Cache process_path, use fallback search directory for binutils

21 files changed, 498 insertions, 144 deletions

diff --git a/build2/bin/guess b/build2/bin/guess
index 540e644..bcf9732 100644
--- a/build2/bin/guess
+++ b/build2/bin/guess
@@ -30,10 +30,12 @@ namespace build2
     //
     struct ar_info
     {
+      process_path ar_path;
       string ar_id;
       string ar_signature;
       string ar_checksum;
 
+      process_path ranlib_path;
       string ranlib_id;
       string ranlib_signature;
       string ranlib_checksum;
@@ -43,7 +45,7 @@ namespace build2
     // attemplated and the returned ranlib_* members will be left empty.
     //
     ar_info
-    guess_ar (const path& ar, const path* ranlib);
+    guess_ar (const path& ar, const path* ranlib, const dir_path& fallback);
 
     // ld information.
     //
@@ -67,13 +69,14 @@ namespace build2
     //
     struct ld_info
     {
+      process_path path;
       string id;
       string signature;
       string checksum;
     };
 
     ld_info
-    guess_ld (const path& ld);
+    guess_ld (const path& ld, const dir_path& fallback);
 
     // rc information.
     //
@@ -90,13 +93,14 @@ namespace build2
     //
     struct rc_info
     {
+      process_path path;
       string id;
       string signature;
       string checksum;
     };
 
     rc_info
-    guess_rc (const path& rc);
+    guess_rc (const path& rc, const dir_path& fallback);
   }
 }
 
diff --git a/build2/bin/guess.cxx b/build2/bin/guess.cxx
index de91db3..13f3933 100644
--- a/build2/bin/guess.cxx
+++ b/build2/bin/guess.cxx
@@ -18,17 +18,26 @@ namespace build2
       string signature;
       string checksum;
 
+      guess_result () = default;
+      guess_result (string&& i, string&& s)
+          : id (move (i)), signature (move (s)) {}
+
       bool
       empty () const {return id.empty ();}
     };
 
     ar_info
-    guess_ar (const path& ar, const path* rl)
+    guess_ar (const path& ar, const path* rl, const dir_path& fallback)
     {
       tracer trace ("bin::guess_ar");
 
       guess_result arr, rlr;
 
+      process_path arp (run_search (ar, true, fallback));
+      process_path rlp (rl != nullptr
+                        ? run_search (*rl, true, fallback)
+                        : process_path ());
+
       // Binutils, LLVM, and FreeBSD ar/ranlib all recognize the --version
       // option. While Microsoft's lib.exe doesn't support --version, it only
       // issues a warning and exits with zero status, printing its usual
@@ -43,23 +52,23 @@ namespace build2
           // "GNU ar ".
           //
           if (l.compare (0, 7, "GNU ar ") == 0)
-            return guess_result {"gnu", move (l), ""};
+            return guess_result ("gnu", move (l));
 
           // LLVM ar --version output has a line that starts with
           // "LLVM version ".
           //
           if (l.compare (0, 13, "LLVM version ") == 0)
-            return guess_result {"llvm", move (l), ""};
+            return guess_result ("llvm", move (l));
 
           // FreeBSD ar --verison output starts with "BSD ar ".
           //
           if (l.compare (0, 7, "BSD ar ") == 0)
-            return guess_result {"bsd", move (l), ""};
+            return guess_result ("bsd", move (l));
 
           // Microsoft lib.exe output starts with "Microsoft (R) ".
           //
           if (l.compare (0, 14, "Microsoft (R) ") == 0)
-            return guess_result {"msvc", move (l), ""};
+            return guess_result ("msvc", move (l));
 
           return guess_result ();
         };
@@ -69,7 +78,7 @@ namespace build2
         // (yes, it goes to stdout) but that seems harmless.
         //
         sha256 cs;
-        arr = run<guess_result> (ar, "--version", f, false, false, &cs);
+        arr = run<guess_result> (arp, "--version", f, false, false, &cs);
 
         if (!arr.empty ())
           arr.checksum = cs.string ();
@@ -85,14 +94,14 @@ namespace build2
         auto f = [] (string& l) -> guess_result
         {
           return l.find (" ar ") != string::npos
-            ? guess_result {"generic", move (l), ""}
+            ? guess_result ("generic", move (l))
             : guess_result ();
         };
 
         // Redirect STDERR to STDOUT and ignore exit status.
         //
         sha256 cs;
-        arr = run<guess_result> (ar, f, false, true, &cs);
+        arr = run<guess_result> (arp, f, false, true, &cs);
 
         if (!arr.empty ())
         {
@@ -116,24 +125,24 @@ namespace build2
             // "GNU ranlib ".
             //
             if (l.compare (0, 11, "GNU ranlib ") == 0)
-              return guess_result {"gnu", move (l), ""};
+              return guess_result ("gnu", move (l));
 
             // "LLVM version ".
             //
             if (l.compare (0, 13, "LLVM version ") == 0)
-              return guess_result {"llvm", move (l), ""};
+              return guess_result ("llvm", move (l));
 
             // On FreeBSD we get "ranlib" rather than "BSD ranlib" for some
             // reason. Which means we can't really call it 'bsd' for sure.
             //
             //if (l.compare (0, 7, "ranlib ") == 0)
-            //  return guess_result {"bsd", move (l), ""};
+            //  return guess_result ("bsd", move (l));
 
             return guess_result ();
           };
 
           sha256 cs;
-          rlr = run<guess_result> (*rl, "--version", f, false, false, &cs);
+          rlr = run<guess_result> (rlp, "--version", f, false, false, &cs);
 
           if (!rlr.empty ())
             rlr.checksum = cs.string ();
@@ -146,14 +155,14 @@ namespace build2
           auto f = [] (string& l) -> guess_result
           {
             return l.find ("ranlib") != string::npos
-              ? guess_result {"generic", move (l), ""}
+              ? guess_result ("generic", move (l))
               : guess_result ();
           };
 
           // Redirect STDERR to STDOUT and ignore exit status.
           //
           sha256 cs;
-          rlr = run<guess_result> (*rl, f, false, true, &cs);
+          rlr = run<guess_result> (rlp, f, false, true, &cs);
 
           if (!rlr.empty ())
           {
@@ -167,17 +176,19 @@ namespace build2
       }
 
       return ar_info {
-        move (arr.id), move (arr.signature), move (arr.checksum),
-        move (rlr.id), move (rlr.signature), move (rlr.checksum)};
+        move (arp), move (arr.id), move (arr.signature), move (arr.checksum),
+        move (rlp), move (rlr.id), move (rlr.signature), move (rlr.checksum)};
     }
 
     ld_info
-    guess_ld (const path& ld)
+    guess_ld (const path& ld, const dir_path& fallback)
     {
       tracer trace ("bin::guess_ld");
 
       guess_result r;
 
+      process_path pp (run_search (ld, true, fallback));
+
       // Binutils ld recognizes the --version option. Microsoft's link.exe
       // doesn't support --version (nor any other way to get the version
       // without the error exist status) but it will still print its banner.
@@ -194,16 +205,16 @@ namespace build2
           // Microsoft link.exe output starts with "Microsoft (R) ".
           //
           if (l.compare (0, 14, "Microsoft (R) ") == 0)
-            return guess_result {"msvc", move (l), ""};
+            return guess_result ("msvc", move (l));
 
           // Binutils ld.bfd --version output has a line that starts with
           // "GNU ld " while ld.gold -- "GNU gold".
           //
           if (l.compare (0, 7, "GNU ld ") == 0)
-            return guess_result {"gnu", move (l), ""};
+            return guess_result ("gnu", move (l));
 
           if (l.compare (0, 9, "GNU gold ") == 0)
-            return guess_result {"gold", move (l), ""};
+            return guess_result ("gold", move (l));
 
           return guess_result ();
         };
@@ -213,7 +224,7 @@ namespace build2
         // but that seems harmless.
         //
         sha256 cs;
-        r = run<guess_result> (ld, "--version", f, false, true, &cs);
+        r = run<guess_result> (pp, "--version", f, false, true, &cs);
 
         if (!r.empty ())
           r.checksum = cs.string ();
@@ -231,20 +242,20 @@ namespace build2
           // @(#)PROGRAM:ld  PROJECT:ld64-242.2
           //
           if (l.find ("PROJECT:ld64") != string::npos)
-            return guess_result {"ld64", move (l), ""};
+            return guess_result ("ld64", move (l));
 
           // Old ld has "cctools" in the first line, for example:
           //
           // Apple Computer, Inc. version cctools-622.9~2
           //
           if (l.find ("cctools") != string::npos)
-            return guess_result {"cctools", move (l), ""};
+            return guess_result ("cctools", move (l));
 
           return guess_result ();
         };
 
         sha256 cs;
-        r = run<guess_result> (ld, "-v", f, false, false, &cs);
+        r = run<guess_result> (pp, "-v", f, false, false, &cs);
 
         if (!r.empty ())
           r.checksum = cs.string ();
@@ -262,7 +273,7 @@ namespace build2
           // LLVM Linker Version: 3.7
           //
           if (l.compare (0, 19, "LLVM Linker Version") == 0)
-            return guess_result {"llvm", move (l), ""};
+            return guess_result ("llvm", move (l));
 
           return guess_result ();
         };
@@ -271,7 +282,7 @@ namespace build2
         // option.
         //
         sha256 cs;
-        r = run<guess_result> (ld, "-version", f, false, false, &cs);
+        r = run<guess_result> (pp, "-version", f, false, false, &cs);
 
         if (!r.empty ())
           r.checksum = cs.string ();
@@ -280,16 +291,19 @@ namespace build2
       if (r.empty ())
         fail << "unable to guess " << ld << " signature";
 
-      return ld_info {move (r.id), move (r.signature), move (r.checksum)};
+      return ld_info {
+        move (pp), move (r.id), move (r.signature), move (r.checksum)};
     }
 
     rc_info
-    guess_rc (const path& rc)
+    guess_rc (const path& rc, const dir_path& fallback)
     {
       tracer trace ("bin::guess_rc");
 
       guess_result r;
 
+      process_path pp (run_search (rc, true, fallback));
+
       // Binutils windres recognizes the --version option.
       //
       {
@@ -299,7 +313,7 @@ namespace build2
           // "GNU windres ".
           //
           if (l.compare (0, 12, "GNU windres ") == 0)
-            return guess_result {"gnu", move (l), ""};
+            return guess_result ("gnu", move (l));
 
           return guess_result ();
         };
@@ -308,7 +322,7 @@ namespace build2
         // option.
         //
         sha256 cs;
-        r = run<guess_result> (rc, "--version", f, false, false, &cs);
+        r = run<guess_result> (pp, "--version", f, false, false, &cs);
 
         if (!r.empty ())
           r.checksum = cs.string ();
@@ -322,13 +336,13 @@ namespace build2
         auto f = [] (string& l) -> guess_result
         {
           if (l.compare (0, 14, "Microsoft (R) ") == 0)
-            return guess_result {"msvc", move (l), ""};
+            return guess_result ("msvc", move (l));
 
           return guess_result ();
         };
 
         sha256 cs;
-        r = run<guess_result> (rc, "/?", f, false, false, &cs);
+        r = run<guess_result> (pp, "/?", f, false, false, &cs);
 
         if (!r.empty ())
           r.checksum = cs.string ();
@@ -337,7 +351,8 @@ namespace build2
       if (r.empty ())
         fail << "unable to guess " << rc << " signature";
 
-      return rc_info {move (r.id), move (r.signature), move (r.checksum)};
+      return rc_info {
+        move (pp), move (r.id), move (r.signature), move (r.checksum)};
     }
   }
 }
diff --git a/build2/bin/init.cxx b/build2/bin/init.cxx
index 424a729..125bc7d 100644
--- a/build2/bin/init.cxx
+++ b/build2/bin/init.cxx
@@ -273,8 +273,12 @@ namespace build2
           {
             const string& s (cast<string> (*v));
 
-            if (s.find ('*') == string::npos)
+            if (s.empty () ||
+                (!path::traits::is_separator (s.back ()) &&
+                 s.find ('*') == string::npos))
+            {
               fail << "missing '*' in binutils pattern '" << s << "'";
+            }
 
             r.assign<string> ("bin.pattern") = s;
             new_val = new_val || p.second; // False for a hinted value.
@@ -428,8 +432,11 @@ namespace build2
       {
         auto& v (var_pool);
 
-        v.insert<path> ("config.bin.ar", true);
-        v.insert<path> ("config.bin.ranlib", true);
+        v.insert<process_path> ("bin.rc.path");
+        v.insert<process_path> ("bin.ranlib.path");
+
+        v.insert<path>         ("config.bin.ar", true);
+        v.insert<path>         ("config.bin.ranlib", true);
       }
 
       // Configure.
@@ -456,6 +463,11 @@ namespace build2
         const string& tsys (cast<string> (r["bin.target.system"]));
         const char* ar_d (tsys == "win32-msvc" ? "lib" : "ar");
 
+        // This can be either a pattern or a fallback search directory.
+        //
+        const string* pat (cast_null<string> (r["bin.pattern"]));
+        bool fb (pat != nullptr && path::traits::is_separator (pat->back ()));
+
         // Don't save the default value to config.build so that if the user
         // changes, say, the C++ compiler (which hinted the pattern), then
         // ar will automatically change as well.
@@ -464,7 +476,7 @@ namespace build2
           config::required (
             r,
             "config.bin.ar",
-            path (apply_pattern (ar_d, cast_null<string> (r["bin.pattern"]))),
+            path (apply_pattern (ar_d, fb ? nullptr : pat)),
             false,
             config::save_commented));
 
@@ -482,7 +494,8 @@ namespace build2
         if (ranlib != nullptr && ranlib->empty ()) // @@ BC LT [null].
           ranlib = nullptr;
 
-        ar_info ari (guess_ar (ar, ranlib));
+        ar_info ari (
+          guess_ar (ar, ranlib, fb ? dir_path (*pat) : dir_path ()));
 
         // If this is a new value (e.g., we are configuring), then print the
         // report at verbosity level 2 and up (-v).
@@ -492,7 +505,7 @@ namespace build2
           diag_record dr (text);
 
           dr << "bin.ar " << project (r) << '@' << r.out_path () << '\n'
-             << "  ar         " << ar << '\n'
+             << "  ar         " << ari.ar_path << '\n'
              << "  id         " << ari.ar_id << '\n'
              << "  signature  " << ari.ar_signature << '\n'
              << "  checksum   " << ari.ar_checksum;
@@ -500,23 +513,25 @@ namespace build2
           if (ranlib != nullptr)
           {
             dr << '\n'
-               << "  ranlib     " << *ranlib << '\n'
+               << "  ranlib     " << ari.ranlib_path << '\n'
                << "  id         " << ari.ranlib_id << '\n'
                << "  signature  " << ari.ranlib_signature << '\n'
                << "  checksum   " << ari.ranlib_checksum;
           }
         }
 
-        r.assign<string> ("bin.ar.id") = move (ari.ar_id);
-        r.assign<string> ("bin.ar.signature") = move (ari.ar_signature);
-        r.assign<string> ("bin.ar.checksum") = move (ari.ar_checksum);
+        r.assign<process_path> ("bin.ar.path")      = move (ari.ar_path);
+        r.assign<string>       ("bin.ar.id")        = move (ari.ar_id);
+        r.assign<string>       ("bin.ar.signature") = move (ari.ar_signature);
+        r.assign<string>       ("bin.ar.checksum")  = move (ari.ar_checksum);
 
         if (ranlib != nullptr)
         {
-          r.assign<string> ("bin.ranlib.id") = move (ari.ranlib_id);
-          r.assign<string> ("bin.ranlib.signature") =
+          r.assign<process_path> ("bin.ranlib.path") = move (ari.ranlib_path);
+          r.assign<string>       ("bin.ranlib.id") = move (ari.ranlib_id);
+          r.assign<string>       ("bin.ranlib.signature") =
             move (ari.ranlib_signature);
-          r.assign<string> ("bin.ranlib.checksum") =
+          r.assign<string>       ("bin.ranlib.checksum") =
             move (ari.ranlib_checksum);
         }
       }
@@ -570,7 +585,8 @@ namespace build2
       {
         auto& v (var_pool);
 
-        v.insert<path> ("config.bin.ld", true);
+        v.insert<process_path> ("bin.ld.path");
+        v.insert<path>         ("config.bin.ld", true);
       }
 
       // Configure.
@@ -584,16 +600,21 @@ namespace build2
         const string& tsys (cast<string> (r["bin.target.system"]));
         const char* ld_d (tsys == "win32-msvc" ? "link" : "ld");
 
+        // This can be either a pattern or a fallback search directory.
+        //
+        const string* pat (cast_null<string> (r["bin.pattern"]));
+        bool fb (pat != nullptr && path::traits::is_separator (pat->back ()));
+
         auto p (
           config::required (
             r,
             "config.bin.ld",
-            path (apply_pattern (ld_d, cast_null<string> (r["bin.pattern"]))),
+            path (apply_pattern (ld_d, fb ? nullptr : pat)),
             false,
             config::save_commented));
 
         const path& ld (cast<path> (p.first));
-        ld_info ldi (guess_ld (ld));
+        ld_info ldi (guess_ld (ld, fb ? dir_path (*pat) : dir_path ()));
 
         // If this is a new value (e.g., we are configuring), then print the
         // report at verbosity level 2 and up (-v).
@@ -601,15 +622,16 @@ namespace build2
         if (verb >= (p.second ? 2 : 3))
         {
           text << "bin.ld " << project (r) << '@' << r.out_path () << '\n'
-               << "  ld         " << ld << '\n'
+               << "  ld         " << ldi.path << '\n'
                << "  id         " << ldi.id << '\n'
                << "  signature  " << ldi.signature << '\n'
                << "  checksum   " << ldi.checksum;
         }
 
-        r.assign<string> ("bin.ld.id") = move (ldi.id);
-        r.assign<string> ("bin.ld.signature") = move (ldi.signature);
-        r.assign<string> ("bin.ld.checksum") = move (ldi.checksum);
+        r.assign<process_path> ("bin.ld.path")      = move (ldi.path);
+        r.assign<string>       ("bin.ld.id")        = move (ldi.id);
+        r.assign<string>       ("bin.ld.signature") = move (ldi.signature);
+        r.assign<string>       ("bin.ld.checksum")  = move (ldi.checksum);
       }
 
       return true;
@@ -674,7 +696,8 @@ namespace build2
       {
         auto& v (var_pool);
 
-        v.insert<path> ("config.bin.rc", true);
+        v.insert<process_path> ("bin.rc.path");
+        v.insert<path>         ("config.bin.rc", true);
       }
 
       // Configure.
@@ -688,16 +711,21 @@ namespace build2
         const string& tsys (cast<string> (r["bin.target.system"]));
         const char* rc_d (tsys == "win32-msvc" ? "rc" : "windres");
 
+        // This can be either a pattern or a fallback search directory.
+        //
+        const string* pat (cast_null<string> (r["bin.pattern"]));
+        bool fb (pat != nullptr && path::traits::is_separator (pat->back ()));
+
         auto p (
           config::required (
             r,
             "config.bin.rc",
-            path (apply_pattern (rc_d, cast_null<string> (r["bin.pattern"]))),
+            path (apply_pattern (rc_d, fb ? nullptr : pat)),
             false,
             config::save_commented));
 
         const path& rc (cast<path> (p.first));
-        rc_info rci (guess_rc (rc));
+        rc_info rci (guess_rc (rc, fb ? dir_path (*pat) : dir_path ()));
 
         // If this is a new value (e.g., we are configuring), then print the
         // report at verbosity level 2 and up (-v).
@@ -705,15 +733,16 @@ namespace build2
         if (verb >= (p.second ? 2 : 3))
         {
           text << "bin.rc " << project (r) << '@' << r.out_path () << '\n'
-               << "  rc         " << rc << '\n'
+               << "  rc         " << rci.path << '\n'
                << "  id         " << rci.id << '\n'
                << "  signature  " << rci.signature << '\n'
                << "  checksum   " << rci.checksum;
         }
 
-        r.assign<string> ("bin.rc.id") = move (rci.id);
-        r.assign<string> ("bin.rc.signature") = move (rci.signature);
-        r.assign<string> ("bin.rc.checksum") = move (rci.checksum);
+        r.assign<process_path> ("bin.rc.path")      = move (rci.path);
+        r.assign<string>       ("bin.rc.id")        = move (rci.id);
+        r.assign<string>       ("bin.rc.signature") = move (rci.signature);
+        r.assign<string>       ("bin.rc.checksum")  = move (rci.checksum);
       }
 
       return true;
diff --git a/build2/c/init.cxx b/build2/c/init.cxx
index 52bf0b6..88f0b2b 100644
--- a/build2/c/init.cxx
+++ b/build2/c/init.cxx
@@ -121,16 +121,17 @@ namespace build2
 
           // Note: some overridable, some not.
           //
-          v.insert<path>     ("config.c",          true),
-          v.insert<strings>  ("config.c.poptions", true),
-          v.insert<strings>  ("config.c.coptions", true),
-          v.insert<strings>  ("config.c.loptions", true),
-          v.insert<strings>  ("config.c.libs",     true),
-
-          v.insert<strings>  ("c.poptions"),
-          v.insert<strings>  ("c.coptions"),
-          v.insert<strings>  ("c.loptions"),
-          v.insert<strings>  ("c.libs"),
+          v.insert<path>    ("config.c",          true),
+          v.insert<strings> ("config.c.poptions", true),
+          v.insert<strings> ("config.c.coptions", true),
+          v.insert<strings> ("config.c.loptions", true),
+          v.insert<strings> ("config.c.libs",     true),
+
+          v.insert<process_path> ("c.path"),
+          v.insert<strings>      ("c.poptions"),
+          v.insert<strings>      ("c.coptions"),
+          v.insert<strings>      ("c.loptions"),
+          v.insert<strings>      ("c.libs"),
 
           v["cc.poptions"],
           v["cc.coptions"],
diff --git a/build2/cc/common b/build2/cc/common
index 2be290a..987fe7b 100644
--- a/build2/cc/common
+++ b/build2/cc/common
@@ -36,6 +36,7 @@ namespace build2
       const variable& config_x_loptions;
       const variable& config_x_libs;
 
+      const variable& x_path;
       const variable& x_poptions;
       const variable& x_coptions;
       const variable& x_loptions;
diff --git a/build2/cc/compile.cxx b/build2/cc/compile.cxx
index 92ddf3b..33be687 100644
--- a/build2/cc/compile.cxx
+++ b/build2/cc/compile.cxx
@@ -644,12 +644,14 @@ namespace build2
 
       // Initialize lazily, only if required.
       //
+      const process_path* xc (nullptr);
       cstrings args;
       string std; // Storage.
 
-      auto init_args = [&t, lo, &src, &rs, &args, &std, this] ()
+      auto init_args = [&t, lo, &src, &rs, &xc, &args, &std, this] ()
       {
-        args.push_back (cast<path> (rs[config_x]).string ().c_str ());
+        xc = &cast<process_path> (rs[x_path]);
+        args.push_back (xc->recall_string ());
 
         // Add *.export.poptions from prerequisite libraries. Note that here
         // we don't need to see group members (see apply()).
@@ -1034,7 +1036,8 @@ namespace build2
             // For VC with /EP we need a pipe to stderr and stdout should go
             // to /dev/null.
             //
-            process pr (args.data (),
+            process pr (*xc,
+                        args.data (),
                         0,
                         cid == "msvc" ? -2 : -1,
                         cid == "msvc" ? -1 : 2);
@@ -1261,7 +1264,8 @@ namespace build2
       scope& rs (*bs.root_scope ());
       otype ct (compile_type (t));
 
-      cstrings args {cast<path> (rs[config_x]).string ().c_str ()};
+      const process_path& xc (cast<process_path> (rs[x_path]));
+      cstrings args {xc.recall_string ()};
 
       // Translate paths to relative (to working directory) ones. This
       // results in easier to read diagnostics.
@@ -1418,7 +1422,7 @@ namespace build2
         //
         bool filter (cid == "msvc");
 
-        process pr (args.data (), 0, (filter ? -1 : 2));
+        process pr (xc, args.data (), 0, (filter ? -1 : 2));
 
         if (filter)
         {
diff --git a/build2/cc/guess b/build2/cc/guess
index d852a5c..c49fb4f 100644
--- a/build2/cc/guess
+++ b/build2/cc/guess
@@ -100,10 +100,14 @@ namespace build2
     // derived for some toolchains. For example, i686-w64-mingw32-*-4.9.
     //
     // The bin_pattern is the binutils program pattern that could sometimes be
-    // derived for some toolchains. For example, i686-w64-mingw32-*.
+    // derived for some toolchains. For example, i686-w64-mingw32-*. If the
+    // pattern could not be derived, then it could contain a fallback search
+    // directory, in which case it will end with a directory separator but
+    // will not contain '*'.
     //
     struct compiler_info
     {
+      process_path path;
       compiler_id id;
       compiler_version version;
       string signature;
diff --git a/build2/cc/guess.cxx b/build2/cc/guess.cxx
index 5001879..c2b552a 100644
--- a/build2/cc/guess.cxx
+++ b/build2/cc/guess.cxx
@@ -105,6 +105,11 @@ namespace build2
       compiler_id id;
       string signature;
       string checksum;
+      process_path path;
+
+      guess_result () = default;
+      guess_result (compiler_id&& i, string&& s)
+          : id (move (i)), signature (move (s)) {}
 
       bool
       empty () const {return id.empty ();}
@@ -117,6 +122,8 @@ namespace build2
 
       guess_result r;
 
+      process_path pp (run_search (xc, true));
+
       // Start with -v. This will cover gcc and clang.
       //
       // While icc also writes what may seem like something we can use to
@@ -152,7 +159,7 @@ namespace build2
           // gcc version 6.0.0 20160131 (experimental) (GCC)
           //
           if (l.compare (0, 4, "gcc ") == 0)
-            return guess_result {{"gcc", ""}, move (l), ""};
+            return guess_result (compiler_id {"gcc", ""}, move (l));
 
           // The Apple clang/clang++ -v output will have a line (currently
           // first) in the form:
@@ -182,7 +189,7 @@ namespace build2
           if (l.compare (0, 6, "Apple ") == 0 &&
               (l.compare (6, 5, "LLVM ") == 0 ||
                l.compare (6, 6, "clang ") == 0))
-            return guess_result {{"clang", "apple"}, move (l), ""};
+            return guess_result (compiler_id {"clang", "apple"}, move (l));
 
           // The vanilla clang/clang++ -v output will have a line (currently
           // first) in the form:
@@ -197,7 +204,7 @@ namespace build2
           // clang version 3.7.0 (tags/RELEASE_370/final)
           //
           if (l.find ("clang ") != string::npos)
-            return guess_result {{"clang", ""}, move (l), ""};
+            return guess_result (compiler_id {"clang", ""}, move (l));
 
           return guess_result ();
         };
@@ -216,7 +223,7 @@ namespace build2
         // Suppress all the compiler errors because we may be trying an
         // unsupported option.
         //
-        r = run<guess_result> (xc, "-v", f, false, false, &cs);
+        r = run<guess_result> (pp, "-v", f, false, false, &cs);
 
         if (!r.empty ())
           r.checksum = cs.string ();
@@ -239,12 +246,12 @@ namespace build2
           // icc (ICC) 16.0.2 20160204
           //
           if (l.find (" (ICC) ") != string::npos)
-            return guess_result {{"icc", ""}, move (l), ""};
+            return guess_result (compiler_id {"icc", ""}, move (l));
 
           return guess_result ();
         };
 
-        r = run<guess_result> (xc, "--version", f, false);
+        r = run<guess_result> (pp, "--version", f, false);
       }
 
       // Finally try to run it without any options to detect msvc.
@@ -271,12 +278,12 @@ namespace build2
           //
           if (l.find ("Microsoft (R)") != string::npos &&
               l.find ("C/C++") != string::npos)
-            return guess_result {{"msvc", ""}, move (l), ""};
+            return guess_result (compiler_id {"msvc", ""}, move (l));
 
           return guess_result ();
         };
 
-        r = run<guess_result> (xc, f, false);
+        r = run<guess_result> (pp, f, false);
       }
 
       if (!r.empty ())
@@ -290,8 +297,12 @@ namespace build2
           r = guess_result ();
         }
         else
+        {
           l5 ([&]{trace << xc << " is " << r.id << ": '"
                         << r.signature << "'";});
+
+          r.path = move (pp);
+        }
       }
       else
         l4 ([&]{trace << "unable to determine compiler type of " << xc;});
@@ -463,6 +474,7 @@ namespace build2
         pat = pattern (xc, xl == lang::c ? "cc" : "c++");
 
       return compiler_info {
+        move (gr.path),
         move (gr.id),
         move (v),
         move (gr.signature),
@@ -579,6 +591,7 @@ namespace build2
         pat = pattern (xc, xl == lang::c ? "cc" : "c++");
 
       return compiler_info {
+        move (gr.path),
         move (gr.id),
         move (v),
         move (gr.signature),
@@ -798,6 +811,7 @@ namespace build2
       sha256 cs (s);
 
       return compiler_info {
+        move (gr.path),
         move (gr.id),
         move (v),
         move (gr.signature),
@@ -1011,6 +1025,7 @@ namespace build2
       sha256 cs (s);
 
       return compiler_info {
+        move (gr.path),
         move (gr.id),
         move (v),
         move (gr.signature),
@@ -1075,11 +1090,12 @@ namespace build2
       // Derive binutils pattern unless this has already been done by the
       // compiler-specific code.
       //
+
+      // When cross-compiling the whole toolchain is normally prefixed with
+      // the target triplet, e.g., x86_64-w64-mingw32-{gcc,g++,ar,ld}.
+      //
       if (r.bin_pattern.empty ())
       {
-        // When cross-compiling the whole toolchain is normally prefixed with
-        // the target triplet, e.g., x86_64-w64-mingw32-{gcc,g++,ar,ld}.
-        //
         // BTW, for GCC we also get gcc-{ar,ranlib} which add support for the
         // LTO plugin though it seems more recent GNU binutils (2.25) are able
         // to load the plugin when needed automatically. So it doesn't seem we
@@ -1103,6 +1119,17 @@ namespace build2
         }
       }
 
+      // If we could not derive the pattern, then see if we can come up with a
+      // fallback search directory.
+      //
+      if (r.bin_pattern.empty ())
+      {
+        const path& p (r.path.recall.empty () ? xc : r.path.recall);
+
+        if (!p.simple ())
+          r.bin_pattern = p.directory ().representation (); // Trailing slash.
+      }
+
       return r;
     }
 
diff --git a/build2/cc/link b/build2/cc/link
index 8be386f..f6a16c0 100644
--- a/build2/cc/link
+++ b/build2/cc/link
@@ -56,10 +56,14 @@ namespace build2
       // Alternative search logic for VC (msvc.cxx).
       //
       bin::liba*
-      msvc_search_static (const path&, const dir_path&, prerequisite&) const;
+      msvc_search_static (const process_path&,
+                          const dir_path&,
+                          prerequisite&) const;
 
       bin::libs*
-      msvc_search_shared (const path&, const dir_path&, prerequisite&) const;
+      msvc_search_shared (const process_path&,
+                          const dir_path&,
+                          prerequisite&) const;
 
       target*
       search_library (optional<dir_paths>&, prerequisite&) const;
diff --git a/build2/cc/link.cxx b/build2/cc/link.cxx
index 61dd0ad..7a6b059 100644
--- a/build2/cc/link.cxx
+++ b/build2/cc/link.cxx
@@ -420,7 +420,7 @@ namespace build2
         if (cid == "msvc")
         {
           scope& rs (*p.scope.root_scope ());
-          const path& ld (cast<path> (rs["config.bin.ld"]));
+          const process_path& ld (cast<process_path> (rs["bin.ld.path"]));
 
           if (s == nullptr && !sn.empty ())
             s = msvc_search_shared (ld, d, p);
@@ -1135,10 +1135,12 @@ namespace build2
           {
             path of (relative (manifest));
 
+            const process_path& rc (cast<process_path> (rs["bin.rc.path"]));
+
             // @@ Would be good to add this to depdb (e.g,, rc changes).
             //
             const char* args[] = {
-              cast<path> (rs["config.bin.rc"]).string ().c_str (),
+              rc.recall_string (),
               "--input-format=rc",
               "--output-format=coff",
               "-o", of.string ().c_str (),
@@ -1149,7 +1151,7 @@ namespace build2
 
             try
             {
-              process pr (args, -1);
+              process pr (rc, args, -1);
 
               try
               {
@@ -1224,7 +1226,7 @@ namespace build2
       //
       if (lt == otype::a)
       {
-        ranlib = rs["config.bin.ranlib"];
+        ranlib = rs["bin.ranlib.path"];
 
         if (ranlib && ranlib->empty ()) // @@ BC LT [null].
           ranlib = lookup ();
@@ -1481,11 +1483,12 @@ namespace build2
       //
       path relt (relative (t.path ()));
 
+      const process_path* ld (nullptr);
       switch (lt)
       {
       case otype::a:
         {
-          args[0] = cast<path> (rs["config.bin.ar"]).string ().c_str ();
+          ld = &cast<process_path> (rs["bin.ar.path"]);
 
           if (cid == "msvc")
           {
@@ -1516,7 +1519,7 @@ namespace build2
           {
             // Using link.exe directly.
             //
-            args[0] = cast<path> (rs["config.bin.ld"]).string ().c_str ();
+            ld = &cast<process_path> (rs["bin.ld.path"]);
             args.push_back ("/NOLOGO");
 
             if (lt == otype::s)
@@ -1608,7 +1611,7 @@ namespace build2
           }
           else
           {
-            args[0] = cast<path> (rs[config_x]).string ().c_str ();
+            ld = &cast<process_path> (rs[x_path]);
 
             // Add the option that triggers building a shared library and take
             // care of any extras (e.g., import library).
@@ -1639,6 +1642,8 @@ namespace build2
         }
       }
 
+      args[0] = ld->recall_string ();
+
       for (target* pt: t.prerequisite_targets)
       {
         file* f;
@@ -1709,7 +1714,7 @@ namespace build2
         //
         bool filter (cid == "msvc" && lt != otype::a);
 
-        process pr (args.data (), 0, (filter ? -1 : 2));
+        process pr (*ld, args.data (), 0, (filter ? -1 : 2));
 
         if (filter)
         {
@@ -1756,8 +1761,10 @@ namespace build2
 
       if (ranlib)
       {
+        const process_path& rl (cast<process_path> (ranlib));
+
         const char* args[] = {
-          cast<path> (ranlib).string ().c_str (),
+          rl.recall_string (),
           relt.string ().c_str (),
           nullptr};
 
@@ -1766,7 +1773,7 @@ namespace build2
 
         try
         {
-          process pr (args);
+          process pr (rl, args);
 
           if (!pr.wait ())
             throw failed ();
diff --git a/build2/cc/module.cxx b/build2/cc/module.cxx
index d3849e1..4926fac 100644
--- a/build2/cc/module.cxx
+++ b/build2/cc/module.cxx
@@ -105,7 +105,7 @@ namespace build2
 
           {
             dr << x << ' ' << project (r) << '@' << r.out_path () << '\n'
-               << "  " << left << setw (11) << x << xc << '\n'
+               << "  " << left << setw (11) << x << ci.path << '\n'
                << "  id         " << ci.id << '\n'
                << "  version    " << ci.version.string << '\n'
                << "  major      " << ci.version.major << '\n'
@@ -129,6 +129,7 @@ namespace build2
           }
         }
 
+        r.assign (x_path) = move (ci.path);
         r.assign (x_id) = ci.id.string ();
         r.assign (x_id_type) = move (ci.id.type);
         r.assign (x_id_variant) = move (ci.id.variant);
diff --git a/build2/cc/msvc.cxx b/build2/cc/msvc.cxx
index 84020d0..84f5853 100644
--- a/build2/cc/msvc.cxx
+++ b/build2/cc/msvc.cxx
@@ -105,7 +105,7 @@ namespace build2
     // Return otype::e if it is neither (which we quietly ignore).
     //
     static otype
-    library_type (const path& ld, const path& l)
+    library_type (const process_path& ld, const path& l)
     {
       // The are several reasonably reliable methods to tell whether it is a
       // static or import library. One is lib.exe /LIST -- if there aren't any
@@ -125,7 +125,7 @@ namespace build2
       // for libraries then we have bin.ld. So we will use the link.exe /DUMP
       // /ARCHIVEMEMBERS.
       //
-      const char* args[] = {ld.string ().c_str (),
+      const char* args[] = {ld.recall_string (),
                             "/DUMP",               // Must come first.
                             "/NOLOGO",
                             "/ARCHIVEMEMBERS",
@@ -135,7 +135,7 @@ namespace build2
       // Link.exe seem to always dump everything to stdout but just in case
       // redirect stderr to stdout.
       //
-      process pr (start_run (args, false));
+      process pr (run_start (ld, args, false));
 
       bool obj (false), dll (false);
       string s;
@@ -192,11 +192,11 @@ namespace build2
       }
       catch (const ifdstream::failure&)
       {
-        // Presumably the child process failed. Let finish_run() deal with
+        // Presumably the child process failed. Let run_finish() deal with
         // that.
       }
 
-      if (!finish_run (args, false, pr, s))
+      if (!run_finish (args, false, pr, s))
         return otype::e;
 
       if (obj && dll)
@@ -217,7 +217,7 @@ namespace build2
     template <typename T>
     static T*
     msvc_search_library (const char* mod,
-                         const path& ld,
+                         const process_path& ld,
                          const dir_path& d,
                          prerequisite& p,
                          otype lt,
@@ -275,7 +275,7 @@ namespace build2
     }
 
     liba* link::
-    msvc_search_static (const path& ld,
+    msvc_search_static (const process_path& ld,
                         const dir_path& d,
                         prerequisite& p) const
     {
@@ -302,7 +302,7 @@ namespace build2
     }
 
     libs* link::
-    msvc_search_shared (const path& ld,
+    msvc_search_shared (const process_path& ld,
                         const dir_path& d,
                         prerequisite& p) const
     {
diff --git a/build2/cli/init.cxx b/build2/cli/init.cxx
index 467cf82..49947f5 100644
--- a/build2/cli/init.cxx
+++ b/build2/cli/init.cxx
@@ -58,7 +58,8 @@ namespace build2
         v.insert<path>    ("config.cli",         true);
         v.insert<strings> ("config.cli.options", true);
 
-        v.insert<strings> ("cli.options");
+        v.insert<process_path> ("cli.path");
+        v.insert<strings>      ("cli.options");
       }
 
       // Register target types.
@@ -91,20 +92,28 @@ namespace build2
       {
         // config.cli
         //
+        process_path pp;
 
-        // Return version or empty string if unable to execute (e.g., the cli
-        // executable is not found).
+        // Return version or empty string if the cli executable is not found.
         //
-        auto test = [optional] (const path& cli) -> string
+        // @@ This needs some more thinking/cleanup. Specifically, what does
+        //    it mean "cli not found"? Is it just not found in PATH? That plus
+        //    was not able to execute (e.g., some shared libraries missing)?
+        //    That plus cli that we found is something else?
+        //
+        auto test = [optional, &pp] (const path& cli) -> string
         {
-          const char* args[] = {cli.string ().c_str (), "--version", nullptr};
-
-          if (verb >= 3)
-            print_process (args);
+          const char* args[] = {nullptr, "--version", nullptr};
 
           try
           {
-            process pr (args, 0, -1); // Open pipe to stdout.
+            pp = process::path_search (cli, true); // Can throw.
+            args[0] = pp.recall_string ();
+
+            if (verb >= 3)
+              print_process (args);
+
+            process pr (pp, args, 0, -1); // Open pipe to stdout.
 
             try
             {
@@ -146,7 +155,7 @@ namespace build2
             // found). So it would be good to redirect child's STDERR.
             //
             if (!optional)
-              error << "unable to execute " << cli << ": " << e.what ();
+              error << "unable to execute " << args[0] << ": " << e.what ();
 
             if (e.child ())
               exit (1);
@@ -216,9 +225,12 @@ namespace build2
           if (unconf)
             dr << "  cli        " << "not found, leaving unconfigured";
           else
-            dr << "  cli        " << cli << '\n'
+            dr << "  cli        " << pp << '\n'
                << "  version    " << ver;
         }
+
+        if (!unconf)
+          rs.assign<process_path> ("cli.path") = move (pp);
       }
 
       // Nothing else to do if we are unconfigured.
diff --git a/build2/cxx/init.cxx b/build2/cxx/init.cxx
index 14134f1..7d64975 100644
--- a/build2/cxx/init.cxx
+++ b/build2/cxx/init.cxx
@@ -121,16 +121,17 @@ namespace build2
 
           // Note: some overridable, some not.
           //
-          v.insert<path>     ("config.cxx",          true),
-          v.insert<strings>  ("config.cxx.poptions", true),
-          v.insert<strings>  ("config.cxx.coptions", true),
-          v.insert<strings>  ("config.cxx.loptions", true),
-          v.insert<strings>  ("config.cxx.libs",     true),
-
-          v.insert<strings>  ("cxx.poptions"),
-          v.insert<strings>  ("cxx.coptions"),
-          v.insert<strings>  ("cxx.loptions"),
-          v.insert<strings>  ("cxx.libs"),
+          v.insert<path>    ("config.cxx",          true),
+          v.insert<strings> ("config.cxx.poptions", true),
+          v.insert<strings> ("config.cxx.coptions", true),
+          v.insert<strings> ("config.cxx.loptions", true),
+          v.insert<strings> ("config.cxx.libs",     true),
+
+          v.insert<process_path> ("cxx.path"),
+          v.insert<strings>      ("cxx.poptions"),
+          v.insert<strings>      ("cxx.coptions"),
+          v.insert<strings>      ("cxx.loptions"),
+          v.insert<strings>      ("cxx.libs"),
 
           v["cc.poptions"],
           v["cc.coptions"],
diff --git a/build2/types b/build2/types
index e3aa1b1..df54860 100644
--- a/build2/types
+++ b/build2/types
@@ -127,8 +127,12 @@ namespace build2
   // <butl/fdstream>
   //
   using butl::process;
+  using butl::process_path;
   using butl::process_error;
 
+  ostream&
+  operator<< (ostream&, const process_path&); // Print as recall[@effect].
+
   using butl::ifdstream;
   using butl::ofdstream;
 }
diff --git a/build2/utility b/build2/utility
index ee12545..3fb47b7 100644
--- a/build2/utility
+++ b/build2/utility
@@ -84,11 +84,23 @@ namespace build2
   // diagnostics from the child process). Issue diagnostics and throw failed
   // in case of an error.
   //
+  process_path
+  run_search (const char*& args0);
+
+  process_path
+  run_search (const path&, bool init, const dir_path& fallback = dir_path ());
+
   process
-  start_run (const char* args[], bool error);
+  run_start (const process_path&, const char* args[], bool error);
+
+  inline process
+  run_start (const char* args[], bool error)
+  {
+    return run_start (run_search (args[0]), args, error);
+  }
 
   bool
-  finish_run (const char* args[], bool error, process&, const string&);
+  run_finish (const char* args[], bool error, process&, const string&);
 
   // Start the process as above and then call the specified function on each
   // trimmed line of the output until it returns a non-empty object T (tested
@@ -106,7 +118,8 @@ namespace build2
   //
   template <typename T>
   T
-  run (const char* args[],
+  run (const process_path&,
+       const char* args[],
        T (*) (string&),
        bool error = true,
        bool ignore_exit = false,
@@ -114,6 +127,19 @@ namespace build2
 
   template <typename T>
   inline T
+  run (const char* args[],
+       T (*f) (string&),
+       bool error = true,
+       bool ignore_exit = false,
+       sha256* checksum = nullptr)
+  {
+    return run<T> (run_search (args[0]), args, f, error, ignore_exit, checksum);
+  }
+
+  // run <prog>
+  //
+  template <typename T>
+  inline T
   run (const path& prog,
        T (*f) (string&),
        bool error = true,
@@ -126,6 +152,20 @@ namespace build2
 
   template <typename T>
   inline T
+  run (const process_path& pp,
+       T (*f) (string&),
+       bool error = true,
+       bool ignore_exit = false,
+       sha256* checksum = nullptr)
+  {
+    const char* args[] = {pp.recall_string (), nullptr};
+    return run<T> (pp, args, f, error, ignore_exit, checksum);
+  }
+
+  // run <prog> <arg>
+  //
+  template <typename T>
+  inline T
   run (const path& prog,
        const char* arg,
        T (*f) (string&),
@@ -137,6 +177,19 @@ namespace build2
     return run<T> (args, f, error, ignore_exit, checksum);
   }
 
+  template <typename T>
+  inline T
+  run (const process_path& pp,
+       const char* arg,
+       T (*f) (string&),
+       bool error = true,
+       bool ignore_exit = false,
+       sha256* checksum = nullptr)
+  {
+    const char* args[] = {pp.recall_string (), arg, nullptr};
+    return run<T> (pp, args, f, error, ignore_exit, checksum);
+  }
+
   // Empty string and path.
   //
   extern const std::string empty_string;
diff --git a/build2/utility.cxx b/build2/utility.cxx
index 8ebfe06..dc862c6 100644
--- a/build2/utility.cxx
+++ b/build2/utility.cxx
@@ -28,6 +28,17 @@ namespace build2
                   : p.representation ());
   }
 
+  ostream&
+  operator<< (ostream& os, const process_path& p)
+  {
+    os << p.recall_string ();
+
+    if (!p.effect.empty ())
+      os << '@' << p.effect.string (); // Suppress relative().
+
+    return os;
+  }
+
   //
   // <build2/utility>
   //
@@ -69,21 +80,47 @@ namespace build2
     return l;
   }
 
+  process_path
+  run_search (const char*& args0)
+  try
+  {
+    return process::path_search (args0);
+  }
+  catch (const process_error& e)
+  {
+    error << "unable to execute " << args0 << ": " << e.what ();
+    throw failed ();
+  }
+
+  process_path
+  run_search (const path& f, bool init, const dir_path& fallback)
+  try
+  {
+    return process::path_search (f, init, fallback);
+  }
+  catch (const process_error& e)
+  {
+    error << "unable execute " << f << ": " << e.what ();
+    throw failed ();
+  }
+
   process
-  start_run (const char* args[], bool err)
+  run_start (const process_path& pp, const char* args[], bool err)
   {
+    assert (args[0] == pp.recall_string ());
+
     if (verb >= 3)
       print_process (args);
 
     try
     {
-      return process (args, 0, -1, (err ? 2 : 1));
+      return process (pp, args, 0, -1, (err ? 2 : 1));
     }
     catch (const process_error& e)
     {
       if (e.child ())
       {
-        // Note: finish_run() expects this exact message.
+        // Note: run_finish() expects this exact message.
         //
         cerr << "unable to execute " << args[0] << ": " << e.what () << endl;
         exit (1);
@@ -96,7 +133,7 @@ namespace build2
   };
 
   bool
-  finish_run (const char* args[], bool err, process& pr, const string& l)
+  run_finish (const char* args[], bool err, process& pr, const string& l)
   try
   {
     if (pr.wait ())
@@ -111,7 +148,7 @@ namespace build2
     // want to let through is the inability to execute the program itself.
     // We cannot reserve a special exit status to signal this so we will
     // just have to compare the output. This particular situation will
-    // result in a single error line printed by start_run() above.
+    // result in a single error line printed by run_start() above.
     //
     if (l.compare (0, 18, "unable to execute ") == 0)
       fail << l;
diff --git a/build2/utility.txx b/build2/utility.txx
index 3e29db6..7256547 100644
--- a/build2/utility.txx
+++ b/build2/utility.txx
@@ -6,13 +6,14 @@ namespace build2
 {
   template <typename T>
   T
-  run (const char* args[],
+  run (const process_path& pp,
+       const char* args[],
        T (*f) (string&),
        bool err,
        bool ignore_exit,
        sha256* checksum)
   {
-    process pr (start_run (args, err));
+    process pr (run_start (pp, args, err));
 
     T r;
     string l; // Last line of output.
@@ -35,10 +36,10 @@ namespace build2
     }
     catch (const ifdstream::failure&)
     {
-      // Presumably the child process failed. Let finish_run() deal with that.
+      // Presumably the child process failed. Let run_finish() deal with that.
     }
 
-    if (!(finish_run (args, err, pr, l) || ignore_exit))
+    if (!(run_finish (args, err, pr, l) || ignore_exit))
       r = T ();
 
     return r;
diff --git a/build2/variable b/build2/variable
index d6be976..1248bd3 100644
--- a/build2/variable
+++ b/build2/variable
@@ -589,6 +589,28 @@ namespace build2
     static const build2::value_type value_type;
   };
 
+  // process_path
+  //
+  // Note that instances that we store always have non-empty recall and
+  // initial is its shallow copy.
+  //
+  template <>
+  struct value_traits<process_path>
+  {
+    static_assert (sizeof (process_path) <= value::size_, "insufficient space");
+
+    // This one is represented as a @-pair of names. As a result it cannot
+    // be stored in a container.
+    //
+    static process_path convert (name&&, name*);
+    static void assign (value&, process_path&&);
+    static int compare (const process_path&, const process_path&);
+    static bool empty (const process_path& x) {return x.empty ();}
+
+    static const char* const type_name;
+    static const build2::value_type value_type;
+  };
+
   // vector<T>
   //
   template <typename T>
diff --git a/build2/variable.cxx b/build2/variable.cxx
index eec0573..54b61b7 100644
--- a/build2/variable.cxx
+++ b/build2/variable.cxx
@@ -662,6 +662,104 @@ namespace build2
     &default_empty<name>
   };
 
+  // process_path value
+  //
+  process_path value_traits<process_path>::
+  convert (name&& n, name* r)
+  {
+    path rp (move (n.dir));
+    if (rp.empty ())
+      rp = path (move (n.value));
+    else
+      rp /= n.value;
+
+    path ep;
+    if (r != nullptr)
+    {
+      ep = move (r->dir);
+      if (ep.empty ())
+        ep = path (move (r->value));
+      else
+        ep /= r->value;
+    }
+
+    process_path pp (nullptr, move (rp), move (ep));
+    pp.initial = pp.recall.string ().c_str ();
+    return pp;
+  }
+
+  void
+  process_path_copy_ctor (value& l, const value& r, bool m)
+  {
+    const auto& rhs (r.as<process_path> ());
+
+    if (m)
+      new (&l.data_) process_path (move (const_cast<process_path&> (rhs)));
+    else
+    {
+      auto& lhs (
+        *new (&l.data_) process_path (
+          nullptr, path (rhs.recall), path (rhs.effect)));
+      lhs.initial = lhs.recall.string ().c_str ();
+    }
+  }
+
+  void
+  process_path_copy_assign (value& l, const value& r, bool m)
+  {
+    auto& lhs (l.as<process_path> ());
+    const auto& rhs (r.as<process_path> ());
+
+    if (m)
+      lhs = move (const_cast<process_path&> (rhs));
+    else
+    {
+      lhs.recall = rhs.recall;
+      lhs.effect = rhs.effect;
+      lhs.initial = lhs.recall.string ().c_str ();
+    }
+  }
+
+  static names_view
+  process_path_reverse (const value& v, names& s)
+  {
+    auto& pp (v.as<process_path> ());
+    s.reserve (pp.effect.empty () ? 1 : 2);
+
+    s.push_back (name (pp.recall.directory (),
+                       string (),
+                       pp.recall.leaf ().string ()));
+
+    if (!pp.effect.empty ())
+    {
+      s.back ().pair = '@';
+      s.push_back (name (pp.effect.directory (),
+                         string (),
+                         pp.effect.leaf ().string ()));
+    }
+
+    return s;
+  }
+
+  const char* const value_traits<process_path>::type_name = "process_path";
+
+  const value_type value_traits<process_path>::value_type
+  {
+    type_name,
+    sizeof (process_path),
+    nullptr,                            // No base.
+    &default_dtor<process_path>,
+    &process_path_copy_ctor,
+    &process_path_copy_assign,
+    &simple_assign<process_path, true>, // Allow empty values.
+    nullptr,                            // Append not supported.
+    nullptr,                            // Prepend not supported.
+    &process_path_reverse,
+    nullptr,                            // No cast (cast data_ directly).
+    &simple_compare<process_path>,
+    &default_empty<process_path>
+  };
+
   // variable_pool
   //
   const variable& variable_pool::
diff --git a/build2/variable.ixx b/build2/variable.ixx
index 4b699a6..393a796 100644
--- a/build2/variable.ixx
+++ b/build2/variable.ixx
@@ -476,6 +476,35 @@ namespace build2
     return l.compare (r);
   }
 
+  // process_path value
+  //
+  inline void value_traits<process_path>::
+  assign (value& v, process_path&& x)
+  {
+    // Convert the value to its "self-sufficient" form.
+    //
+    if (x.recall.empty ())
+      x.recall = path (x.initial);
+
+    x.initial = x.recall.string ().c_str ();
+
+    if (v)
+      v.as<process_path> () = move (x);
+    else
+      new (&v.data_) process_path (move (x));
+  }
+
+  inline int value_traits<process_path>::
+  compare (const process_path& x, const process_path& y)
+  {
+    int r (x.recall.compare (y.recall));
+
+    if (r == 0)
+      r = x.effect.compare (y.effect);
+
+    return r;
+  }
+
   // vector<T> value
   //
   template <typename T>