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From: "m.heinzler at heinzler dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/98985] New: libstdc++: filesystem::rename not
 overwriting files on Windows
Date: Sun, 07 Feb 2021 16:58:30 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98985

            Bug ID: 98985
           Summary: libstdc++: filesystem::rename not overwriting files on
                    Windows
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: m.heinzler at heinzler dot de
  Target Milestone: ---

Created attachment 50139
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D50139&action=3Dedit
Proposed fix

filesystem::rename must replace existing files and currently does so on most
platforms by simply calling posix::rename. But on Windows (specifically Min=
GW),
posix::rename refers to Microsoft's MSVCRT which does not overwrite files.
See:
https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/rename-wre=
name?view=3Dmsvc-160

I attached a patch that falls back to the WinAPI in this case and tested it
successfully. This is also how Microsoft implements filesystem::rename.

As I'm not familiar with the codebase I wasn't able to add a simple test ca=
se
for this. If someone could give me a hint which files to touch I could also
work on that.=