[gcc r11-11033] libstdc++: Add utility for creating std::error_code from OS errors

[gcc r11-11033] libstdc++: Add utility for creating std::error_code from OS errors

[Jonathan Wakely]

https://gcc.gnu.org/g:e3af6b10673229c1a8cea7470e15fd9c09be6b6c

commit r11-11033-ge3af6b10673229c1a8cea7470e15fd9c09be6b6c
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Feb 10 18:00:00 2021 +0000

    libstdc++: Add utility for creating std::error_code from OS errors
    
    This adds a helper function to encapsulate obtaining an error code for
    errors from OS calls. For Windows we want to use GetLastError() and the
    system error category, but otherwise just use errno and the generic
    error category.
    
    This should not be used to replace existing uses of
    ec.assign(errno, generic_category()) because in those cases we really do
    want to get the value of errno, not a system-specific error. Only the
    cases that currently use GetLastError() are replace by this new
    function.
    
    Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
    
    libstdc++-v3/ChangeLog:
    
            * src/filesystem/ops-common.h (last_error): New helper function.
            (filesystem::do_space): Use last_error().
            * src/c++17/fs_ops.cc (fs::absolute, fs::create_hard_link)
            (fs::equivalent, fs::remove, fs::temp_directory_path): Use
            last_error().
            * src/filesystem/ops.cc (fs::create_hard_link)
            (fs::remove, fs::temp_directory_path): Likewise.
    
    (cherry picked from commit d71476c9df931f3ca674941f1942b03eabea010d)

Diff:
---
 libstdc++-v3/src/c++17/fs_ops.cc         | 10 +++++-----
 libstdc++-v3/src/filesystem/ops-common.h | 16 ++++++++++++++--
 libstdc++-v3/src/filesystem/ops.cc       |  4 ++--
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/libstdc++-v3/src/c++17/fs_ops.cc b/libstdc++-v3/src/c++17/fs_ops.cc
index 4155b4d64b9..4e2990d476d 100644
--- a/libstdc++-v3/src/c++17/fs_ops.cc
+++ b/libstdc++-v3/src/c++17/fs_ops.cc
@@ -117,7 +117,7 @@ fs::absolute(const path& p, error_code& ec)
   while (len > buf.size());
 
   if (len == 0)
-    ec.assign((int)GetLastError(), std::system_category());
+    ec = __last_system_error();
   else
     {
       buf.resize(len);
@@ -690,7 +690,7 @@ fs::create_hard_link(const path& to, const path& new_hard_link,
   if (CreateHardLinkW(new_hard_link.c_str(), to.c_str(), NULL))
     ec.clear();
   else
-    ec.assign((int)GetLastError(), system_category());
+    ec = __last_system_error();
 #else
   ec = std::make_error_code(std::errc::not_supported);
 #endif
@@ -882,12 +882,12 @@ fs::equivalent(const path& p1, const path& p2, error_code& ec) noexcept
       if (!h1 || !h2)
 	{
 	  if (!h1 && !h2)
-	    ec.assign((int)GetLastError(), system_category());
+	    ec = __last_system_error();
 	  return false;
 	}
       if (!h1.get_info() || !h2.get_info())
 	{
-	  ec.assign((int)GetLastError(), system_category());
+	  ec = __last_system_error();
 	  return false;
 	}
       return h1.info.dwVolumeSerialNumber == h2.info.dwVolumeSerialNumber
@@ -1263,7 +1263,7 @@ fs::remove(const path& p, error_code& ec) noexcept
 	  return true;
 	}
       else if (!ec)
-	ec.assign((int)GetLastError(), system_category());
+	ec = __last_system_error();
     }
   else if (status_known(st))
     ec.clear();
diff --git a/libstdc++-v3/src/filesystem/ops-common.h b/libstdc++-v3/src/filesystem/ops-common.h
index 54bafff2a9c..bf1017ea441 100644
--- a/libstdc++-v3/src/filesystem/ops-common.h
+++ b/libstdc++-v3/src/filesystem/ops-common.h
@@ -56,6 +56,18 @@
 namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+  // Get the last OS error (for POSIX this is just errno).
+  inline error_code
+  __last_system_error() noexcept
+  {
+#ifdef _GLIBCXX_FILESYSTEM_IS_WINDOWS
+    return {::GetLastError(), std::system_category()};
+#else
+    return {errno, std::generic_category()};
+#endif
+  }
+
 namespace filesystem
 {
 namespace __gnu_posix
@@ -557,7 +569,7 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM
 	ec.clear();
       }
     else
-      ec.assign((int)GetLastError(), std::system_category());
+      ec = std::last_system_error();
 #else
     ec = std::make_error_code(std::errc::not_supported);
 #endif
@@ -582,7 +594,7 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM
       } while (len > buf.size());
 
     if (len == 0)
-      ec.assign((int)GetLastError(), std::system_category());
+      ec = __last_system_error();
     else
       ec.clear();
 
diff --git a/libstdc++-v3/src/filesystem/ops.cc b/libstdc++-v3/src/filesystem/ops.cc
index b7df8d99b6c..6616d81cf77 100644
--- a/libstdc++-v3/src/filesystem/ops.cc
+++ b/libstdc++-v3/src/filesystem/ops.cc
@@ -598,7 +598,7 @@ fs::create_hard_link(const path& to, const path& new_hard_link,
   if (CreateHardLinkW(new_hard_link.c_str(), to.c_str(), NULL))
     ec.clear();
   else
-    ec.assign((int)GetLastError(), system_category());
+    ec = __last_system_error();
 #else
   ec = std::make_error_code(std::errc::not_supported);
 #endif
@@ -1070,7 +1070,7 @@ fs::remove(const path& p, error_code& ec) noexcept
 	  return true;
 	}
       else if (!ec)
-	ec.assign((int)GetLastError(), system_category());
+	ec = __last_system_error();
     }
   else if (status_known(st))
     ec.clear();