New subject: [Bug 57008] _fdopen(0) does not return stdin after it was closed

28 Jul 2024


      https://bugs.winehq.org/show_bug.cgi?id=57008
Bug ID: 57008
           Summary: _fdopen(0) does not return stdin after it was closed
           Product: Wine
           Version: unspecified
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: msvcrt
          Assignee: wine-bugs@winehq.org
          Reporter: pipcet@protonmail.com
      Distribution: ---
GNU Emacs contains the following code (abbreviated slightly):
HANDLE stdin_save =  INVALID_HANDLE_VALUE;
    DuplicateHandle (parent,
             GetStdHandle (STD_INPUT_HANDLE),
             parent,
             &stdin_save,
             0,
             FALSE,
             DUPLICATE_SAME_ACCESS);
    fclose (stdin);
    if (stdin_save != INVALID_HANDLE_VALUE)
      _open_osfhandle ((intptr_t) stdin_save, O_TEXT);
    else
      _open ("nul", O_TEXT | O_NOINHERIT | O_RDONLY);
    _fdopen (0, "r");
The idea is that the last call to _fdopen will return stdin, so we can continue
using stdin after this code runs, but its HANDLE will have become
non-inheritable.
This doesn't work on wine, which allocates a new FILE * in msvcrt_alloc_fp:
for (i = 3; i < MSVCRT_max_streams; i++)
  {
    file = msvcrt_get_file(i);
    if (!file)
      return NULL;
if (file->_flag == 0)
    {
      ...
      return file;
    }
  }
The loop starts at index 3, not 0, so the stdin/stdout/stderr handles are never
reused.
Of course, what Emacs does is highly dodgy and not documented to work;
apparently, it doesn't work with UCRT on native Windows either. However, there
is interest in keeping Emacs usable on very old Windows systems, so it's
possible that changing the Emacs code would break things subtly.
Is there any possibility or interest in changing wine so it emulates MSVCRT
behavior for this application? Changing "i = 3" to "i = 0" would probably
suffice...
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[Bug 57008] New: _fdopen(0) does not return stdin after it was closed