From e3af6b10673229c1a8cea7470e15fd9c09be6b6c Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Wed, 10 Feb 2021 18:00:00 +0000
Subject: [PATCH] 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)
---
 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 4155b4d64b9c..4e2990d476d3 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 54bafff2a9cf..bf1017ea4418 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 b7df8d99b6cf..6616d81cf776 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();
-- 
2.47.2