Check for overflow in filesystem::last_write_time

	* include/experimental/bits/fs_fwd.h (file_time_type): Simplify
	definition.
	* src/filesystem/ops.cc (file_time): Take error_code parameter and
	check for overflow.
	(do_copy_file, last_write_time): Pass error_code in file_time calls.
	* testsuite/experimental/filesystem/operations/last_write_time.cc:
	New.
	* testsuite/util/testsuite_fs.h (scoped_file): Define RAII helper.

From-SVN: r240587

1 files changed, 19 insertions, 11 deletions

diff --git a/libstdc++-v3/src/filesystem/ops.cc b/libstdc++-v3/src/filesystem/ops.cc
index 0ecb8b9..659cfbb 100644
--- a/libstdc++-v3/src/filesystem/ops.cc
+++ b/libstdc++-v3/src/filesystem/ops.cc
@@ -288,16 +288,24 @@ namespace
   }
 
   inline fs::file_time_type
-  file_time(const stat_type& st) noexcept
+  file_time(const stat_type& st, std::error_code& ec) noexcept
   {
     using namespace std::chrono;
-    return fs::file_time_type{
 #ifdef _GLIBCXX_USE_ST_MTIM
-	seconds{st.st_mtim.tv_sec} + nanoseconds{st.st_mtim.tv_nsec}
+    time_t s = st.st_mtim.tv_sec;
+    nanoseconds ns{st.st_mtim.tv_nsec};
 #else
-	seconds{st.st_mtime}
+    time_t s = st.st_mtime;
+    nanoseconds ns{};
 #endif
-    };
+
+    if (s >= (nanoseconds::max().count() / 1e9))
+      {
+	ec = std::make_error_code(std::errc::value_too_large); // EOVERFLOW
+	return fs::file_time_type::min();
+      }
+    ec.clear();
+    return fs::file_time_type{seconds{s} + ns};
   }
 
   // Returns true if the file descriptor was successfully closed,
@@ -373,11 +381,11 @@ namespace
 	  }
 	else if (is_set(option, opts::update_existing))
 	  {
-	    if (file_time(*from_st) <= file_time(*to_st))
-	      {
-		ec.clear();
-		return false;
-	      }
+	    const auto from_mtime = file_time(*from_st, ec);
+	    if (ec)
+	      return false;
+	    if ((from_mtime <= file_time(*to_st, ec)) || ec)
+	      return false;
 	  }
 	else if (!is_set(option, opts::overwrite_existing))
 	  {
@@ -1036,7 +1044,7 @@ fs::last_write_time(const path& p)
 fs::file_time_type
 fs::last_write_time(const path& p, error_code& ec) noexcept
 {
-  return do_stat(p, ec, [](const auto& st) { return file_time(st); },
+  return do_stat(p, ec, [&ec](const auto& st) { return file_time(st, ec); },
 		 file_time_type::min());
 }