From 83b5af87efef571b707fc1f409f22571a9f5054c Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Fri, 12 Aug 2016 16:23:37 +0200
Subject: Add support for ordering modules in config.build

---
 build2/config/module        | 18 +++++++++++++++---
 build2/config/module.cxx    | 22 ++++++++++++++--------
 build2/config/operation.cxx |  7 +++----
 build2/config/utility       |  5 +++++
 build2/config/utility.cxx   | 10 ++++++++++
 5 files changed, 47 insertions(+), 15 deletions(-)

(limited to 'build2/config')

diff --git a/build2/config/module b/build2/config/module
index 7360cf6..21a7e28 100644
--- a/build2/config/module
+++ b/build2/config/module
@@ -5,6 +5,7 @@
 #ifndef BUILD2_CONFIG_MODULE
 #define BUILD2_CONFIG_MODULE
 
+#include <map>
 #include <algorithm> // find_if()
 
 #include <butl/prefix-map>
@@ -49,15 +50,26 @@ namespace build2
 
     struct saved_modules: butl::prefix_map<string, saved_variables, '.'>
     {
-      vector<const_iterator> sequence;
+      // Priority order with INT32_MIN being the highest. Modules with the
+      // same priority are saved in the order inserted.
+      //
+      // Generally, the idea is that we want higher-level modules at the top
+      // of the file since that's the configuration that we usualy want to
+      // change. So we have the following priority bands/defaults:
+      //
+      // 101-200/150 - code generators (e.g., yacc, bison)
+      // 201-300/250 - compilers (e.g., C, C++),
+      // 301-400/350 - binutils (ar, ld)
+      //
+      std::multimap<std::int32_t, const_iterator> order;
 
       iterator
-      insert (string name)
+      insert (string name, int prio = 0)
       {
         auto p (emplace (move (name), saved_variables ()));
 
         if (p.second)
-          sequence.push_back (p.first);
+          order.emplace (prio, p.first);
 
         return p.first;
       }
diff --git a/build2/config/module.cxx b/build2/config/module.cxx
index d4b9b49..de106b7 100644
--- a/build2/config/module.cxx
+++ b/build2/config/module.cxx
@@ -11,6 +11,7 @@
 #include <build2/filesystem> // file_exists()
 #include <build2/diagnostics>
 
+#include <build2/config/utility>
 #include <build2/config/operation>
 
 using namespace std;
@@ -23,17 +24,17 @@ namespace build2
     const string module::name ("config");
 
     void
-    boot (scope& root, const location&, unique_ptr<module_base>&)
+    boot (scope& rs, const location&, unique_ptr<module_base>&)
     {
       tracer trace ("config::boot");
 
-      const dir_path& out_root (root.out_path ());
+      const dir_path& out_root (rs.out_path ());
       l5 ([&]{trace << "for " << out_root;});
 
       // Register meta-operations.
       //
-      root.meta_operations.insert (configure_id, configure);
-      root.meta_operations.insert (disfigure_id, disfigure);
+      rs.meta_operations.insert (configure_id, configure);
+      rs.meta_operations.insert (disfigure_id, disfigure);
 
       // Load config.build if one exists.
       //
@@ -45,11 +46,11 @@ namespace build2
       path f (out_root / config_file);
 
       if (file_exists (f))
-        source (f, root, root);
+        source (f, rs, rs);
     }
 
     bool
-    init (scope& root,
+    init (scope& rs,
           scope&,
           const location& l,
           unique_ptr<module_base>& mod,
@@ -65,7 +66,7 @@ namespace build2
         return true;
       }
 
-      l5 ([&]{trace << "for " << root.out_path ();});
+      l5 ([&]{trace << "for " << rs.out_path ();});
 
       assert (config_hints.empty ()); // We don't known any hints.
 
@@ -74,6 +75,11 @@ namespace build2
       if (current_mif->id == configure_id)
         mod.reset (new module);
 
+      // Adjust priority for the import pseudo-module so that config.import.*
+      // values come first in config.build.
+      //
+      config::save_module (rs, "import", INT32_MIN);
+
       // Register alias and fallback rule for the configure meta-operation.
       //
       {
@@ -83,7 +89,7 @@ namespace build2
         global_scope->rules.insert<file> (
           configure_id, 0, "config.file", file_rule::instance);
 
-        auto& r (root.rules);
+        auto& r (rs.rules);
 
         r.insert<target> (configure_id, 0, "config", fallback_rule::instance);
         r.insert<file> (configure_id, 0, "config.file", fallback_rule::instance);
diff --git a/build2/config/operation.cxx b/build2/config/operation.cxx
index 89ddcfb..ca2d559 100644
--- a/build2/config/operation.cxx
+++ b/build2/config/operation.cxx
@@ -93,11 +93,10 @@ namespace build2
         //
         names storage;
 
-        for (const saved_modules::const_iterator& i:
-               mod.saved_modules.sequence)
+        for (auto p: mod.saved_modules.order)
         {
-          const string& sname (i->first);
-          const saved_variables& svars (i->second);
+          const string& sname (p.second->first);
+          const saved_variables& svars (p.second->second);
 
           bool first (true); // Separate modules with a blank line.
           for (const saved_variable& sv: svars)
diff --git a/build2/config/utility b/build2/config/utility
index 2be2842..d11a38b 100644
--- a/build2/config/utility
+++ b/build2/config/utility
@@ -132,6 +132,11 @@ namespace build2
 
     void
     save_variable (scope& root, const variable&, uint64_t flags = 0);
+
+    // Establish module order/priority. See config::module for details.
+    //
+    void
+    save_module (scope& root, const char* name, int prio = 0);
   }
 }
 
diff --git a/build2/config/utility.cxx b/build2/config/utility.cxx
index b73e852..45417f1 100644
--- a/build2/config/utility.cxx
+++ b/build2/config/utility.cxx
@@ -170,5 +170,15 @@ namespace build2
           assert (j->flags == flags);
       }
     }
+
+    void
+    save_module (scope& r, const char* name, int prio)
+    {
+      if (current_mif->id != configure_id)
+        return;
+
+      if (module* m = r.modules.lookup<module> (module::name))
+        m->saved_modules.insert (string ("config.") += name, prio);
+    }
   }
 }
-- 
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