Merge commit '48f4317'

7 files changed, 527 insertions, 177 deletions

diff --git a/CC/EXPRESSIONS b/CC/EXPRESSIONS
index f1868d7..a520cde 100644
--- a/CC/EXPRESSIONS
+++ b/CC/EXPRESSIONS
@@ -115,7 +115,7 @@
   }
 , "defaults-base-provides":
   { "doc": ["Query list-provider from 'base' targets (last wins)"]
-  , "vars": ["provider"]
+  , "vars": ["provider", "default"]
   , "vars_doc":
     {"provider": ["The name of the list-provider in the provides map."]}
   , "imports": {"provider_list": ["./", "..", "field_provider_list"]}
@@ -125,6 +125,7 @@
     , "body":
       { "type": "foldl"
       , "var": "next"
+      , "start": {"type": "var", "name": "default", "default": []}
       , "accum_var": "curr"
       , "range": {"type": "CALL_EXPRESSION", "name": "provider_list"}
       , "body":
diff --git a/CC/IDE/RULES b/CC/IDE/RULES
deleted file mode 100644
index dc4b607..0000000
--- a/CC/IDE/RULES
+++ /dev/null
@@ -1,96 +0,0 @@
-{ "headers":
-  { "doc": ["Transitive public headers of C++ target"]
-  , "target_fields": ["proto", "deps"]
-  , "string_fields": ["stage"]
-  , "field_doc":
-    { "proto": ["The proto source files for creating cc bindings."]
-    , "deps": ["The targets to obtain the headers from."]
-    , "stage":
-      [ "The logical location of the header files. Individual directory"
-      , "components are joined with \"/\"."
-      ]
-    }
-  , "anonymous":
-    { "proto-deps":
-      { "target": "proto"
-      , "provider": "proto"
-      , "rule_map":
-        { "library": ["./", "../proto", "library"]
-        , "service library": ["./", "../proto", "service library"]
-        }
-      }
-    }
-  , "imports": {"runfiles_list": ["./", "../..", "field_runfiles_list"]}
-  , "expression":
-    { "type": "let*"
-    , "bindings":
-      [ [ "stage"
-        , { "type": "join"
-          , "separator": "/"
-          , "$1": {"type": "FIELD", "name": "stage"}
-          }
-        ]
-      , [ "artifacts"
-        , { "type": "to_subdir"
-          , "subdir": {"type": "var", "name": "stage"}
-          , "$1":
-            { "type": "map_union"
-            , "$1":
-              { "type": "++"
-              , "$1":
-                [ { "type": "let*"
-                  , "bindings": [["fieldname", "proto-deps"]]
-                  , "body":
-                    {"type": "CALL_EXPRESSION", "name": "runfiles_list"}
-                  }
-                , { "type": "foreach"
-                  , "var": "x"
-                  , "range": {"type": "FIELD", "name": "proto-deps"}
-                  , "body":
-                    { "type": "DEP_PROVIDES"
-                    , "provider": "compile-deps"
-                    , "dep": {"type": "var", "name": "x"}
-                    , "default":
-                      { "type": "fail"
-                      , "msg":
-                        [ "Expected a library target, but got:"
-                        , {"type": "var", "name": "x"}
-                        ]
-                      }
-                    }
-                  }
-                , { "type": "let*"
-                  , "bindings": [["fieldname", "deps"]]
-                  , "body":
-                    {"type": "CALL_EXPRESSION", "name": "runfiles_list"}
-                  }
-                , { "type": "foreach"
-                  , "var": "x"
-                  , "range": {"type": "FIELD", "name": "deps"}
-                  , "body":
-                    { "type": "DEP_PROVIDES"
-                    , "provider": "compile-deps"
-                    , "dep": {"type": "var", "name": "x"}
-                    , "default":
-                      { "type": "fail"
-                      , "msg":
-                        [ "Expected a library target, but got:"
-                        , {"type": "var", "name": "x"}
-                        ]
-                      }
-                    }
-                  }
-                ]
-              }
-            }
-          }
-        ]
-      ]
-    , "body":
-      { "type": "RESULT"
-      , "artifacts": {"type": "var", "name": "artifacts"}
-      , "runfiles": {"type": "var", "name": "artifacts"}
-      }
-    }
-  }
-}
diff --git a/CC/pkgconfig/EXPRESSIONS b/CC/pkgconfig/EXPRESSIONS
new file mode 100644
index 0000000..c770421
--- /dev/null
+++ b/CC/pkgconfig/EXPRESSIONS
@@ -0,0 +1,136 @@
+{ "pkgconfig result":
+  { "vars": ["ENV", "name", "args", "stage"]
+  , "imports": {"default-ENV": ["./", "..", "default-ENV"]}
+  , "expression":
+    { "type": "let*"
+    , "bindings":
+      [ [ "ENV"
+        , { "type": "map_union"
+          , "$1":
+            { "type": "++"
+            , "$1":
+              [ {"type": "CALL_EXPRESSION", "name": "default-ENV"}
+              , [ { "type": "var"
+                  , "name": "ENV"
+                  , "default": {"type": "empty_map"}
+                  }
+                ]
+              ]
+            }
+          }
+        ]
+      , [ "cflags-filename"
+        , {"type": "join", "$1": [{"type": "var", "name": "name"}, ".cflags"]}
+        ]
+      , [ "cflags-files"
+        , { "type": "to_subdir"
+          , "subdir": {"type": "var", "name": "stage"}
+          , "$1":
+            { "type": "ACTION"
+            , "inputs": {"type": "empty_map"}
+            , "cmd":
+              [ "/bin/sh"
+              , "-c"
+              , { "type": "join"
+                , "separator": " "
+                , "$1":
+                  { "type": "++"
+                  , "$1":
+                    [ ["pkg-config"]
+                    , [ { "type": "join_cmd"
+                        , "$1":
+                          { "type": "++"
+                          , "$1":
+                            [ {"type": "var", "name": "args", "default": []}
+                            , ["--cflags", {"type": "var", "name": "name"}]
+                            ]
+                          }
+                        }
+                      ]
+                    , [">"]
+                    , [ { "type": "join_cmd"
+                        , "$1": {"type": "var", "name": "cflags-filename"}
+                        }
+                      ]
+                    ]
+                  }
+                }
+              ]
+            , "env": {"type": "var", "name": "ENV"}
+            , "outs": [{"type": "var", "name": "cflags-filename"}]
+            }
+          }
+        ]
+      , [ "compile-args"
+        , { "type": "foreach_map"
+          , "var_key": "flag-file"
+          , "range": {"type": "var", "name": "cflags-files"}
+          , "body":
+            {"type": "join", "$1": ["@", {"type": "var", "name": "flag-file"}]}
+          }
+        ]
+      , [ "ldflags-filename"
+        , {"type": "join", "$1": [{"type": "var", "name": "name"}, ".ldflags"]}
+        ]
+      , [ "ldflags-files"
+        , { "type": "to_subdir"
+          , "subdir": {"type": "var", "name": "stage"}
+          , "$1":
+            { "type": "ACTION"
+            , "inputs": {"type": "empty_map"}
+            , "cmd":
+              [ "/bin/sh"
+              , "-c"
+              , { "type": "join"
+                , "separator": " "
+                , "$1":
+                  { "type": "++"
+                  , "$1":
+                    [ ["pkg-config"]
+                    , [ { "type": "join_cmd"
+                        , "$1":
+                          { "type": "++"
+                          , "$1":
+                            [ {"type": "var", "name": "args", "default": []}
+                            , ["--libs", {"type": "var", "name": "name"}]
+                            ]
+                          }
+                        }
+                      ]
+                    , [">"]
+                    , [ { "type": "join_cmd"
+                        , "$1": {"type": "var", "name": "ldflags-filename"}
+                        }
+                      ]
+                    ]
+                  }
+                }
+              ]
+            , "env": {"type": "var", "name": "ENV"}
+            , "outs": [{"type": "var", "name": "ldflags-filename"}]
+            }
+          }
+        ]
+      , [ "link-args"
+        , { "type": "foreach_map"
+          , "var_key": "flag-file"
+          , "range": {"type": "var", "name": "ldflags-files"}
+          , "body":
+            {"type": "join", "$1": ["@", {"type": "var", "name": "flag-file"}]}
+          }
+        ]
+      , ["package", {"type": "env", "vars": ["cflags-files", "ldflags-files"]}]
+      , ["compile-deps", {"type": "empty_map"}]
+      , ["link-deps", {"type": "empty_map"}]
+      ]
+    , "body":
+      { "type": "RESULT"
+      , "provides":
+        { "type": "env"
+        , "vars":
+          ["compile-deps", "compile-args", "link-deps", "link-args", "package"]
+        }
+      }
+    }
+  }
+}
diff --git a/CC/pkgconfig/RULES b/CC/pkgconfig/RULES
new file mode 100644
index 0000000..a6f6ce8
--- /dev/null
+++ b/CC/pkgconfig/RULES
@@ -0,0 +1,52 @@
+{ "system_library":
+  { "doc": ["A system library via pkg-config"]
+  , "string_fields": ["name", "args", "stage"]
+  , "implicit": {"defaults": [["./", "..", "defaults"]]}
+  , "config_vars": ["PKG_CONFIG_ARGS", "ENV"]
+  , "field_doc":
+    { "name": ["The pkg-config name of the library."]
+    , "args":
+      [ "Additional pkg-config arguments (e.g., \"--define-prefix\" or"
+      , "\"--static\"), appended to the config variable \"PKG_CONFIG_ARGS\"."
+      ]
+    , "stage": ["The stage of the internally created flag files."]
+    }
+  , "config_doc":
+    { "PKG_CONFIG_ARGS":
+      [ "Additional pkg-config arguments (e.g., \"--define-prefix\" or"
+      , "\"--static\")."
+      ]
+    , "ENV":
+      [ "The environment for any action generated. May contain colon-separated"
+      , "\"PKG_CONFIG_PATH\" for looking up pkg-config files."
+      ]
+    }
+  , "imports": {"pkgconfig result": "pkgconfig result"}
+  , "expression":
+    { "type": "let*"
+    , "bindings":
+      [ [ "name"
+        , { "type": "assert_non_empty"
+          , "msg": "system_library requires non-empty name"
+          , "$1": {"type": "join", "$1": {"type": "FIELD", "name": "name"}}
+          }
+        ]
+      , [ "args"
+        , { "type": "++"
+          , "$1":
+            [ {"type": "var", "name": "PKG_CONFIG_ARGS", "default": []}
+            , {"type": "FIELD", "name": "args"}
+            ]
+          }
+        ]
+      , [ "stage"
+        , { "type": "join"
+          , "separator": "/"
+          , "$1": {"type": "FIELD", "name": "stage"}
+          }
+        ]
+      ]
+    , "body": {"type": "CALL_EXPRESSION", "name": "pkgconfig result"}
+    }
+  }
+}
diff --git a/CC/proto/EXPRESSIONS b/CC/proto/EXPRESSIONS
index 1ab17a5..d2705f1 100644
--- a/CC/proto/EXPRESSIONS
+++ b/CC/proto/EXPRESSIONS
@@ -1,4 +1,81 @@
-{ "protoc-deps":
+{ "default-PROTOC":
+  { "vars": ["defaults-transition"]
+  , "imports": {"list_provider": ["./", "../..", "field_list_provider"]}
+  , "expression":
+    { "type": "let*"
+    , "bindings":
+      [ ["fieldname", "proto-defaults"]
+      , ["provider", "PROTOC"]
+      , [ "transition"
+        , {"type": "var", "name": "defaults-transition", "default": null}
+        ]
+      ]
+    , "body": {"type": "CALL_EXPRESSION", "name": "list_provider"}
+    }
+  }
+, "default-LDFLAGS":
+  { "vars": ["defaults-transition"]
+  , "imports": {"list_provider": ["./", "../..", "field_list_provider"]}
+  , "expression":
+    { "type": "let*"
+    , "bindings":
+      [ ["fieldname", "proto-defaults"]
+      , ["provider", "LDFLAGS"]
+      , [ "transition"
+        , {"type": "var", "name": "defaults-transition", "default": null}
+        ]
+      ]
+    , "body": {"type": "CALL_EXPRESSION", "name": "list_provider"}
+    }
+  }
+, "default-GRPC_PLUGIN":
+  { "vars": ["defaults-transition"]
+  , "imports": {"list_provider": ["./", "../..", "field_list_provider"]}
+  , "expression":
+    { "type": "let*"
+    , "bindings":
+      [ ["fieldname", "proto-defaults"]
+      , ["provider", "GRPC_PLUGIN"]
+      , [ "transition"
+        , {"type": "var", "name": "defaults-transition", "default": null}
+        ]
+      ]
+    , "body": {"type": "CALL_EXPRESSION", "name": "list_provider"}
+    }
+  }
+, "default-ENV":
+  { "vars": ["defaults-transition"]
+  , "imports": {"map_provider": ["./", "../..", "field_map_provider"]}
+  , "expression":
+    { "type": "let*"
+    , "bindings":
+      [ ["fieldname", "proto-defaults"]
+      , ["provider", "ENV"]
+      , [ "transition"
+        , {"type": "var", "name": "defaults-transition", "default": null}
+        ]
+      , ["default", {"type": "empty_map"}]
+      ]
+    , "body": {"type": "CALL_EXPRESSION", "name": "map_provider"}
+    }
+  }
+, "default-TOOLCHAIN":
+  { "vars": ["defaults-transition"]
+  , "imports": {"map_provider": ["./", "../..", "field_map_provider"]}
+  , "expression":
+    { "type": "let*"
+    , "bindings":
+      [ ["fieldname", "proto-defaults"]
+      , ["provider", "TOOLCHAIN"]
+      , [ "transition"
+        , {"type": "var", "name": "defaults-transition", "default": null}
+        ]
+      , ["default", {"type": "empty_map"}]
+      ]
+    , "body": {"type": "CALL_EXPRESSION", "name": "map_provider"}
+    }
+  }
+, "protoc-deps":
   { "imports": {"map_provider": ["./", "../..", "field_map_provider"]}
   , "expression":
     { "type": "let*"
@@ -16,57 +93,66 @@
     , "name"
     , "stage"
     , "service support"
-    , "deps-transition"
     , "public-fieldnames"
     , "private-fieldnames"
     ]
   , "imports":
     { "stage": ["", "stage_singleton_field"]
     , "result": ["./", "..", "lib result"]
-    , "artifacts": ["./", "../..", "field_artifacts"]
+    , "runfiles": ["./", "../..", "field_runfiles"]
     , "artifacts_list": ["./", "../..", "field_artifacts_list"]
     , "protoc-deps": "protoc-deps"
+    , "default-PROTOC": "default-PROTOC"
+    , "default-LDFLAGS": "default-LDFLAGS"
+    , "default-GRPC_PLUGIN": "default-GRPC_PLUGIN"
+    , "default-ENV": "default-ENV"
+    , "default-TOOLCHAIN": "default-TOOLCHAIN"
     }
   , "expression":
     { "type": "let*"
     , "bindings":
       [ ["pure C", false]
-      , [ "protoc"
-        , { "type": "let*"
-          , "bindings":
-            [ ["fieldname", "protoc"]
-            , ["transition", {"type": "var", "name": "deps-transition"}]
-            , ["location", "protoc"]
-            ]
-          , "body": {"type": "CALL_EXPRESSION", "name": "stage"}
-          }
-        ]
-      , [ "grpc_cpp_plugin"
+      , ["TOOLCHAIN_DIR", "toolchain"]
+      , ["TOOLCHAIN", {"type": "CALL_EXPRESSION", "name": "default-TOOLCHAIN"}]
+      , [ "TOOLCHAIN"
         , { "type": "if"
-          , "cond": {"type": "var", "name": "service support"}
+          , "cond": {"type": "var", "name": "TOOLCHAIN"}
           , "then":
-            { "type": "let*"
-            , "bindings":
-              [ ["fieldname", "grpc_cpp_plugin"]
-              , ["transition", {"type": "var", "name": "deps-transition"}]
-              , ["location", "grpc_cpp_plugin"]
+            { "type": "to_subdir"
+            , "subdir": {"type": "var", "name": "TOOLCHAIN_DIR"}
+            , "$1": {"type": "var", "name": "TOOLCHAIN"}
+            }
+          }
+        ]
+      , [ "PROTOC"
+        , { "type": "join"
+          , "$1":
+            { "type": "++"
+            , "$1":
+              [ { "type": "if"
+                , "cond": {"type": "var", "name": "TOOLCHAIN"}
+                , "then": ["./", {"type": "var", "name": "TOOLCHAIN_DIR"}, "/"]
+                }
+              , {"type": "CALL_EXPRESSION", "name": "default-PROTOC"}
               ]
-            , "body": {"type": "CALL_EXPRESSION", "name": "stage"}
             }
-          , "else": {"type": "empty_map"}
           }
         ]
-      , ["protoc-deps", {"type": "CALL_EXPRESSION", "name": "protoc-deps"}]
-      , [ "proto deps"
-        , { "type": "to_subdir"
-          , "subdir": "work"
+      , [ "GRPC_PLUGIN"
+        , { "type": "join"
           , "$1":
-            { "type": "let*"
-            , "bindings": [["fieldname", "well_known_protos"]]
-            , "body": {"type": "CALL_EXPRESSION", "name": "artifacts"}
+            { "type": "++"
+            , "$1":
+              [ { "type": "if"
+                , "cond": {"type": "var", "name": "TOOLCHAIN"}
+                , "then": ["./", {"type": "var", "name": "TOOLCHAIN_DIR"}, "/"]
+                }
+              , {"type": "CALL_EXPRESSION", "name": "default-GRPC_PLUGIN"}
+              ]
             }
           }
         ]
+      , ["protoc-deps", {"type": "CALL_EXPRESSION", "name": "protoc-deps"}]
       , [ "proto srcs"
         , { "type": "disjoint_map_union"
           , "msg": "Sources may not conflict"
@@ -139,12 +225,20 @@
       , [ "cmd"
         , { "type": "++"
           , "$1":
-            [ ["./protoc", "--proto_path=work", "--cpp_out=work"]
+            [ [ {"type": "var", "name": "PROTOC"}
+              , "--proto_path=work"
+              , "--cpp_out=work"
+              ]
             , { "type": "if"
               , "cond": {"type": "var", "name": "service support"}
               , "then":
                 [ "--grpc_out=work"
-                , "--plugin=protoc-gen-grpc=./grpc_cpp_plugin"
+                , { "type": "join"
+                  , "$1":
+                    [ "--plugin=protoc-gen-grpc="
+                    , {"type": "var", "name": "GRPC_PLUGIN"}
+                    ]
+                  }
                 ]
               , "else": []
               }
@@ -158,9 +252,7 @@
             { "type": "map_union"
             , "$1":
               [ {"type": "var", "name": "staged all proto srcs"}
-              , {"type": "var", "name": "protoc"}
-              , {"type": "var", "name": "grpc_cpp_plugin"}
-              , {"type": "var", "name": "proto deps"}
+              , {"type": "var", "name": "TOOLCHAIN"}
               ]
             }
           , "outs": {"type": "var", "name": "outs"}
@@ -299,8 +391,10 @@
           }
         ]
       , ["cflags", []]
-      , ["private-cflags", ["-Wno-sign-conversion", "-Wno-unused-function"]]
-      , ["private-ldflags", []]
+      , ["private-cflags", []]
+      , [ "private-ldflags"
+        , {"type": "CALL_EXPRESSION", "name": "default-LDFLAGS"}
+        ]
       ]
     , "body": {"type": "CALL_EXPRESSION", "name": "result"}
     }
diff --git a/CC/proto/RULES b/CC/proto/RULES
index 39d342f..97b4367 100644
--- a/CC/proto/RULES
+++ b/CC/proto/RULES
@@ -1,4 +1,186 @@
-{ "library":
+{ "defaults":
+  { "doc":
+    [ "A rule to provide protoc/GRPC defaults."
+    , "Used to implement [\"CC/proto\", \"defaults\"] for CC proto libraries"
+    , "and [\"CC/proto\", \"service defaults\"] for CC proto service libraries"
+    , "(GRPC)."
+    ]
+  , "target_fields": ["base", "toolchain", "deps"]
+  , "string_fields":
+    ["PROTOC", "LDFLAGS", "ADD_LDFLAGS", "GRPC_PLUGIN", "PATH"]
+  , "config_vars": ["ARCH", "HOST_ARCH"]
+  , "field_doc":
+    { "base":
+      [ "Other targets (using the same rule) to inherit values from. If"
+      , "multiple targets are specified, for values that are overwritten (see"
+      , "documentation of other fields) the last specified value wins."
+      ]
+    , "toolchain":
+      [ "Optional toolchain directory. A collection of artifacts that provide"
+      , "the protobuf compiler and the GRPC plugin (if needed). Note that only"
+      , "artifacts of the specified targets are considered (no runfiles etc.)."
+      , "Specifying this field overlays artifacts from \"base\"."
+      ]
+    , "deps":
+      [ "Optional CC libraries the resulting CC proto libraries implicitly"
+      , "depend on. Those are typically \"libprotobuf\" for CC proto libraries"
+      , "and \"libgrpc++\" for CC proto service libraries. Specifying this"
+      , "field extends dependencies from \"base\"."
+      ]
+    , "PROTOC":
+      [ "The proto compiler. If \"toolchain\" is empty, this field's value is"
+      , "considered the proto compiler name that is looked up in \"PATH\". If"
+      , "\"toolchain\" is non-empty, this field's value is assumed to be the"
+      , "relative path to the proto compiler in \"toolchain\". Specifying this"
+      , "field overwrites values from \"base\"."
+      ]
+    , "GRPC_PLUGIN":
+      [ "The GRPC plugin for the proto compiler. If \"toolchain\" is empty,"
+      , "this field's value is considered to be the absolute system path to the"
+      , "plugin. If \"toolchain\" is non-empty, this field's value is assumed"
+      , "to be the relative path to the plugin in \"toolchain\". Specifying"
+      , "this field overwrites values from \"base\"."
+      ]
+    , "LDFLAGS":
+      [ "Linker flags for linking the final CC library. Specifying this field"
+      , "overwrites values from \"base\"."
+      ]
+    , "ADD_LDFLAGS":
+      [ "Additional linker flags for linking the final CC library. Specifying"
+      , "this field extends values from \"base\"."
+      ]
+    , "PATH":
+      [ "Path for looking up the proto compiler. Individual paths are joined"
+      , "with \":\"."
+      ]
+    }
+  , "imports":
+    { "base-provides": ["./", "..", "defaults-base-provides"]
+    , "artifacts": ["", "field_artifacts"]
+    , "compile-deps": ["CC", "compile-deps"]
+    , "compile-args-deps": ["CC", "compile-args-deps"]
+    , "link-deps": ["CC", "link-deps"]
+    , "link-args-deps": ["CC", "link-args-deps"]
+    , "cflags-files-deps": ["CC", "cflags-files-deps"]
+    , "ldflags-files-deps": ["CC", "ldflags-files-deps"]
+    , "for host": ["transitions", "for host"]
+    }
+  , "config_transitions":
+    {"toolchain": [{"type": "CALL_EXPRESSION", "name": "for host"}]}
+  , "expression":
+    { "type": "let*"
+    , "bindings":
+      [ ["PROTOC", {"type": "FIELD", "name": "PROTOC"}]
+      , ["LDFLAGS", {"type": "FIELD", "name": "LDFLAGS"}]
+      , ["GRPC_PLUGIN", {"type": "FIELD", "name": "GRPC_PLUGIN"}]
+      , ["PATH", {"type": "FIELD", "name": "PATH"}]
+      , ["provider", "PROTOC"]
+      , [ "PROTOC"
+        , { "type": "if"
+          , "cond": {"type": "var", "name": "PROTOC"}
+          , "then": {"type": "var", "name": "PROTOC"}
+          , "else": {"type": "CALL_EXPRESSION", "name": "base-provides"}
+          }
+        ]
+      , ["provider", "LDFLAGS"]
+      , [ "LDFLAGS"
+        , { "type": "if"
+          , "cond": {"type": "var", "name": "LDFLAGS"}
+          , "then": {"type": "var", "name": "LDFLAGS"}
+          , "else": {"type": "CALL_EXPRESSION", "name": "base-provides"}
+          }
+        ]
+      , ["provider", "GRPC_PLUGIN"]
+      , [ "GRPC_PLUGIN"
+        , { "type": "if"
+          , "cond": {"type": "var", "name": "GRPC_PLUGIN"}
+          , "then": {"type": "var", "name": "GRPC_PLUGIN"}
+          , "else": {"type": "CALL_EXPRESSION", "name": "base-provides"}
+          }
+        ]
+      , ["provider", "ENV"]
+      , [ "ENV"
+        , { "type": "if"
+          , "cond": {"type": "var", "name": "PATH"}
+          , "then":
+            { "type": "singleton_map"
+            , "key": "PATH"
+            , "value":
+              { "type": "join"
+              , "separator": ":"
+              , "$1": {"type": "var", "name": "PATH"}
+              }
+            }
+          , "else": {"type": "CALL_EXPRESSION", "name": "base-provides"}
+          }
+        ]
+      , ["provider", "TOOLCHAIN"]
+      , ["default", {"type": "empty_map"}]
+      , [ "TOOLCHAIN"
+        , { "type": "map_union"
+          , "$1":
+            [ {"type": "CALL_EXPRESSION", "name": "base-provides"}
+            , { "type": "if"
+              , "cond": {"type": "FIELD", "name": "toolchain"}
+              , "then":
+                { "type": "let*"
+                , "bindings":
+                  [ ["fieldname", "toolchain"]
+                  , [ "transition"
+                    , {"type": "CALL_EXPRESSION", "name": "for host"}
+                    ]
+                  ]
+                , "body": {"type": "CALL_EXPRESSION", "name": "artifacts"}
+                }
+              , "else": {"type": "empty_map"}
+              }
+            ]
+          }
+        ]
+      , [ "LDFLAGS"
+        , { "type": "++"
+          , "$1":
+            [ {"type": "var", "name": "LDFLAGS"}
+            , {"type": "FIELD", "name": "ADD_LDFLAGS"}
+            ]
+          }
+        ]
+      , ["deps-fieldnames", ["base", "deps"]]
+      , ["compile-deps", {"type": "CALL_EXPRESSION", "name": "compile-deps"}]
+      , [ "compile-args"
+        , {"type": "CALL_EXPRESSION", "name": "compile-args-deps"}
+        ]
+      , ["link-deps", {"type": "CALL_EXPRESSION", "name": "link-deps"}]
+      , ["link-args", {"type": "CALL_EXPRESSION", "name": "link-args-deps"}]
+      , [ "cflags-files"
+        , {"type": "CALL_EXPRESSION", "name": "cflags-files-deps"}
+        ]
+      , [ "ldflags-files"
+        , {"type": "CALL_EXPRESSION", "name": "ldflags-files-deps"}
+        ]
+      , ["package", {"type": "env", "vars": ["cflags-files", "ldflags-files"]}]
+      ]
+    , "body":
+      { "type": "RESULT"
+      , "provides":
+        { "type": "env"
+        , "vars":
+          [ "PROTOC"
+          , "LDFLAGS"
+          , "GRPC_PLUGIN"
+          , "ENV"
+          , "TOOLCHAIN"
+          , "compile-deps"
+          , "compile-args"
+          , "link-deps"
+          , "link-args"
+          , "package"
+          ]
+        }
+      }
+    }
+  }
+, "library":
   { "doc":
     [ "A library C++ library, generated from proto files."
     , ""
@@ -7,20 +189,10 @@
     ]
   , "string_fields": ["name", "stage"]
   , "target_fields": ["srcs", "deps"]
-  , "config_vars":
-    ["OS", "ARCH", "HOST_ARCH", "CXX", "CXXFLAGS", "ADD_CXXFLAGS", "AR", "ENV"]
+  , "config_vars": ["CXX", "CXXFLAGS", "ADD_CXXFLAGS", "AR", "ENV"]
   , "implicit":
-    { "protoc": [["@", "protoc", "", "protoc"]]
-    , "defaults": [["./", "..", "defaults"]]
-    , "proto-deps": [["@", "protoc", "", "C++ runtime"]]
-    , "well_known_protos": [["@", "protoc", "", "well_known_protos"]]
-    }
-  , "imports":
-    { "protoc-compile": "protoc-compile"
-    , "host transition": ["transitions", "for host"]
-    }
-  , "config_transitions":
-    {"protoc": [{"type": "CALL_EXPRESSION", "name": "host transition"}]}
+    {"defaults": [["./", "..", "defaults"]], "proto-defaults": ["defaults"]}
+  , "imports": {"protoc-compile": "protoc-compile"}
   , "expression":
     { "type": "let*"
     , "bindings":
@@ -31,11 +203,8 @@
           , "$1": {"type": "FIELD", "name": "stage"}
           }
         ]
-      , [ "deps-transition"
-        , {"type": "CALL_EXPRESSION", "name": "host transition"}
-        ]
-      , ["public-fieldnames", ["deps", "proto-deps"]]
-      , ["private-fieldnames", ["deps", "proto-deps"]]
+      , ["public-fieldnames", ["deps"]]
+      , ["private-fieldnames", ["deps", "proto-defaults"]]
       ]
     , "body": {"type": "CALL_EXPRESSION", "name": "protoc-compile"}
     }
@@ -49,28 +218,12 @@
     ]
   , "string_fields": ["name", "stage"]
   , "target_fields": ["srcs", "deps"]
-  , "config_vars":
-    ["OS", "ARCH", "HOST_ARCH", "CXX", "CXXFLAGS", "ADD_CXXFLAGS", "AR", "ENV"]
+  , "config_vars": ["CXX", "CXXFLAGS", "ADD_CXXFLAGS", "AR", "ENV"]
   , "implicit":
-    { "protoc": [["@", "protoc", "", "protoc"]]
-    , "grpc_cpp_plugin": [["@", "grpc", "src/compiler", "grpc_cpp_plugin"]]
-    , "defaults": [["./", "..", "defaults"]]
-    , "proto-deps":
-      [ ["@", "grpc", "", "grpc++_codegen_proto"]
-      , ["@", "grpc", "", "grpc++_codegen_base_src"]
-      , ["@", "protoc", "", "C++ runtime"]
-      ]
-    , "well_known_protos": [["@", "protoc", "", "well_known_protos"]]
-    }
-  , "imports":
-    { "protoc-compile": "protoc-compile"
-    , "host transition": ["transitions", "for host"]
-    }
-  , "config_transitions":
-    { "protoc": [{"type": "CALL_EXPRESSION", "name": "host transition"}]
-    , "grpc_cpp_plugin":
-      [{"type": "CALL_EXPRESSION", "name": "host transition"}]
+    { "defaults": [["./", "..", "defaults"]]
+    , "proto-defaults": ["service defaults"]
     }
+  , "imports": {"protoc-compile": "protoc-compile"}
   , "expression":
     { "type": "let*"
     , "bindings":
@@ -82,11 +235,8 @@
           , "$1": {"type": "FIELD", "name": "stage"}
           }
         ]
-      , [ "deps-transition"
-        , {"type": "CALL_EXPRESSION", "name": "host transition"}
-        ]
-      , ["public-fieldnames", ["deps", "proto-deps"]]
-      , ["private-fieldnames", ["deps", "proto-deps"]]
+      , ["public-fieldnames", ["deps", "proto-defaults"]]
+      , ["private-fieldnames", ["deps", "proto-defaults"]]
       ]
     , "body": {"type": "CALL_EXPRESSION", "name": "protoc-compile"}
     }
diff --git a/CC/proto/TARGETS b/CC/proto/TARGETS
new file mode 100644
index 0000000..45ef759
--- /dev/null
+++ b/CC/proto/TARGETS
@@ -0,0 +1,13 @@
+{ "defaults":
+  { "type": ["CC/proto", "defaults"]
+  , "PROTOC": ["protoc"]
+  , "LDFLAGS": ["-lprotobuf"]
+  , "PATH": ["/bin", "/usr/bin"]
+  }
+, "service defaults":
+  { "type": ["CC/proto", "defaults"]
+  , "base": ["defaults"]
+  , "GRPC_PLUGIN": ["/usr/bin/grpc_cpp_plugin"]
+  , "ADD_LDFLAGS": ["-lgrpc++", "-lgrpc", "-lgpr"]
+  }
+}