LWG2725 Fix error reporting for filesystem::exists

	* include/experimental/bits/fs_ops.h
	(exists(const path&, error_code&)): Clear error if status is known
	(LWG 2725).
	(status(const path&, error_code&)): Handle EOVERFLOW.
	* testsuite/experimental/filesystem/operations/exists.cc: Test
	overload taking an error_code.

From-SVN: r241417

libstdc++-v3/ChangeLog

 2016-10-21  Jonathan Wakely  <jwakely@redhat.com>
 
+	* include/experimental/bits/fs_ops.h
+	(exists(const path&, error_code&)): Clear error if status is known
+	(LWG 2725).
+	(status(const path&, error_code&)): Handle EOVERFLOW.
+	* testsuite/experimental/filesystem/operations/exists.cc: Test
+	overload taking an error_code.
+
 	* include/experimental/bits/fs_path.h (path::path(string_type&&))
 	(path::operator=(string&&), path::assign(string_type&&)): Define
 	construction and assignment from string_type rvalues (LWG 2707).

libstdc++-v3/include/experimental/bits/fs_ops.h

@@ -112,6 +112,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   void current_path(const path& __p);
   void current_path(const path& __p, error_code& __ec) noexcept;
 
+  bool
+  equivalent(const path& __p1, const path& __p2);
+
+  bool
+  equivalent(const path& __p1, const path& __p2, error_code& __ec) noexcept;
+
   inline bool
   exists(file_status __s) noexcept
   { return status_known(__s) && __s.type() != file_type::not_found; }
@@ -122,13 +128,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   inline bool
   exists(const path& __p, error_code& __ec) noexcept
-  { return exists(status(__p, __ec)); }
-
-  bool
-  equivalent(const path& __p1, const path& __p2);
-
-  bool
-  equivalent(const path& __p1, const path& __p2, error_code& __ec) noexcept;
+  {
+    auto __s = status(__p, __ec);
+    if (status_known(__s))
+      __ec.clear();
+    return exists(__s);
+  }
 
   uintmax_t file_size(const path& __p);
   uintmax_t file_size(const path& __p, error_code& __ec) noexcept;

libstdc++-v3/src/filesystem/ops.cc

@@ -1297,7 +1297,7 @@ fs::space(const path& p, error_code& ec) noexcept
 
 #ifdef _GLIBCXX_HAVE_SYS_STAT_H
 fs::file_status
-fs::status(const fs::path& p, std::error_code& ec) noexcept
+fs::status(const fs::path& p, error_code& ec) noexcept
 {
   file_status status;
   stat_type st;
@@ -1307,6 +1307,10 @@ fs::status(const fs::path& p, std::error_code& ec) noexcept
       ec.assign(err, std::generic_category());
       if (is_not_found_errno(err))
 	status.type(file_type::not_found);
+#ifdef EOVERFLOW
+      else if (err == EOVERFLOW)
+	status.type(file_type::unknown);
+#endif
     }
   else
     {

libstdc++-v3/testsuite/experimental/filesystem/operations/exists.cc

@@ -33,6 +33,18 @@ test01()
   VERIFY( exists(path{"."}) );
   VERIFY( exists(path{".."}) );
   VERIFY( exists(std::experimental::filesystem::current_path()) );
+
+  std::error_code ec = std::make_error_code(std::errc::invalid_argument);
+  VERIFY( exists(path{"/"}, ec) );
+  VERIFY( !ec );
+  VERIFY( exists(path{"/."}, ec) );
+  VERIFY( !ec );
+  VERIFY( exists(path{"."}, ec) );
+  VERIFY( !ec );
+  VERIFY( exists(path{".."}, ec) );
+  VERIFY( !ec );
+  VERIFY( exists(std::experimental::filesystem::current_path(), ec) );
+  VERIFY( !ec );
 }
 
 void
@@ -40,6 +52,10 @@ test02()
 {
   path rel = __gnu_test::nonexistent_path();
   VERIFY( !exists(rel) );
+
+  std::error_code ec = std::make_error_code(std::errc::invalid_argument);
+  VERIFY( !exists(rel, ec) );
+  VERIFY( !ec ); // DR 2725
 }
 
 void
@@ -47,6 +63,38 @@ test03()
 {
   path abs = absolute(__gnu_test::nonexistent_path());
   VERIFY( !exists(abs) );
+
+  std::error_code ec = std::make_error_code(std::errc::invalid_argument);
+  VERIFY( !exists(abs, ec) );
+  VERIFY( !ec ); // DR 2725
+}
+
+void
+test04()
+{
+  using perms = std::experimental::filesystem::perms;
+  path p = __gnu_test::nonexistent_path();
+  create_directory(p);
+  permissions(p, perms::all | perms::remove_perms);
+
+  auto unr = p / "unreachable";
+  std::error_code ec;
+  VERIFY( !exists(unr, ec) );
+  VERIFY( ec == std::errc::permission_denied );
+  ec.clear();
+  try
+  {
+    exists(unr);
+  }
+  catch(const std::experimental::filesystem::filesystem_error& ex)
+  {
+    ec = ex.code();
+    VERIFY( ex.path1() == unr );
+  }
+  VERIFY( ec == std::errc::permission_denied );
+
+  permissions(p, perms::owner_all);
+  remove(p);
 }
 
 int
@@ -55,4 +103,5 @@ main()
   test01();
   test02();
   test03();
+  test04();
 }