[PATCH v3 0/3] compat/mingw: implement POSIX-style atomic renames

Hi,

this is third version of my patch series that introduces POSIX-style atomic renames on Windows to fix concurrent writes with the reftable backend.

Changes compared to v2:

  - Use `DWORD` instead of `int` to store the `access` flags.

  - Fix handling of `oflags`.

  - Add a comment referring to `mingw_open_append()` for why convert
    `ERROR_INVALID_PARAMETER` to `ERROR_PATH_NOT_FOUND`.

Thanks!

Patrick

Patrick Steinhardt (3):
  compat/mingw: share file handles created via `CreateFileW()`
  compat/mingw: allow deletion of most opened files
  compat/mingw: support POSIX semantics for atomic renames

 compat/mingw.c             | 157 +++++++++++++++++++++++++++++++++++--
 t/t0610-reftable-basics.sh |   8 +-
 2 files changed, 156 insertions(+), 9 deletions(-)

Range-diff against v2:
1:  63c2cfa87a4 = 1:  63c2cfa87a4 compat/mingw: share file handles created via `CreateFileW()`
2:  c308eafbbb5 ! 2:  91d434116f3 compat/mingw: allow deletion of most opened files
    @@ compat/mingw.c: static int mingw_open_append(wchar_t const *wfilename, int oflag
     +		.bInheritHandle = !(oflags & O_NOINHERIT),
     +	};
     +	HANDLE handle;
    -+	int access;
    ++	DWORD access;
     +	int fd;
     +
     +	/* We only support basic flags. */
    @@ compat/mingw.c: static int mingw_open_append(wchar_t const *wfilename, int oflag
     +		return -1;
     +	}
     +
    -+	if (oflags & O_RDWR)
    ++	switch (oflags & O_ACCMODE) {
    ++	case O_RDWR:
     +		access = GENERIC_READ | GENERIC_WRITE;
    -+	else if (oflags & O_WRONLY)
    ++		break;
    ++	case O_WRONLY:
     +		access = GENERIC_WRITE;
    -+	else
    ++		break;
    ++	default:
     +		access = GENERIC_READ;
    ++		break;
    ++	}
     +
     +	handle = CreateFileW(filename, access,
     +			     FILE_SHARE_WRITE | FILE_SHARE_READ | FILE_SHARE_DELETE,
     +			     &security_attributes, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
     +	if (handle == INVALID_HANDLE_VALUE) {
     +		DWORD err = GetLastError();
    ++
    ++		/* See `mingw_open_append()` for why we have this conversion. */
     +		if (err == ERROR_INVALID_PARAMETER)
     +			err = ERROR_PATH_NOT_FOUND;
    ++
     +		errno = err_win_to_posix(err);
     +		return -1;
     +	}
3:  ee1e92e593e = 3:  2447d332a85 compat/mingw: support POSIX semantics for atomic renames