From 55ddc71fd801e06115ad6e33098b0eed2517daab Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 5 Nov 2019 13:16:21 +0200
Subject: Add support for automatic importing of libbuild2 of installed case

---
 libbuild2/buildfile               | 10 ++++++++++
 libbuild2/cc/common.cxx           | 17 ++++++++++++++++-
 libbuild2/file.cxx                |  3 +++
 libbuild2/utility-installed.cxx   |  4 ++++
 libbuild2/utility-uninstalled.cxx |  1 +
 libbuild2/utility.hxx             |  4 +++-
 6 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/libbuild2/buildfile b/libbuild2/buildfile
index 325d54a..545ccba 100644
--- a/libbuild2/buildfile
+++ b/libbuild2/buildfile
@@ -117,9 +117,19 @@ cross = ($cxx.target.cpu != $build.host.cpu || \
          $cxx.target.system != $build.host.system)
 
 if! $cross
+{
   {obja objs}{context}: cxx.poptions += \
     -DBUILD2_IMPORT_PATH=\"$regex.replace($out_root, '\\', '\\\\')\"
 
+  # While this object file should only be linked when we are installing, it
+  # will be compiled even in the uninstalled case.
+  #
+  if ($install.root != [null])
+    {obja objs}{utility-installed}: cxx.poptions += \
+      -DBUILD2_INSTALL_LIB=\"$regex.replace(\
+        $install.resolve($install.lib), '\\', '\\\\')\"
+}
+
 if ($cxx.target.class != 'windows')
 {
   libul{build2}: cxx.libs += -lpthread
diff --git a/libbuild2/cc/common.cxx b/libbuild2/cc/common.cxx
index f14f973..587ae08 100644
--- a/libbuild2/cc/common.cxx
+++ b/libbuild2/cc/common.cxx
@@ -786,13 +786,28 @@ namespace build2
         return a != nullptr || s != nullptr;
       };
 
-      // First try user directories (i.e., -L).
+      // First try user directories (i.e., -L or /LIBPATH).
       //
       bool sys (false);
 
       if (!usrd)
+      {
         usrd = extract_library_dirs (*p.scope);
 
+        // Handle automatic importing of installed build2 libraries. This is a
+        // mirror side of the uninstalled case that is handled via the special
+        // import.build2 value in import_search().
+        //
+        if (build_installed && p.proj && *p.proj == "build2")
+        {
+          // Note that we prepend it to other user directories instead of
+          // making it the only one to allow things to be overriden (e.g., if
+          // build2 was moved or some such).
+          //
+          usrd->insert (usrd->begin (), build_install_lib);
+        }
+      }
+
       const dir_path* pd (nullptr);
       for (const dir_path& d: *usrd)
       {
diff --git a/libbuild2/file.cxx b/libbuild2/file.cxx
index b55d576..974dc2b 100644
--- a/libbuild2/file.cxx
+++ b/libbuild2/file.cxx
@@ -1435,6 +1435,9 @@ namespace build2
 
       // import.build2
       //
+      // Note that the installed case is taken care of by special code in the
+      // cc module's search_library().
+      //
       if (proj == "build2")
       {
         // Note that this variable can be set to NULL to disable relying on
diff --git a/libbuild2/utility-installed.cxx b/libbuild2/utility-installed.cxx
index c8f08b6..29c822b 100644
--- a/libbuild2/utility-installed.cxx
+++ b/libbuild2/utility-installed.cxx
@@ -11,6 +11,10 @@
 namespace build2
 {
   const bool build_installed = true;
+
+#ifdef BUILD2_INSTALL_LIB
+  const dir_path build_install_lib (BUILD2_INSTALL_LIB);
+#endif
 }
 
 #endif
diff --git a/libbuild2/utility-uninstalled.cxx b/libbuild2/utility-uninstalled.cxx
index 0006e1a..dc56244 100644
--- a/libbuild2/utility-uninstalled.cxx
+++ b/libbuild2/utility-uninstalled.cxx
@@ -7,4 +7,5 @@
 namespace build2
 {
   const bool build_installed = false;
+  const dir_path build_install_lib; // Empty.
 }
diff --git a/libbuild2/utility.hxx b/libbuild2/utility.hxx
index 415dc8b..8cd33cf 100644
--- a/libbuild2/utility.hxx
+++ b/libbuild2/utility.hxx
@@ -160,9 +160,11 @@ namespace build2
   LIBBUILD2_SYMEXPORT extern const standard_version build_version;
   LIBBUILD2_SYMEXPORT extern const string build_version_interface;
 
-  // Whether running installed build.
+  // Whether running installed build and, if so, the library installation
+  // directory (empty otherwise).
   //
   LIBBUILD2_SYMEXPORT extern const bool build_installed;
+  LIBBUILD2_SYMEXPORT extern const dir_path build_install_lib; // $install.lib
 
   // --[no-]mtime-check
   //
-- 
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