Fix concatenation bug in filesystem::path

When erasing a trailing empty filename component, the output iterator
was not decremented, causing the next component to be created at the
wrong position.

	* src/filesystem/std-path.cc (path::operator+=(const path&)): Fix
	incorrect treatment of empty filename after trailing slash.
	* testsuite/27_io/filesystem/path/concat/path.cc: Test problem case.

From-SVN: r267574

1 files changed, 9 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/27_io/filesystem/path/concat/path.cc b/libstdc++-v3/testsuite/27_io/filesystem/path/concat/path.cc
index b653219a7f7..e2a14bd8fcc 100644
--- a/libstdc++-v3/testsuite/27_io/filesystem/path/concat/path.cc
+++ b/libstdc++-v3/testsuite/27_io/filesystem/path/concat/path.cc
@@ -59,9 +59,18 @@ test02()
   }
 }
 
+void
+test03()
+{
+  path p = "a/";
+  p += path("/b");
+  compare_paths(p, "a//b");
+}
+
 int
 main()
 {
   test01();
   test02();
+  test03();
 }