libstdc++: Fix error handling in filesystem::remove_all (PR93201)

When recursing into a directory, any errors that occur while removing a
directory entry are ignored, because the subsequent increment of the
directory iterator clears the error_code object.

This fixes that bug by checking the result of each recursive operation
before incrementing. This is a change in observable behaviour, because
previously other directory entries would still be removed even if one
(or more) couldn't be removed due to errors. Now the operation stops on
the first error, which is what the code intended to do all along. The
standard doesn't specify what happens in this case (because the order
that the entries are processed is unspecified anyway).

It also improves the error reporting so that the name of the file that
could not be removed is included in the filesystem_error exception. This
is done by introducing a new helper type for reporting errors with
additional context and a new function that uses that type. Then the
overload of std::filesystem::remove_all that throws an exception can use
the new function to ensure any exception contains the additional
information.

For std::experimental::filesystem::remove_all just fix the bug where
errors are ignored.

	PR libstdc++/93201
	* src/c++17/fs_ops.cc (do_remove_all): New function implementing more
	detailed error reporting for remove_all. Check result of recursive
	call before incrementing iterator.
	(remove_all(const path&), remove_all(const path&, error_code&)): Use
	do_remove_all.
	* src/filesystem/ops.cc (remove_all(const path&, error_code&)): Check
	result of recursive call before incrementing iterator.
	* testsuite/27_io/filesystem/operations/remove_all.cc: Check errors
	are reported correctly.
	* testsuite/experimental/filesystem/operations/remove_all.cc: Likewise.

From-SVN: r280014

5 files changed, 182 insertions, 32 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 98449aa..4597598 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,17 @@
+2020-01-08  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/93201
+	* src/c++17/fs_ops.cc (do_remove_all): New function implementing more
+	detailed error reporting for remove_all. Check result of recursive
+	call before incrementing iterator.
+	(remove_all(const path&), remove_all(const path&, error_code&)): Use
+	do_remove_all.
+	* src/filesystem/ops.cc (remove_all(const path&, error_code&)): Check
+	result of recursive call before incrementing iterator.
+	* testsuite/27_io/filesystem/operations/remove_all.cc: Check errors
+	are reported correctly.
+	* testsuite/experimental/filesystem/operations/remove_all.cc: Likewise.
+
 2020-01-07  Thomas Rodgers  <trodgers@redhat.com>
 
 	* include/std/condition_variable
diff --git a/libstdc++-v3/src/c++17/fs_ops.cc b/libstdc++-v3/src/c++17/fs_ops.cc
index 8ad2e7f..873f93a 100644
--- a/libstdc++-v3/src/c++17/fs_ops.cc
+++ b/libstdc++-v3/src/c++17/fs_ops.cc
@@ -1275,42 +1275,105 @@ fs::remove(const path& p, error_code& ec) noexcept
   return false;
 }
 
+namespace std::filesystem
+{
+namespace
+{
+  struct ErrorReporter
+  {
+    explicit
+    ErrorReporter(error_code& ec) : code(&ec)
+    { }
+
+    explicit
+    ErrorReporter(const char* s, const path& p)
+    : code(nullptr), msg(s), path1(&p)
+    { }
+
+    error_code* code;
+    const char* msg;
+    const path* path1;
+
+    void
+    report(const error_code& ec) const
+    {
+      if (code)
+	*code = ec;
+      else
+	_GLIBCXX_THROW_OR_ABORT(filesystem_error(msg, *path1, ec));
+    }
+
+    void
+    report(const error_code& ec, const path& path2) const
+    {
+      if (code)
+	*code = ec;
+      else if (path2 != *path1)
+	_GLIBCXX_THROW_OR_ABORT(filesystem_error(msg, *path1, path2, ec));
+      else
+	_GLIBCXX_THROW_OR_ABORT(filesystem_error(msg, *path1, ec));
+    }
+  };
+
+  uintmax_t
+  do_remove_all(const path& p, const ErrorReporter& err)
+  {
+    error_code ec;
+    const auto s = symlink_status(p, ec);
+    if (!status_known(s))
+      {
+	if (ec)
+	  err.report(ec, p);
+	return -1;
+      }
+
+    ec.clear();
+    if (s.type() == file_type::not_found)
+      return 0;
+
+    uintmax_t count = 0;
+    if (s.type() == file_type::directory)
+      {
+	directory_iterator d(p, ec), end;
+	while (d != end)
+	  {
+	    const auto removed = fs::do_remove_all(d->path(), err);
+	    if (removed == numeric_limits<uintmax_t>::max())
+	      return -1;
+	    count += removed;
+
+	    d.increment(ec);
+	    if (ec)
+	      {
+		err.report(ec, p);
+		return -1;
+	      }
+	  }
+      }
+
+    if (fs::remove(p, ec))
+      ++count;
+    if (ec)
+      {
+	err.report(ec, p);
+	return -1;
+      }
+    return count;
+  }
+}
+}
 
 std::uintmax_t
 fs::remove_all(const path& p)
 {
-  error_code ec;
-  const auto result = remove_all(p, ec);
-  if (ec)
-    _GLIBCXX_THROW_OR_ABORT(filesystem_error("cannot remove all", p, ec));
-  return result;
+  return fs::do_remove_all(p, ErrorReporter{"cannot remove all", p});
 }
 
 std::uintmax_t
 fs::remove_all(const path& p, error_code& ec)
 {
-  const auto s = symlink_status(p, ec);
-  if (!status_known(s))
-    return -1;
-
   ec.clear();
-  if (s.type() == file_type::not_found)
-    return 0;
-
-  uintmax_t count = 0;
-  if (s.type() == file_type::directory)
-    {
-      for (directory_iterator d(p, ec), end; !ec && d != end; d.increment(ec))
-	count += fs::remove_all(d->path(), ec);
-      if (ec.value() == ENOENT)
-	ec.clear();
-      else if (ec)
-	return -1;
-    }
-
-  if (fs::remove(p, ec))
-    ++count;
-  return ec ? -1 : count;
+  return fs::do_remove_all(p, ErrorReporter{ec});
 }
 
 void
diff --git a/libstdc++-v3/src/filesystem/ops.cc b/libstdc++-v3/src/filesystem/ops.cc
index 79dc0fc..29ea9c0 100644
--- a/libstdc++-v3/src/filesystem/ops.cc
+++ b/libstdc++-v3/src/filesystem/ops.cc
@@ -1099,12 +1099,17 @@ fs::remove_all(const path& p, error_code& ec) noexcept
   uintmax_t count = 0;
   if (s.type() == file_type::directory)
     {
-      for (directory_iterator d(p, ec), end; !ec && d != end; d.increment(ec))
-	count += fs::remove_all(d->path(), ec);
-      if (ec.value() == ENOENT)
-	ec.clear();
-      else if (ec)
-	return -1;
+      directory_iterator d(p, ec), end;
+      while (!ec && d != end)
+	{
+	  const auto removed = fs::remove_all(d->path(), ec);
+	  if (removed == numeric_limits<uintmax_t>::max())
+	    return -1;
+	  count += removed;
+	  d.increment(ec);
+	  if (ec)
+	    return -1;
+	}
     }
 
   if (fs::remove(p, ec))
diff --git a/libstdc++-v3/testsuite/27_io/filesystem/operations/remove_all.cc b/libstdc++-v3/testsuite/27_io/filesystem/operations/remove_all.cc
index 5b920e4..7e018b5 100644
--- a/libstdc++-v3/testsuite/27_io/filesystem/operations/remove_all.cc
+++ b/libstdc++-v3/testsuite/27_io/filesystem/operations/remove_all.cc
@@ -140,10 +140,45 @@ test03()
   VERIFY( !exists(p) );
 }
 
+void
+test04()
+{
+#if defined(__MINGW32__) || defined(__MINGW64__)
+  // no permissions
+#else
+  // PR libstdc++/93201
+  std::error_code ec;
+  std::uintmax_t n;
+
+  auto dir = __gnu_test::nonexistent_path();
+  fs::create_directory(dir);
+  __gnu_test::scoped_file f(dir/"file");
+  // remove write permission on the directory:
+  fs::permissions(dir, fs::perms::owner_read|fs::perms::owner_exec);
+  n = fs::remove_all(dir, ec);
+  VERIFY( n == -1 );
+  VERIFY( ec == std::errc::permission_denied ); // not ENOTEMPTY
+
+  try {
+    fs::remove_all(dir);
+    VERIFY( false );
+  } catch (const fs::filesystem_error& e) {
+    VERIFY( e.code() == std::errc::permission_denied );
+    // First path is the argument to remove_all
+    VERIFY( e.path1() == dir );
+    // Second path is the first file that couldn't be removed
+    VERIFY( e.path2() == dir/"file" );
+  }
+
+  fs::permissions(dir, fs::perms::owner_write, fs::perm_options::add);
+#endif
+}
+
 int
 main()
 {
   test01();
   test02();
   test03();
+  test04();
 }
diff --git a/libstdc++-v3/testsuite/experimental/filesystem/operations/remove_all.cc b/libstdc++-v3/testsuite/experimental/filesystem/operations/remove_all.cc
index 9e46c76..0e2aeda 100644
--- a/libstdc++-v3/testsuite/experimental/filesystem/operations/remove_all.cc
+++ b/libstdc++-v3/testsuite/experimental/filesystem/operations/remove_all.cc
@@ -108,9 +108,42 @@ test02()
   VERIFY( !exists(dir) );
 }
 
+void
+test04()
+{
+#if defined(__MINGW32__) || defined(__MINGW64__)
+  // no permissions
+#else
+  // PR libstdc++/93201
+  std::error_code ec;
+  std::uintmax_t n;
+
+  auto dir = __gnu_test::nonexistent_path();
+  fs::create_directory(dir);
+  __gnu_test::scoped_file f(dir/"file");
+  // remove write permission on the directory:
+  fs::permissions(dir, fs::perms::owner_read|fs::perms::owner_exec);
+  n = fs::remove_all(dir, ec);
+  VERIFY( n == -1 );
+  VERIFY( ec == std::errc::permission_denied ); // not ENOTEMPTY
+
+  try {
+    fs::remove_all(dir);
+    VERIFY( false );
+  } catch (const fs::filesystem_error& e) {
+    VERIFY( e.code() == std::errc::permission_denied );
+    // First path is the argument to remove_all
+    VERIFY( e.path1() == dir );
+  }
+
+  fs::permissions(dir, fs::perms::owner_write|fs::perms::add_perms);
+#endif
+}
+
 int
 main()
 {
   test01();
   test02();
+  test04();
 }