[PATCH] libio: handle opening a file when all files are closed (bug 31963)

[Sam James]

Andreas Schwab <schwab@suse.de> writes:

> _IO_list_all becomes NULL when all files (including standard files) are
> closed.

r-b for either patch (yours or H.J's)

> ---
>  libio/Makefile       |  1 +
>  libio/genops.c       |  3 ++-
>  libio/tst-closeall.c | 34 ++++++++++++++++++++++++++++++++++
>  3 files changed, 37 insertions(+), 1 deletion(-)
>  create mode 100644 libio/tst-closeall.c
>
> diff --git a/libio/Makefile b/libio/Makefile
> index 82c7e3ef0b..1f7031066c 100644
> --- a/libio/Makefile
> +++ b/libio/Makefile
> @@ -91,6 +91,7 @@ tests = \
>    tst-bz24051 \
>    tst-bz24153 \
>    tst-bz28828 \
> +  tst-closeall \
>    tst-eof \
>    tst-ext \
>    tst-ext2 \
> diff --git a/libio/genops.c b/libio/genops.c
> index 994ee9c0b1..99f5e80f20 100644
> --- a/libio/genops.c
> +++ b/libio/genops.c
> @@ -119,7 +119,8 @@ _IO_link_in (struct _IO_FILE_plus *fp)
>        if (_IO_vtable_offset ((FILE *) fp) == 0)
>  	{
>  	  fp->file._prevchain = (FILE **) &_IO_list_all;
> -	  _IO_list_all->file._prevchain = &fp->file._chain;
> +	  if (_IO_list_all != NULL)
> +	    _IO_list_all->file._prevchain = &fp->file._chain;
>  	}
>        _IO_list_all = fp;
>  #ifdef _IO_MTSAFE_IO
> diff --git a/libio/tst-closeall.c b/libio/tst-closeall.c
> new file mode 100644
> index 0000000000..34f5246490
> --- /dev/null
> +++ b/libio/tst-closeall.c
> @@ -0,0 +1,34 @@
> +/* Test that opening a file when all files are closed does not crash (bug 31963)
> +   Copyright (C) 2024 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <support/check.h>
> +#include <support/xstdio.h>
> +
> +static int
> +do_test (void)
> +{
> +  xfclose (stdin);
> +  xfclose (stdout);
> +  xfclose (stderr);
> +  FILE *f = xfopen ("/dev/null", "w");
> +  fprintf (f, "final\n");
> +  xfclose (f);
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
> -- 
> 2.45.2