From 0b672184ef920d2581a0be43d27c25690ee0569d Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 23 May 2022 14:40:07 +0200
Subject: Cache build.host value in context

---
 libbuild2/build/script/script.cxx     | 2 +-
 libbuild2/context.cxx                 | 5 +++--
 libbuild2/context.hxx                 | 4 ++++
 libbuild2/install/rule.cxx            | 4 ++--
 libbuild2/test/init.cxx               | 2 +-
 libbuild2/test/script/parser.test.cxx | 2 +-
 6 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/libbuild2/build/script/script.cxx b/libbuild2/build/script/script.cxx
index b230ca5..a557065 100644
--- a/libbuild2/build/script/script.cxx
+++ b/libbuild2/build/script/script.cxx
@@ -32,7 +32,7 @@ namespace build2
                    const optional<timestamp>& dl)
           : build2::script::environment (
               t.ctx,
-              cast<target_triplet> (t.ctx.global_scope["build.host"]),
+              *t.ctx.build_host,
               dir_name_view (&work, &wd_name),
               temp_dir.path, false /* temp_dir_keep */,
               redirect (redirect_type::none),
diff --git a/libbuild2/context.cxx b/libbuild2/context.cxx
index 7b465b4..a7df959 100644
--- a/libbuild2/context.cxx
+++ b/libbuild2/context.cxx
@@ -134,11 +134,12 @@ namespace build2
       // Any variable assigned on the global scope should natually have the
       // global visibility.
       //
-      auto set = [&gs, &vp] (const char* var, auto val)
+      auto set = [&gs, &vp] (const char* var, auto val) -> const value&
       {
         using T = decltype (val);
         value& v (gs.assign (vp.insert<T> (var, variable_visibility::global)));
         v = move (val);
+        return v;
       };
 
       // Build system mode.
@@ -268,7 +269,7 @@ namespace build2
         set ("build.host.version", t.version);
         set ("build.host.class",   t.class_);
 
-        set ("build.host", move (t));
+        build_host = &set ("build.host", move (t)).as<target_triplet> ();
       }
       catch (const invalid_argument& e)
       {
diff --git a/libbuild2/context.hxx b/libbuild2/context.hxx
index 6eb85f7..ad7fdff 100644
--- a/libbuild2/context.hxx
+++ b/libbuild2/context.hxx
@@ -390,6 +390,10 @@ namespace build2
     variable_override_cache& global_override_cache;
     const strings& global_var_overrides;
 
+    // Cached values (from global scope).
+    //
+    const target_triplet* build_host; // build.host
+
     // Cached variables.
     //
 
diff --git a/libbuild2/install/rule.cxx b/libbuild2/install/rule.cxx
index 1411143..6458a54 100644
--- a/libbuild2/install/rule.cxx
+++ b/libbuild2/install/rule.cxx
@@ -811,7 +811,7 @@ namespace build2
       cstrings args;
 
       string reld (
-        cast<string> (ctx.global_scope["build.host.class"]) == "windows"
+        ctx.build_host->class_ == "windows"
         ? msys_path (chd)
         : relative (chd).string ());
 
@@ -857,7 +857,7 @@ namespace build2
       dir_path chd (chroot_path (rs, base.dir));
 
       string reld (
-        cast<string> (ctx.global_scope["build.host.class"]) == "windows"
+        ctx.build_host->class_ == "windows"
         ? msys_path (chd)
         : relative (chd).string ());
 
diff --git a/libbuild2/test/init.cxx b/libbuild2/test/init.cxx
index 539cdec..c2fc831 100644
--- a/libbuild2/test/init.cxx
+++ b/libbuild2/test/init.cxx
@@ -125,7 +125,7 @@ namespace build2
         value& v (rs.assign (d.test_target));
 
         if (!v || v.empty ())
-          v = cast<target_triplet> (rs.ctx.global_scope["build.host"]);
+          v = *rs.ctx.build_host;
       }
 
       extra.set_module (new module (move (d)));
diff --git a/libbuild2/test/script/parser.test.cxx b/libbuild2/test/script/parser.test.cxx
index e0dd3d2..ccd4104 100644
--- a/libbuild2/test/script/parser.test.cxx
+++ b/libbuild2/test/script/parser.test.cxx
@@ -218,7 +218,7 @@ namespace build2
             tt.assign (
               ctx.var_pool.rw ().insert<target_triplet> ("test.target")));
 
-          v = cast<target_triplet> (ctx.global_scope["build.host"]);
+          v = *ctx.build_host;
 
           testscript& st (
             ctx.targets.insert<testscript> (work,
-- 
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