolve_dir (g, cast<dir_path> (g["install.lib"])));
 
       const path& p (t->path ());
 
@@ -1363,9 +1381,9 @@ namespace build2
             os << "URL: " << *u << endl;
         }
 
-        auto save_poptions = [&l, &os] (const variable& var)
+        auto save_poptions = [&g, &os] (const variable& var)
         {
-          if (const strings* v = cast_null<strings> (l[var]))
+          if (const strings* v = cast_null<strings> (g[var]))
           {
             for (auto i (v->begin ()); i != v->end (); ++i)
             {
@@ -1469,11 +1487,11 @@ namespace build2
         // we still want to sort things out into Libs/Libs.private. This is
         // necessary to distinguish between interface and implementation
         // dependencies if we don't have the shared variant (see the load
-        // logic for details).
+        // logic for details). And also for the common .pc file, naturally.
         //
         //@@ TODO: would be nice to weed out duplicates. But is it always
         //   safe? Think linking archives: will have to keep duplicates in
-        //   the second position, not first. Gets even trickier with
+        //   the second position, not first. Gets even trickier with the
         //   Libs.private split.
         //
         {
@@ -1556,7 +1574,7 @@ namespace build2
           };
           vector<module> modules;
 
-          for (const target* pt: l.prerequisite_targets[a])
+          for (const target* pt: g.prerequisite_targets[a])
           {
             // @@ UTL: we need to (recursively) see through libu*{} (and
             //    also in search_modules()).
diff --git a/libbuild2/cc/target.cxx b/libbuild2/cc/target.cxx
index a962575..b17e1ef 100644
--- a/libbuild2/cc/target.cxx
+++ b/libbuild2/cc/target.cxx
@@ -54,16 +54,18 @@ namespace build2
       false
     };
 
+    extern const char pc_ext[] = "pc"; // VC14 rejects constexpr.
+
     const target_type pc::static_type
     {
       "pc",
       &file::static_type,
-      nullptr,
-      nullptr,
-      nullptr,
-      nullptr,
-      nullptr,
-      &target_search,
+      &target_factory<pc>,
+      &target_extension_fix<pc_ext>,
+      nullptr, /* default_extension */
+      &target_pattern_fix<pc_ext>,
+      &target_print_0_ext_verb, // Fixed extension, no use printing.
+      &file_search,
       false
     };
 
diff --git a/libbuild2/cc/target.hxx b/libbuild2/cc/target.hxx
index 42d15c8..7067421 100644
--- a/libbuild2/cc/target.hxx
+++ b/libbuild2/cc/target.hxx
@@ -61,13 +61,14 @@ namespace build2
 
     // pkg-config file targets.
     //
-    class LIBBUILD2_CC_SYMEXPORT pc: public file
+    class LIBBUILD2_CC_SYMEXPORT pc: public file // .pc (common)
     {
     public:
       using file::file;
 
     public:
       static const target_type static_type;
+      virtual const target_type& dynamic_type () const {return static_type;}
     };
 
     class LIBBUILD2_CC_SYMEXPORT pca: public pc // .static.pc