Address LWG 2849 and fix missing failure condition in copy_file.

Previously copy_file didn't handle the case where the input and
output were the same file.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@324187 91177308-0d34-0410-b5e6-96231b3b80d8

src/experimental/filesystem/operations.cpp

@@ -263,10 +263,13 @@ void __copy(const path& from, const path& to, copy_options options,
 bool __copy_file(const path& from, const path& to, copy_options options,
                  std::error_code *ec)
 {
-    if (ec) ec->clear();
+    using StatT = struct ::stat;
+    if (ec)
+      ec->clear();
 
     std::error_code m_ec;
-    auto from_st = detail::posix_stat(from, &m_ec);
+    StatT from_stat;
+    auto from_st = detail::posix_stat(from, from_stat, &m_ec);
     if (not is_regular_file(from_st)) {
       if (not m_ec)
         m_ec = make_error_code(errc::not_supported);
@@ -274,7 +277,8 @@ bool __copy_file(const path& from, const path& to, copy_options options,
       return false;
     }
 
-    auto to_st = detail::posix_stat(to, &m_ec);
+    StatT to_stat;
+    auto to_st = detail::posix_stat(to, to_stat, &m_ec);
     if (!status_known(to_st)) {
         set_or_throw(m_ec, ec, "copy_file", from, to);
         return false;
@@ -285,6 +289,11 @@ bool __copy_file(const path& from, const path& to, copy_options options,
         set_or_throw(make_error_code(errc::not_supported), ec, "copy_file", from, to);
         return false;
     }
+    if (to_exists && detail::stat_equivalent(from_stat, to_stat)) {
+      set_or_throw(make_error_code(errc::file_exists), ec, "copy_file", from,
+                   to);
+      return false;
+    }
     if (to_exists && bool(copy_options::skip_existing & options)) {
         return false;
     }
@@ -302,7 +311,8 @@ bool __copy_file(const path& from, const path& to, copy_options options,
         return detail::copy_file_impl(from, to, from_st.permissions(), ec);
     }
     else {
-        set_or_throw(make_error_code(errc::file_exists), ec, "copy", from, to);
+      set_or_throw(make_error_code(errc::file_exists), ec, "copy_file", from,
+                   to);
       return false;
     }
 
@@ -443,7 +453,7 @@ bool __equivalent(const path& p1, const path& p2, std::error_code *ec)
     if (!exists(s2))
       return make_unsupported_error();
     if (ec) ec->clear();
-    return (st1.st_dev == st2.st_dev && st1.st_ino == st2.st_ino);
+    return detail::stat_equivalent(st1, st2);
 }
 
 

test/std/experimental/filesystem/fs.op.funcs/fs.op.copy_file/copy_file.pass.cpp

@@ -70,17 +70,21 @@ TEST_CASE(test_error_reporting)
     scoped_test_env env;
     const path file = env.create_file("file1", 42);
     const path file2 = env.create_file("file2", 55);
+    const path non_regular_file = env.create_fifo("non_reg");
     const path dne = env.make_env_path("dne");
     { // exists(to) && equivalent(to, from)
         std::error_code ec;
-        TEST_CHECK(fs::copy_file(file, file, ec) == false);
+        TEST_CHECK(fs::copy_file(file, file, copy_options::overwrite_existing,
+                                 ec) == false);
         TEST_REQUIRE(ec);
+        TEST_CHECK(ec == std::make_error_code(std::errc::file_exists));
         TEST_CHECK(checkThrow(file, file, ec));
     }
     { // exists(to) && !(skip_existing | overwrite_existing | update_existing)
         std::error_code ec;
         TEST_CHECK(fs::copy_file(file, file2, ec) == false);
         TEST_REQUIRE(ec);
+        TEST_CHECK(ec == std::make_error_code(std::errc::file_exists));
         TEST_CHECK(checkThrow(file, file2, ec));
     }
 }
@@ -181,6 +185,7 @@ TEST_CASE(non_regular_file_test)
         TEST_REQUIRE(fs::copy_file(file, fifo, copy_options::overwrite_existing, ec) == false);
         TEST_CHECK(ec);
         TEST_CHECK(ec != GetTestEC());
+        TEST_CHECK(ec == std::make_error_code(std::errc::not_supported));
         TEST_CHECK(is_fifo(fifo));
     }
 }

www/upcoming_meeting.html

@@ -63,7 +63,7 @@
 <tr><td><a href="https://wg21.link/LWG2243">2243</a></td><td><tt>istream::putback</tt> problem</td><td>Jacksonville</td><td>Complete</td></tr>
 <tr><td><a href="https://wg21.link/LWG2816">2816</a></td><td><tt>resize_file</tt> has impossible postcondition</td><td>Jacksonville</td><td><i>Nothing to do</i></td></tr>
 <tr><td><a href="https://wg21.link/LWG2843">2843</a></td><td>Unclear behavior of <tt>std::pmr::memory_resource::do_allocate()</tt></td><td>Jacksonville</td><td></td></tr>
-<tr><td><a href="https://wg21.link/LWG2849">2849</a></td><td>Why does <tt>!is_regular_file(from)</tt> cause <tt>copy_file</tt> to report a "file already exists" error?</td><td>Jacksonville</td><td></td></tr>
+<tr><td><a href="https://wg21.link/LWG2849">2849</a></td><td>Why does <tt>!is_regular_file(from)</tt> cause <tt>copy_file</tt> to report a "file already exists" error?</td><td>Jacksonville</td><td>Nothing to do</td></tr>
 <tr><td><a href="https://wg21.link/LWG2851">2851</a></td><td><tt>std::filesystem</tt> enum classes are now underspecified</td><td>Jacksonville</td><td></td></tr>
 <tr><td><a href="https://wg21.link/LWG2969">2969</a></td><td><tt>polymorphic_allocator::construct()</tt> shouldn't pass <tt>resource()</tt></td><td>Jacksonville</td><td></td></tr>
 <tr><td><a href="https://wg21.link/LWG2975">2975</a></td><td>Missing case for <tt>pair</tt> construction in scoped and polymorphic allocators</td><td>Jacksonville</td><td></td></tr>
@@ -100,7 +100,7 @@
 <li> 2243 - We already do this.</li>
 <li> 2816 - Wording changes only</li>
 <li> 2843 - We don't have PMRs yet</li>
-<li> 2849 - Eric? </li>
+<li> 2849 - We already report different errors. </li>
 <li> 2851 - Eric? </li>
 <li> 2969 - We don't have PMRs yet</li>
 <li> 2975 - We can do the scoped_ bit, but the PMR stuff will have to wait.</li>