compiler: Add -fgo-relative-import-path.

	* lang.opt (-fgo-relative-import-path): New option.
	* go-lang.c (go_relative_import_path): New static variable.
	(go_langhook_init): Pass go_relative_import_path to
	go_create_gogo.
	(go_langhook_handle_option): Handle -fgo-relative-import-path.
	* go-c.h (go_create_gogo): Update declaration.
	* gccgo.texi (Invoking gccgo): Document
	-fgo-relative-import-path.

From-SVN: r193008

gcc/go/ChangeLog

+2012-10-30  Ian Lance Taylor  <iant@google.com>
+
+	* lang.opt (-fgo-relative-import-path): New option.
+	* go-lang.c (go_relative_import_path): New static variable.
+	(go_langhook_init): Pass go_relative_import_path to
+	go_create_gogo.
+	(go_langhook_handle_option): Handle -fgo-relative-import-path.
+	* go-c.h (go_create_gogo): Update declaration.
+	* gccgo.texi (Invoking gccgo): Document
+	-fgo-relative-import-path.
+
 2012-09-17  Ian Lance Taylor  <iant@google.com>
 
 	* config-lang.in (target_libs): Add target-libbacktrace.

gcc/go/gccgo.texi

@@ -184,6 +184,12 @@ Using either @option{-fgo-pkgpath} or @option{-fgo-prefix} disables
 the special treatment of the @code{main} package and permits that
 package to be imported like any other.
 
+@item -fgo-relative-import-path=@var{dir}
+@cindex @option{-fgo-relative-import-path}
+A relative import is an import that starts with @file{./} or
+@file{../}.  If this option is used, @command{gccgo} will use
+@var{dir} as a prefix for the relative import when searching for it.
+
 @item -frequire-return-statement
 @itemx -fno-require-return-statement
 @cindex @option{-frequire-return-statement}

gcc/go/go-c.h

@@ -33,7 +33,8 @@ extern int go_enable_optimize (const char*);
 extern void go_add_search_path (const char*);
 
 extern void go_create_gogo (int int_type_size, int pointer_size,
-			    const char* pkgpath, const char *prefix);
+			    const char* pkgpath, const char *prefix,
+			    const char *relative_import_path);
 
 extern void go_parse_input_files (const char**, unsigned int,
 				  bool only_check_syntax,

gcc/go/go-lang.c

@@ -85,6 +85,7 @@ struct GTY(()) language_function
 
 static const char *go_pkgpath = NULL;
 static const char *go_prefix = NULL;
+static const char *go_relative_import_path = NULL;
 
 /* Language hooks.  */
 
@@ -101,7 +102,8 @@ go_langhook_init (void)
      to, e.g., unsigned_char_type_node) but before calling
      build_common_builtin_nodes (because it calls, indirectly,
      go_type_for_size).  */
-  go_create_gogo (INT_TYPE_SIZE, POINTER_SIZE, go_pkgpath, go_prefix);
+  go_create_gogo (INT_TYPE_SIZE, POINTER_SIZE, go_pkgpath, go_prefix,
+		  go_relative_import_path);
 
   build_common_builtin_nodes ();
 
@@ -240,6 +242,10 @@ go_langhook_handle_option (
       go_prefix = arg;
       break;
 
+    case OPT_fgo_relative_import_path_:
+      go_relative_import_path = arg;
+      break;
+
     default:
       /* Just return 1 to indicate that the option is valid.  */
       break;

gcc/go/gofrontend/go.cc

@@ -21,7 +21,7 @@ static Gogo* gogo;
 GO_EXTERN_C
 void
 go_create_gogo(int int_type_size, int pointer_size, const char *pkgpath,
-	       const char *prefix)
+	       const char *prefix, const char *relative_import_path)
 {
   go_assert(::gogo == NULL);
   Linemap* linemap = go_get_linemap();
@@ -32,6 +32,9 @@ go_create_gogo(int int_type_size, int pointer_size, const char *pkgpath,
   else if (prefix != NULL)
     ::gogo->set_prefix(prefix);
 
+  if (relative_import_path != NULL)
+    ::gogo->set_relative_import_path(relative_import_path);
+
   // FIXME: This should be in the gcc dependent code.
   ::gogo->define_builtin_function_trees();
 }

gcc/go/gofrontend/gogo.cc

@@ -44,6 +44,7 @@ Gogo::Gogo(Backend* backend, Linemap* linemap, int int_type_size,
     pkgpath_set_(false),
     pkgpath_from_option_(false),
     prefix_from_option_(false),
+    relative_import_path_(),
     verify_types_(),
     interface_types_(),
     specific_type_functions_(),
@@ -477,7 +478,8 @@ Gogo::import_package(const std::string& filename,
       return;
     }
 
-  Import::Stream* stream = Import::open_package(filename, location);
+  Import::Stream* stream = Import::open_package(filename, location,
+						this->relative_import_path_);
   if (stream == NULL)
     {
       error_at(location, "import file %qs not found", filename.c_str());

gcc/go/gofrontend/gogo.h

@@ -206,6 +206,17 @@ class Gogo
   pkgpath_from_option() const
   { return this->pkgpath_from_option_; }
 
+  // Return the relative import path as set from the command line.
+  // Returns an empty string if it was not set.
+  const std::string&
+  relative_import_path() const
+  { return this->relative_import_path_; }
+
+  // Set the relative import path from a command line option.
+  void
+  set_relative_import_path(const std::string& s)
+  {this->relative_import_path_ = s; }
+
   // Return the priority to use for the package we are compiling.
   // This is two more than the largest priority of any package we
   // import.
@@ -732,6 +743,9 @@ class Gogo
   bool pkgpath_from_option_;
   // Whether an explicit prefix was set by -fgo-prefix.
   bool prefix_from_option_;
+  // The relative import path, from the -fgo-relative-import-path
+  // option.
+  std::string relative_import_path_;
   // A list of types to verify.
   std::vector<Type*> verify_types_;
   // A list of interface types defined while parsing.

gcc/go/gofrontend/import.cc

@@ -41,6 +41,9 @@ go_add_search_path(const char* path)
 // When FILENAME is not an absolute path and does not start with ./ or
 // ../, we use the search path provided by -I and -L options.
 
+// When FILENAME does start with ./ or ../, we use
+// RELATIVE_IMPORT_PATH as a prefix.
+
 // When FILENAME does not exist, we try modifying FILENAME to find the
 // file.  We use the first of these which exists:
 //   * We append ".gox".
@@ -55,19 +58,35 @@ go_add_search_path(const char* path)
 // later in the search path.
 
 Import::Stream*
-Import::open_package(const std::string& filename, Location location)
+Import::open_package(const std::string& filename, Location location,
+		     const std::string& relative_import_path)
 {
   bool is_local;
   if (IS_ABSOLUTE_PATH(filename))
     is_local = true;
-  else if (filename[0] == '.' && IS_DIR_SEPARATOR(filename[1]))
+  else if (filename[0] == '.'
+	   && (filename[1] == '\0' || IS_DIR_SEPARATOR(filename[1])))
     is_local = true;
   else if (filename[0] == '.'
 	   && filename[1] == '.'
-	   && IS_DIR_SEPARATOR(filename[2]))
+	   && (filename[2] == '\0' || IS_DIR_SEPARATOR(filename[2])))
     is_local = true;
   else
     is_local = false;
+
+  std::string fn = filename;
+  if (is_local && !IS_ABSOLUTE_PATH(filename) && !relative_import_path.empty())
+    {
+      if (fn == ".")
+	{
+	  // A special case.
+	  fn = relative_import_path;
+	}
+      else
+	fn = relative_import_path + '/' + fn;
+      is_local = false;
+    }
+
   if (!is_local)
     {
       for (std::vector<std::string>::const_iterator p = search_path.begin();
@@ -77,14 +96,14 @@ Import::open_package(const std::string& filename, Location location)
 	  std::string indir = *p;
 	  if (!indir.empty() && indir[indir.size() - 1] != '/')
 	    indir += '/';
-	  indir += filename;
+	  indir += fn;
 	  Stream* s = Import::try_package_in_directory(indir, location);
 	  if (s != NULL)
 	    return s;
 	}
     }
 
-  Stream* s = Import::try_package_in_directory(filename, location);
+  Stream* s = Import::try_package_in_directory(fn, location);
   if (s != NULL)
     return s;
 

gcc/go/gofrontend/import.h

@@ -124,8 +124,10 @@ class Import
   // Find import data.  This searches the file system for FILENAME and
   // returns a pointer to a Stream object to read the data that it
   // exports.  LOCATION is the location of the import statement.
+  // RELATIVE_IMPORT_PATH is used as a prefix for a relative import.
   static Stream*
-  open_package(const std::string& filename, Location location);
+  open_package(const std::string& filename, Location location,
+	       const std::string& relative_import_path);
 
   // Constructor.
   Import(Stream*, Location);

gcc/go/lang.opt

@@ -61,6 +61,10 @@ fgo-prefix=
 Go Joined RejectNegative
 -fgo-prefix=<string>	Set package-specific prefix for exported Go names
 
+fgo-relative-import-path=
+Go Joined RejectNegative
+-fgo-relative-import-path=<path> Treat a relative import as relative to path
+
 frequire-return-statement
 Go Var(go_require_return_statement) Init(1) Warning
 Functions which return values must end with return statements