Rework C/C++ standard translation in preparation for experimental/modules

Also fix bug in clang-apple versioning.

9 files changed, 232 insertions, 191 deletions

diff --git a/build2/c/init.cxx b/build2/c/init.cxx
index ada8596..998bc40 100644
--- a/build2/c/init.cxx
+++ b/build2/c/init.cxx
@@ -20,6 +20,7 @@ namespace build2
 {
   namespace c
   {
+    using cc::compiler_id;
     using cc::compiler_info;
 
     class config_module: public cc::config_module
@@ -29,64 +30,77 @@ namespace build2
       config_module (config_data&& d)
           : config_data (move (d)), cc::config_module (move (d)) {}
 
-      string
+      strings
       translate_std (const compiler_info&,
                      scope&,
-                     const string&) const override;
+                     const string*) const override;
     };
 
     using cc::module;
 
-    string config_module::
-    translate_std (const compiler_info& ci, scope& rs, const string& v) const
+    strings config_module::
+    translate_std (const compiler_info& ci, scope& rs, const string* v) const
     {
-      string r;
+      strings r;
 
-      if (ci.id.type == "msvc")
+      switch (ci.id.value ())
       {
-        // Standard-wise, with VC you get what you get. The question is
-        // whether we should verify that the requested standard is provided by
-        // this VC version. And if so, from which version should we say VC
-        // supports 90, 99, and 11? We should probably be as loose as possible
-        // here since the author will always be able to tighten (but not
-        // loosen) this in the buildfile (i.e., detect unsupported versions).
-        //
-        // The state of affairs seem to be (from Herb Sutter's blog):
-        //
-        // 10.0 - most of C95 plus a few C99 features
-        // 11.0 - partial support for the C++11 subset of C11
-        // 12.0 - more C11 features from the C++11 subset, most of C99
-        //
-        // So let's say C99 is supported from 10.0 and C11 from 11.0. And C90
-        // is supported by everything we care to support.
-        //
-        if (v != "90")
+      case compiler_id::msvc:
         {
-          uint64_t cver (ci.version.major);
-
-          if ((v == "99" && cver < 16) || // Since VS2010/10.0.
-              (v == "11" && cver < 17))   // Since VS2012/11.0.
+          // Standard-wise, with VC you get what you get. The question is
+          // whether we should verify that the requested standard is provided
+          // by this VC version. And if so, from which version should we say
+          // VC supports 90, 99, and 11? We should probably be as loose as
+          // possible here since the author will always be able to tighten
+          // (but not loosen) this in the buildfile (i.e., detect unsupported
+          // versions).
+          //
+          // The state of affairs seem to be (from Herb Sutter's blog):
+          //
+          // 10.0 - most of C95 plus a few C99 features
+          // 11.0 - partial support for the C++11 subset of C11
+          // 12.0 - more C11 features from the C++11 subset, most of C99
+          //
+          // So let's say C99 is supported from 10.0 and C11 from 11.0. And
+          // C90 is supported by everything we care to support.
+          //
+          if (v == nullptr)
+            ;
+          else if (*v != "90")
           {
-            fail << "C" << v << " is not supported by " << ci.signature <<
-              info << "required by " << project (rs) << '@' << rs.out_path ();
+            uint64_t cver (ci.version.major);
+
+            if ((*v == "99" && cver < 16) || // Since VS2010/10.0.
+                (*v == "11" && cver < 17))   // Since VS2012/11.0.
+            {
+              fail << "C" << *v << " is not supported by " << ci.signature <<
+                info << "required by " << project (rs) << '@' << rs.out_path ();
+            }
           }
+          break;
+        }
+      case compiler_id::gcc:
+      case compiler_id::clang:
+      case compiler_id::icc:
+        {
+          // 90 and 89 are the same standard. Translate 99 to 9x and 11 to 1x
+          // for compatibility with older versions of the compilers.
+          //
+          if (v == nullptr)
+            ;
+          else
+          {
+            string o ("-std=");
+
+            if      (*v == "90") o += "c90";
+            else if (*v == "99") o += "c9x";
+            else if (*v == "11") o += "c1x";
+            else o += *v; // In case the user specifies e.g., 'gnu11'.
+
+            r.push_back (move (o));
+          }
+          break;
         }
-      }
-      else
-      {
-        // 90 and 89 are the same standard. Translate 99 to 9x and 11 to 1x
-        // for compatibility with older versions of the compilers.
-        //
-        r = "-std=";
-
-        if (v == "90")
-          r += "c90";
-        else if (v == "99")
-          r += "c9x";
-        else if (v == "11")
-          r += "c1x";
-        else
-          r += v; // In case the user specifies something like 'gnu11'.
       }
 
       return r;
diff --git a/build2/cc/common.hxx b/build2/cc/common.hxx
index 55e6675..fa6ec5a 100644
--- a/build2/cc/common.hxx
+++ b/build2/cc/common.hxx
@@ -112,7 +112,7 @@ namespace build2
       const string& tsys;          // x.target.system
       const string& tclass;        // x.target.class
 
-      const string& tstd;          // Translated x_std value (can be empty).
+      const strings& tstd;         // Translated x_std value (options).
 
       const process_path* pkgconfig; // pkgconfig.path (can be NULL).
       const dir_paths& sys_lib_dirs; // x.sys_lib_dirs
@@ -153,7 +153,7 @@ namespace build2
             uint64_t mj, uint64_t mi,
             const process_path& path,
             const target_triplet& tg,
-            const string& std,
+            const strings& std,
             const process_path* pkgc,
             const dir_paths& sld,
             const dir_paths& sid,
@@ -177,22 +177,6 @@ namespace build2
     public:
       common (data&& d): data (move (d)) {}
 
-      // Language standard (x.std) mapping.
-      //
-      void
-      append_std (cstrings& args) const
-      {
-        if (!tstd.empty ())
-          args.push_back (tstd.c_str ());
-      }
-
-      void
-      hash_std (sha256& cs) const
-      {
-        if (!tstd.empty ())
-          cs.append (tstd);
-      }
-
       // Library handling.
       //
     public:
diff --git a/build2/cc/compile.cxx b/build2/cc/compile.cxx
index 5a95169..ce96e00 100644
--- a/build2/cc/compile.cxx
+++ b/build2/cc/compile.cxx
@@ -531,7 +531,7 @@ namespace build2
 
         hash_options (cs, t, c_coptions);
         hash_options (cs, t, x_coptions);
-        hash_std (cs);
+        hash_options (cs, tstd);
 
         if (ct == otype::s)
         {
@@ -1183,8 +1183,7 @@ namespace build2
           //
           append_options (args, t, c_coptions);
           append_options (args, t, x_coptions);
-
-          append_std (args);
+          append_options (args, tstd);
 
           if (cid == compiler_id::msvc)
           {
@@ -2057,8 +2056,7 @@ namespace build2
           //
           append_options (args, t, c_coptions);
           append_options (args, t, x_coptions);
-
-          append_std (args);
+          append_options (args, tstd);
 
           if (cid == compiler_id::msvc)
           {
@@ -2272,11 +2270,10 @@ namespace build2
 
       append_options (args, t, c_coptions);
       append_options (args, t, x_coptions);
+      append_options (args, tstd);
 
       string out, out1; // Storage.
 
-      append_std (args);
-
       if (cid == compiler_id::msvc)
       {
         // The /F*: option variants with separate names only became available
diff --git a/build2/cc/gcc.cxx b/build2/cc/gcc.cxx
index b5dd236..7f52a91 100644
--- a/build2/cc/gcc.cxx
+++ b/build2/cc/gcc.cxx
@@ -38,7 +38,7 @@ namespace build2
       args.push_back (xc.recall_string ());
       append_options (args, rs, c_coptions);
       append_options (args, rs, x_coptions);
-      if (!tstd.empty ()) args.push_back (tstd.c_str ());
+      append_options (args, tstd);
       append_options (args, rs, c_loptions);
       append_options (args, rs, x_loptions);
       args.push_back ("-print-search-dirs");
diff --git a/build2/cc/guess.cxx b/build2/cc/guess.cxx
index 9f14661..7dde013 100644
--- a/build2/cc/guess.cxx
+++ b/build2/cc/guess.cxx
@@ -1096,28 +1096,33 @@ namespace build2
       compiler_info r;
       const compiler_id& id (gr.id);
 
-      if (id.type == "gcc")
+      switch (id.value ())
       {
-        assert (id.variant.empty ());
-        r = guess_gcc (xl, xc, c_coptions, x_coptions, move (gr));
-      }
-      else if (id.type == "clang")
-      {
-        assert (id.variant.empty () || id.variant == "apple");
-        r = guess_clang (xl, xc, c_coptions, x_coptions, move (gr));
-      }
-      else if (id.type == "icc")
-      {
-        assert (id.variant.empty ());
-        r = guess_icc (xl, xc, c_coptions, x_coptions, move (gr));
-      }
-      else if (id.type == "msvc")
-      {
-        assert (id.variant.empty ());
-        r = guess_msvc (xl, xc, c_coptions, x_coptions, move (gr));
+      case compiler_id::gcc:
+        {
+          assert (id.variant.empty ());
+          r = guess_gcc (xl, xc, c_coptions, x_coptions, move (gr));
+          break;
+        }
+      case compiler_id::clang:
+        {
+          assert (id.variant.empty () || id.variant == "apple");
+          r = guess_clang (xl, xc, c_coptions, x_coptions, move (gr));
+          break;
+        }
+      case compiler_id::msvc:
+        {
+          assert (id.variant.empty ());
+          r = guess_msvc (xl, xc, c_coptions, x_coptions, move (gr));
+          break;
+        }
+      case compiler_id::icc:
+        {
+          assert (id.variant.empty ());
+          r = guess_icc (xl, xc, c_coptions, x_coptions, move (gr));
+          break;
+        }
       }
-      else
-        assert (false);
 
       // Derive binutils pattern unless this has already been done by the
       // compiler-specific code.
diff --git a/build2/cc/link.cxx b/build2/cc/link.cxx
index 91c2739..5c75d34 100644
--- a/build2/cc/link.cxx
+++ b/build2/cc/link.cxx
@@ -1192,7 +1192,7 @@ namespace build2
         {
           append_options (args, t, c_coptions);
           append_options (args, t, x_coptions);
-          append_std (args);
+          append_options (args, tstd);
         }
 
         append_options (args, t, c_loptions);
diff --git a/build2/cc/module.cxx b/build2/cc/module.cxx
index 885d6c7..cdc45e5 100644
--- a/build2/cc/module.cxx
+++ b/build2/cc/module.cxx
@@ -118,10 +118,9 @@ namespace build2
         }
       }
 
-      // Translate x_std value (if any) to the compiler option (if any).
+      // Translate x_std value (if any) to the compiler option(s) (if any).
       //
-      if (auto l = rs[x_std])
-        tstd = translate_std (ci, rs, cast<string> (*l));
+      tstd = translate_std (ci, rs, cast_null<string> (rs[x_std]));
 
       // Extract system library search paths from the compiler and determine
       // additional system include search paths.
@@ -129,7 +128,7 @@ namespace build2
       dir_paths lib_dirs;
       dir_paths inc_dirs;
 
-      if (ci.id.type == "msvc")
+      if (ci.id.value () == compiler_id::msvc)
         lib_dirs = msvc_library_search_paths (ci.path, rs);
       else
       {
@@ -188,7 +187,9 @@ namespace build2
 
         if (!tstd.empty ())
         {
-          dr << "  std        " << tstd << '\n';
+          dr << "  std       "; // One less space.
+          for (const string& o: tstd) dr << ' ' << o;
+          dr << '\n';
         }
 
         if (!ci.cc_pattern.empty ()) // bin_pattern printed by bin
diff --git a/build2/cc/module.hxx b/build2/cc/module.hxx
index eaa82eb..db17998 100644
--- a/build2/cc/module.hxx
+++ b/build2/cc/module.hxx
@@ -32,13 +32,14 @@ namespace build2
       void
       init (scope&, const location&, const variable_map&);
 
-      // Translate the x.std value to the standard-selecting option if there
-      // is any.
+      // Translate the x.std value (if any) to the standard-selecting
+      // option(s) (if any). May also check/set x.features.* variables on the
+      // root scope.
       //
-      virtual string
-      translate_std (const compiler_info&, scope&, const string&) const = 0;
+      virtual strings
+      translate_std (const compiler_info&, scope&, const string*) const = 0;
 
-      string tstd;
+      strings tstd;
 
       compiler_id::value_type cid;
 
diff --git a/build2/cxx/init.cxx b/build2/cxx/init.cxx
index 72a8fe5..a8706a3 100644
--- a/build2/cxx/init.cxx
+++ b/build2/cxx/init.cxx
@@ -20,6 +20,7 @@ namespace build2
 {
   namespace cxx
   {
+    using cc::compiler_id;
     using cc::compiler_info;
 
     class config_module: public cc::config_module
@@ -29,128 +30,166 @@ namespace build2
       config_module (config_data&& d)
           : config_data (move (d)), cc::config_module (move (d)) {}
 
-      string
+      strings
       translate_std (const compiler_info&,
                      scope&,
-                     const string&) const override;
+                     const string*) const override;
     };
 
     using cc::module;
 
-    string config_module::
-    translate_std (const compiler_info& ci, scope& rs, const string& v) const
+    strings config_module::
+    translate_std (const compiler_info& ci, scope& rs, const string* v) const
     {
-      string r;
+      strings r;
 
-      const string& t (ci.id.type);
+      auto id (ci.id.value ());
       uint64_t mj (ci.version.major);
       uint64_t mi (ci.version.minor);
       uint64_t p (ci.version.patch);
 
       // Translate "latest" to the compiler/version-appropriate option.
       //
-      if (v == "latest")
+      if (v != nullptr && *v == "latest")
       {
-        if (t == "msvc")
-        {
-          // VC14u3 and later has /std:c++latest.
-          //
-          if (mj > 19 || (mj == 19 && (mi > 0 || (mi == 0 && p >= 24215))))
-            r = "/std:c++latest";
-        }
-        else if (t == "gcc")
-        {
-          if      (mj >= 5)            r = "-std=c++1z"; // 17
-          else if (mj == 4 && mi >= 8) r = "-std=c++1y"; // 14
-          else if (mj == 4 && mi >= 4) r = "-std=c++0x"; // 11
-        }
-        else if (t == "clang")
-        {
-          if       (mj >  3 || (mj == 3 && mi >= 5)) r = "-std=c++1z"; // 17
-          else if  (mj == 3 && mi >= 4)              r = "-std=c++1y"; // 14
-          else    /* ??? */                          r = "-std=c++0x"; // 11
-        }
-        else if (t == "icc")
+        const char* o (nullptr);
+
+        switch (id)
         {
-          if      (mj >= 17)                         r = "-std=c++1z"; // 17
-          else if (mj >  15 || (mj == 15 && p >= 3)) r = "-std=c++1y"; // 14
-          else    /* ??? */                          r = "-std=c++0x"; // 11
+        case compiler_id::msvc:
+          {
+            // VC14u3 and later has /std:c++latest.
+            //
+            if (mj > 19 || (mj == 19 && (mi > 0 || (mi == 0 && p >= 24215))))
+              o = "/std:c++latest";
+
+            break;
+          }
+        case compiler_id::gcc:
+          {
+            if      (mj >= 5)            o = "-std=c++1z"; // 17
+            else if (mj == 4 && mi >= 8) o = "-std=c++1y"; // 14
+            else if (mj == 4 && mi >= 4) o = "-std=c++0x"; // 11
+
+            break;
+          }
+        case compiler_id::clang:
+          {
+            // Re-map Apple versions to vanilla Clang based on the following
+            // release point:
+            //
+            // 5.1 -> 3.4
+            // 6.0 -> 3.5
+            //
+            if (ci.id.variant == "apple")
+            {
+              if      (mj >= 6)            {mj = 3; mi = 5;}
+              else if (mj == 5 && mi >= 1) {mj = 3; mi = 4;}
+              else                         {mj = 3; mi = 0;}
+            }
+
+            if       (mj >  3 || (mj == 3 && mi >= 5)) o = "-std=c++1z"; // 17
+            else if  (mj == 3 && mi >= 4)              o = "-std=c++1y"; // 14
+            else     /* ??? */                         o = "-std=c++0x"; // 11
+
+            break;
+          }
+        case compiler_id::icc:
+          {
+            if      (mj >= 17)                         o = "-std=c++1z"; // 17
+            else if (mj >  15 || (mj == 15 && p >= 3)) o = "-std=c++1y"; // 14
+            else    /* ??? */                          o = "-std=c++0x"; // 11
+
+            break;
+          }
         }
-        else
-          assert (false);
+
+        if (o != nullptr)
+          r.push_back (o);
 
         return r;
       }
 
       // Otherwise translate the standard value.
       //
-      if (t == "msvc")
+      switch (id)
       {
-        // C++ standard-wise, with VC you got what you got up until 14u2.
-        // Starting with 14u3 there is now the /std: switch which defaults
-        // to c++14 but can be set to c++latest.
-        //
-        // The question is also whether we should verify that the requested
-        // standard is provided by this VC version. And if so, from which
-        // version should we say VC supports 11, 14, and 17? We should
-        // probably be as loose as possible here since the author will always
-        // be able to tighten (but not loosen) this in the buildfile (i.e.,
-        // detect unsupported versions).
-        //
-        // For now we are not going to bother doing this for C++03.
-        //
-        if (v != "98" && v != "03")
+      case compiler_id::msvc:
         {
-          bool sup (false);
-
-          if      (v == "11") // C++11 since VS2010/10.0.
-          {
-            sup = mj >= 16;
-          }
-          else if (v == "14") // C++14 since VS2015/14.0.
-          {
-            sup = mj >= 19;
-          }
-          else if (v == "17") // C++17 since VS2015/14.0u2.
+          // C++ standard-wise, with VC you got what you got up until 14u2.
+          // Starting with 14u3 there is now the /std: switch which defaults
+          // to c++14 but can be set to c++latest.
+          //
+          // The question is also whether we should verify that the requested
+          // standard is provided by this VC version. And if so, from which
+          // version should we say VC supports 11, 14, and 17? We should
+          // probably be as loose as possible here since the author will
+          // always be able to tighten (but not loosen) this in the buildfile
+          // (i.e., detect unsupported versions).
+          //
+          // For now we are not going to bother doing this for C++03.
+          //
+          if (v == nullptr)
+            ;
+          else if (*v != "98" && *v != "03")
           {
-            // Note: the VC15 compiler version is 19.10.
+            bool sup (false);
+
+            if      (*v == "11") // C++11 since VS2010/10.0.
+            {
+              sup = mj >= 16;
+            }
+            else if (*v == "14") // C++14 since VS2015/14.0.
+            {
+              sup = mj >= 19;
+            }
+            else if (*v == "17") // C++17 since VS2015/14.0u2.
+            {
+              // Note: the VC15 compiler version is 19.10.
+              //
+              sup = (mj > 19 ||
+                     (mj == 19 && (mi > 0 || (mi == 0 && p >= 23918))));
+            }
+
+            if (!sup)
+              fail << "C++" << *v << " is not supported by " << ci.signature <<
+                info << "required by " << project (rs) << '@' << rs.out_path ();
+
+            // VC14u3 and later has /std:
             //
-            sup = mj > 19 || (mj == 19 && (mi > 0 || (mi == 0 && p >= 23918)));
+            if (mj > 19 || (mj == 19 && (mi > 0 || (mi == 0 && p >= 24215))))
+            {
+              if (*v == "17")
+                r.push_back ("/std:c++latest");
+            }
           }
-
-          if (!sup)
-            fail << "C++" << v << " is not supported by " << ci.signature <<
-              info << "required by " << project (rs) << '@' << rs.out_path ();
-
-          // VC14u3 and later has /std:
+          break;
+        }
+      case compiler_id::gcc:
+      case compiler_id::clang:
+      case compiler_id::icc:
+        {
+          // Translate 11 to 0x, 14 to 1y, and 17 to 1z for compatibility with
+          // older versions of the compilers.
           //
-          if (mj > 19 || (mj == 19 && (mi > 0 || (mi == 0 && p >= 24215))))
+          if (v == nullptr)
+            ;
+          else
           {
-            if (v == "17")
-              r = "/std:c++latest";
+            string o ("-std=");
+
+            if      (*v == "98") o += "c++98";
+            else if (*v == "03") o += "c++03";
+            else if (*v == "11") o += "c++0x";
+            else if (*v == "14") o += "c++1y";
+            else if (*v == "17") o += "c++1z";
+            else o += *v; // In case the user specifies e.g., 'gnu++17'.
+
+            r.push_back (move (o));
           }
+          break;
         }
       }
-      else
-      {
-        // Translate 11 to 0x, 14 to 1y, and 17 to 1z for compatibility with
-        // older versions of the compilers.
-        //
-        r = "-std=";
-
-        if (v == "98")
-          r += "c++98";
-        else if (v == "03")
-          r += "c++03";
-        else if (v == "11")
-          r += "c++0x";
-        else if (v == "14")
-          r += "c++1y";
-        else if (v == "17")
-          r += "c++1z";
-        else
-          r += v; // In case the user specifies something like 'gnu++17'.
-      }
 
       return r;
     }