[PATCH v2] Test that errno is set to 0 at program startup

[Carlos O'Donell]

On 9/19/24 11:11 AM, Aaron Merey wrote:
> Add new testcase elf/tst-startup-errno.c which tests that errno is set
> to 0 at first ELF constructor execution and at the start of the
> program's main function.

LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> 
> Tested for x86_64
> ---
> v1:
> https://sourceware.org/pipermail/libc-alpha/2024-September/159857.html
> 
> v2 changes:
> Testcase calls main() directly and no longer includes test-driver.c.
> 
>  elf/Makefile            |  1 +
>  elf/tst-startup-errno.c | 58 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 59 insertions(+)
>  create mode 100644 elf/tst-startup-errno.c
> 
> diff --git a/elf/Makefile b/elf/Makefile
> index 00622ace9d..be1a99ea26 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -457,6 +457,7 @@ tests += \
>    tst-single_threaded-pthread \
>    tst-sonamemove-dlopen \
>    tst-sonamemove-link \
> +  tst-startup-errno \

OK. Bare test.

>    tst-thrlock \
>    tst-tls-dlinfo \
>    tst-tls-ie \
> diff --git a/elf/tst-startup-errno.c b/elf/tst-startup-errno.c
> new file mode 100644
> index 0000000000..59a1005fb6
> --- /dev/null
> +++ b/elf/tst-startup-errno.c
> @@ -0,0 +1,58 @@
> +/* Test the value of errno at program startup.

OK.

> +   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 <errno.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +
> +/* Verify that errno is 0 at first ELF constructor execution and at
> +   the start of main.  */
> +
> +static void set_ctor_errno (void) __attribute__((constructor));
> +static int ctor_errno = -1;
> +
> +static void
> +set_ctor_errno (void)
> +{
> +  ctor_errno = errno;
> +}
> +
> +static int
> +get_ctor_errno (void)
> +{
> +  return ctor_errno;
> +}
> +
> +int
> +main (void)
> +{
> +  if (errno != 0)
> +    {
> +      printf ("At start of main errno set to %d != 0\n", errno);
> +      exit (1);

OK. Fails the test.

> +    }
> +
> +  if (get_ctor_errno () != 0)
> +    {
> +      printf ("At ctor exec errno set to %d != 0\n", get_ctor_errno ());
> +      exit (1);

OK. Fails the test.

> +    }
> +
> +  return 0;
> +}
> +

-- 
Cheers,
Carlos.