From 091de5764d73f9c084827afa154a691d7d9ac75a Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Fri, 4 Aug 2017 07:30:12 +0200
Subject: Add extracted from pkg-config prerequisite libraries as prerequisites

---
 build2/bin/target.cxx   |  2 +-
 build2/bin/target.hxx   |  8 ++++++--
 build2/cc/pkgconfig.cxx | 49 ++++++++++++++++++++++++++++++++-----------------
 3 files changed, 39 insertions(+), 20 deletions(-)

diff --git a/build2/bin/target.cxx b/build2/bin/target.cxx
index aa37202..d9dc64b 100644
--- a/build2/bin/target.cxx
+++ b/build2/bin/target.cxx
@@ -13,7 +13,7 @@ namespace build2
     const target_type libx::static_type
     {
       "libx",
-      &target::static_type,
+      &mtime_target::static_type,
       nullptr,
       nullptr,
       nullptr,
diff --git a/build2/bin/target.hxx b/build2/bin/target.hxx
index e0c0358..790d1f0 100644
--- a/build2/bin/target.hxx
+++ b/build2/bin/target.hxx
@@ -119,10 +119,14 @@ namespace build2
 
     // Common base for lib{} and libu{} groups.
     //
-    class libx: public target
+    // We use mtime_target as a base for the "trust me it exists" functionality
+    // which we use, for example, to have installed lib{} prerequisites that
+    // are matched by the fallback file rule.
+    //
+    class libx: public mtime_target
     {
     public:
-      using target::target;
+      using mtime_target::mtime_target;
 
     public:
       static const target_type static_type;
diff --git a/build2/cc/pkgconfig.cxx b/build2/cc/pkgconfig.cxx
index b83ad66..29abb57 100644
--- a/build2/cc/pkgconfig.cxx
+++ b/build2/cc/pkgconfig.cxx
@@ -283,10 +283,11 @@ namespace build2
         }
       };
 
-      // Parse --libs into loptions/libs (interface and implementation).
+      // Parse --libs into loptions/libs (interface and implementation). If
+      // ps is not NULL, add each resolves library target as a prerequisite.
       //
       auto parse_libs = [act, &s, sysd, &extract, &next, this]
-        (target& t, const path& f, bool a)
+        (target& t, const path& f, bool a, prerequisites* ps)
       {
         string lstr (extract (f, "--libs", a));
 
@@ -451,8 +452,7 @@ namespace build2
           prerequisite_key pk {
             nullopt, {&lib::static_type, &out, &out, &name, nullopt}, &s};
 
-          if (lib* lt = static_cast<lib*> (
-                search_library (act, sysd, usrd, pk)))
+          if (const target* lt = search_library (act, sysd, usrd, pk))
           {
             // We used to pick a member but that doesn't seem right since the
             // same target could be used with different link orders.
@@ -460,6 +460,9 @@ namespace build2
             n.dir = lt->dir;
             n.type = lib::static_type.name;
             n.value = lt->name;
+
+            if (ps != nullptr)
+              ps->push_back (prerequisite (*lt));
           }
           else
             // If we couldn't find the library, then leave it as -l.
@@ -517,15 +520,13 @@ namespace build2
         }
       };
 
-      // Parse modules and add them as prerequisites of the library target.
+      // Parse modules and add them to the prerequisites.
       //
       auto parse_modules = [&trace, &extract, &next, this]
-        (target& t, const path& f)
+        (const path& f, prerequisites& ps)
       {
         string mstr (extract (f, "--variable=modules", false));
 
-        prerequisites ps;
-
         string m;
         for (size_t b (0), e (0); !(m = next (mstr, b, e)).empty (); )
         {
@@ -563,29 +564,33 @@ namespace build2
 
           ps.push_back (prerequisite (mt));
         }
-
-        assert (!t.has_prerequisites ());
-        t.prerequisites (move (ps));
       };
 
-      pair<path, path> ps (search ());
-      const path& ap (ps.first);
-      const path& sp (ps.second);
+      pair<path, path> pp (search ());
+      const path& ap (pp.first);
+      const path& sp (pp.second);
 
       if (ap.empty () && sp.empty ())
         return false;
 
+      // For now we only populate prerequisites for lib{}. To do it for
+      // liba{} would require weeding out duplicates that are already in
+      // lib{}.
+      //
+      prerequisites ps;
+
       // First sort out the interface dependencies (which we are setting on
       // lib{}). If we have the shared .pc variant, then we use that.
       // Otherwise -- static but extract without the --static option (see also
       // the saving logic).
       //
-      parse_libs (lt, sp.empty () ? sp : ap, false);
+      const path& ip (sp.empty () ? ap : sp); // Interface path.
+      parse_libs (lt, ip, false, &ps);
 
       if (at != nullptr && !ap.empty ())
       {
         parse_cflags (*at, ap, true);
-        parse_libs (*at, ap, true);
+        parse_libs (*at, ap, true, nullptr);
       }
 
       if (st != nullptr && !sp.empty ())
@@ -597,7 +602,17 @@ namespace build2
       // libraries) and life is short.
       //
       if (modules)
-        parse_modules (lt, sp.empty () ? ap : sp);
+        parse_modules (ip, ps);
+
+      assert (!lt.has_prerequisites ());
+      if (!ps.empty ())
+        lt.prerequisites (move (ps));
+
+      // Bless the library group with a "trust me it exists" timestamp. Failed
+      // that, if we add it as a prerequisite (like we do above), the fallback
+      // file rule won't match.
+      //
+      lt.mtime (file_mtime (ip));
 
       return true;
     }
-- 
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