Implement MSVC installation discovery for version 15 (2017) and later

In particular, this removes the requirement to build from the Visual Studio
command prompt. Note that since MSVC compiler binaries are target-specific
(i.e., there are no -m32/-m64 options nor something like /MACHINE), in this
case we default to a 64-bit build (a 32-bit build can still be achieved by
running from a suitable command prompt).

Finally, this mechanism is also used to find Clang bundled with MSVC.

1 files changed, 44 insertions, 81 deletions

diff --git a/libbuild2/cc/compile-rule.cxx b/libbuild2/cc/compile-rule.cxx
index d4ea390..9a534c7 100644
--- a/libbuild2/cc/compile-rule.cxx
+++ b/libbuild2/cc/compile-rule.cxx
@@ -186,6 +186,37 @@ namespace build2
                      "insufficient space");
     }
 
+    template <typename T>
+    void compile_rule::
+    append_sys_inc_options (T& args) const
+    {
+      assert (sys_inc_dirs_extra <= sys_inc_dirs.size ());
+
+      auto b (sys_inc_dirs.begin ());
+      auto m (b + sys_inc_dirs_extra);
+      auto e (sys_inc_dirs.end ());
+
+      append_option_values (
+        args, cclass == compiler_class::msvc ? "/I" : "-I",
+        m, e,
+        [] (const dir_path& d) {return d.string ().c_str ();});
+
+      // For MSVC if we have no INCLUDE environment variable set, then we
+      // add all of them. But we want extras to come first. Note also that
+      // clang-cl takes care of this itself.
+      //
+      if (ctype == compiler_type::msvc && cvariant != "clang")
+      {
+        if (!getenv ("INCLUDE"))
+        {
+          append_option_values (
+            args, "/I",
+            b, m,
+            [] (const dir_path& d) {return d.string ().c_str ();});
+        }
+      }
+    }
+
     size_t compile_rule::
     append_lang_options (cstrings& args, const match_data& md) const
     {
@@ -342,9 +373,10 @@ namespace build2
     // Append or hash library options from a pair of *.export.* variables
     // (first one is cc.export.*) recursively, prerequisite libraries first.
     //
+    template <typename T>
     void compile_rule::
     append_lib_options (const scope& bs,
-                        cstrings& args,
+                        T& args,
                         action a,
                         const target& t,
                         linfo li) const
@@ -402,59 +434,6 @@ namespace build2
       }
     }
 
-    void compile_rule::
-    hash_lib_options (const scope& bs,
-                      sha256& cs,
-                      action a,
-                      const target& t,
-                      linfo li) const
-    {
-      auto imp = [] (const file& l, bool la) {return la && l.is_a<libux> ();};
-
-      auto opt = [&cs, this] (
-        const file& l, const string& t, bool com, bool exp)
-      {
-        if (!exp)
-          return;
-
-        const variable& var (
-          com
-          ? c_export_poptions
-          : (t == x
-             ? x_export_poptions
-             : l.ctx.var_pool[t + ".export.poptions"]));
-
-        hash_options (cs, l, var);
-      };
-
-      // The same logic as in append_lib_options().
-      //
-      const function<bool (const file&, bool)> impf (imp);
-      const function<void (const file&, const string&, bool, bool)> optf (opt);
-
-      for (prerequisite_member p: group_prerequisite_members (a, t))
-      {
-        if (include (a, t, p) != include_type::normal) // Excluded/ad hoc.
-          continue;
-
-        if (const target* pt = p.load ())
-        {
-          if (const libx* l = pt->is_a<libx> ())
-            pt = link_member (*l, a, li);
-
-          bool la;
-          if (!((la = pt->is_a<liba> ())  ||
-                (la = pt->is_a<libux> ()) ||
-                pt->is_a<libs> ()))
-            continue;
-
-          process_libraries (a, bs, li, sys_lib_dirs,
-                             pt->as<file> (), la, 0, // Hack: lflags unused.
-                             impf, nullptr, optf);
-        }
-      }
-    }
-
     // Append library prefixes based on the *.export.poptions variables
     // recursively, prerequisite libraries first.
     //
@@ -877,29 +856,25 @@ namespace build2
             cs.append (&md.symexport, sizeof (md.symexport));
 
           if (xlate_hdr != nullptr)
-            hash_options (cs,  *xlate_hdr);
+            append_options (cs,  *xlate_hdr);
 
           if (md.pp != preprocessed::all)
           {
-            hash_options (cs, t, c_poptions);
-            hash_options (cs, t, x_poptions);
+            append_options (cs, t, c_poptions);
+            append_options (cs, t, x_poptions);
 
             // Hash *.export.poptions from prerequisite libraries.
             //
-            hash_lib_options (bs, cs, a, t, li);
+            append_lib_options (bs, cs, a, t, li);
 
             // Extra system header dirs (last).
             //
-            assert (sys_inc_dirs_extra <= sys_inc_dirs.size ());
-            hash_option_values (
-              cs, "-I",
-              sys_inc_dirs.begin () + sys_inc_dirs_extra, sys_inc_dirs.end (),
-              [] (const dir_path& d) {return d.string ();});
+            append_sys_inc_options (cs);
           }
 
-          hash_options (cs, t, c_coptions);
-          hash_options (cs, t, x_coptions);
-          hash_options (cs, tstd);
+          append_options (cs, t, c_coptions);
+          append_options (cs, t, x_coptions);
+          append_options (cs, tstd);
 
           if (ot == otype::s)
           {
@@ -2956,11 +2931,7 @@ namespace build2
 
           // Extra system header dirs (last).
           //
-          assert (sys_inc_dirs_extra <= sys_inc_dirs.size ());
-          append_option_values (
-            args, "-I",
-            sys_inc_dirs.begin () + sys_inc_dirs_extra, sys_inc_dirs.end (),
-            [] (const dir_path& d) {return d.string ().c_str ();});
+          append_sys_inc_options (args);
 
           if (md.symexport)
             append_symexport_options (args, t);
@@ -4098,11 +4069,7 @@ namespace build2
 
           append_lib_options (t.base_scope (), args, a, t, li);
 
-          assert (sys_inc_dirs_extra <= sys_inc_dirs.size ());
-          append_option_values (
-            args, "-I",
-            sys_inc_dirs.begin () + sys_inc_dirs_extra, sys_inc_dirs.end (),
-            [] (const dir_path& d) {return d.string ().c_str ();});
+          append_sys_inc_options (args);
 
           if (md.symexport)
             append_symexport_options (args, t);
@@ -5693,11 +5660,7 @@ namespace build2
 
         // Extra system header dirs (last).
         //
-        assert (sys_inc_dirs_extra <= sys_inc_dirs.size ());
-        append_option_values (
-          args, "-I",
-          sys_inc_dirs.begin () + sys_inc_dirs_extra, sys_inc_dirs.end (),
-          [] (const dir_path& d) {return d.string ().c_str ();});
+        append_sys_inc_options (args);
 
         if (md.symexport)
           append_symexport_options (args, t);