[PATCH] Add a new fwrite test for read-only streams

[Adhemerval Zanella Netto]

On 29/08/24 11:59, Tulio Magno Quites Machado Filho wrote:
> From: Tulio Magno Quites Machado Filho <tuliom@redhat.com>
> 
> Ensure that fwrite() behaves correctly even when the stream is
> read-only.

The patch fails to apply, as indicated by CI, but it seems to due
new tests added on stdio-common/Makefile.

> ---
>  stdio-common/Makefile        |  1 +
>  stdio-common/tst-fwrite-ro.c | 56 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 57 insertions(+)
>  create mode 100644 stdio-common/tst-fwrite-ro.c
> 
> diff --git a/stdio-common/Makefile b/stdio-common/Makefile
> index e4f0146d2c7..315152f30df 100644
> --- a/stdio-common/Makefile
> +++ b/stdio-common/Makefile
> @@ -218,6 +218,7 @@ tests := \
>    tst-fphex-wide \
>    tst-fseek \
>    tst-fwrite \
> +  tst-fwrite-ro \
>    tst-gets \
>    tst-grouping \
>    tst-grouping2 \
> diff --git a/stdio-common/tst-fwrite-ro.c b/stdio-common/tst-fwrite-ro.c
> new file mode 100644
> index 00000000000..cd67bf774ee
> --- /dev/null
> +++ b/stdio-common/tst-fwrite-ro.c
> @@ -0,0 +1,56 @@
> +/* Test fwrite on a read-only stream.
> +   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 <stdio.h>
> +#include <support/check.h>
> +#include <support/temp_file.h>
> +#include <support/xstdio.h>
> +#include <support/xunistd.h>
> +
> +static int
> +do_test (void)
> +{
> +  int fd;
> +  FILE *f;
> +
> +  /* Create a temporary file and open it in read-only mode.  */
> +  TEST_VERIFY_EXIT ((fd = create_temp_file ("tst-fwrite-ro", NULL)));

No implicit checks and this would fail if create_temp_file fails with -1.

> +  TEST_VERIFY_EXIT ((f = fdopen (fd, "r")));
No implicit checks.


> +
> +  /* Try to write to the temporary file with nmemb = 0, then check that
> +     fwrite returns 0.  No errors are expected from this.  */
> +  TEST_COMPARE (fwrite ("a", 1, 0, f), 0);
> +  TEST_COMPARE (ferror (f), 0);
> +
> +  /* Try to write to the temporary file with size = 0, then check that
> +     fwrite returns 0.  No errors are expected from this.  */
> +  TEST_COMPARE (fwrite ("a", 0, 1, f), 0);
> +  TEST_COMPARE (ferror (f), 0);
> +
> +  /* Try to write a single byte to the temporary file, then check that
> +     fwrite returns 0.  Check if an error was reported.  */
> +  TEST_COMPARE (fwrite ("a", 1, 1, f), 0);
> +  TEST_COMPARE (ferror (f), 1);

I think you also check check that the file is actually empty.

> +
> +  clearerr (f);
> +  xfclose (f);
> +
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>