[01/11] support: Add support_copy_file

---
 support/Makefile            |  1 +
 support/support.h           |  5 +++++
 support/support_copy_file.c | 43 +++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+)
 create mode 100644 support/support_copy_file.c

LGTM with a couple nits below.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

On 09/11/2020 15:40, Florian Weimer via Libc-alpha wrote:
> ---
>  support/Makefile            |  1 +
>  support/support.h           |  5 +++++
>  support/support_copy_file.c | 43 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 49 insertions(+)
>  create mode 100644 support/support_copy_file.c
> 
> diff --git a/support/Makefile b/support/Makefile
> index 4154863511..f5f59bf8d2 100644
> --- a/support/Makefile
> +++ b/support/Makefile
> @@ -46,6 +46,7 @@ libsupport-routines = \
>    support_capture_subprocess \
>    support_capture_subprocess_check \
>    support_chroot \
> +  support_copy_file \
>    support_copy_file_range \
>    support_descriptor_supports_holes \
>    support_descriptors \
> diff --git a/support/support.h b/support/support.h
> index 905b5a76d8..abda3a69f1 100644
> --- a/support/support.h
> +++ b/support/support.h
> @@ -119,6 +119,11 @@ extern const char support_install_rootsbindir[];
>  /* Corresponds to the install's compiled locale directory.  */
>  extern const char support_complocaledir_prefix[];
>  
> +/* Copies the file at the path FROM to TO.  If TO does not exist, it
> +   is created.  If TO is a regular file, it is truncated before
> +   copying.  The file mode is copied, but the permissions are not.  */
> +extern void support_copy_file (const char *from, const char *to);
> +
>  extern ssize_t support_copy_file_range (int, off64_t *, int, off64_t *,
>  					size_t, unsigned int);
>  

Ok.

> diff --git a/support/support_copy_file.c b/support/support_copy_file.c
> new file mode 100644
> index 0000000000..bf8f83803a
> --- /dev/null
> +++ b/support/support_copy_file.c
> @@ -0,0 +1,43 @@
> +/* Copy a file from one path to another.
> +   Copyright (C) 2020 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 <fcntl.h>
> +#include <support/check.h>
> +#include <support/support.h>
> +#include <support/xunistd.h>
> +
> +void
> +support_copy_file (const char *from, const char *to)
> +{
> +  struct stat64 st;
> +  xstat (from, &st);
> +  int fd_from = xopen (from, O_RDONLY, 0);
> +  mode_t mode = st.st_mode & 0777;
> +  int fd_to = xopen (to, O_WRONLY | O_TRUNC | O_CREAT, mode);
> +  ssize_t ret = support_copy_file_range (fd_from, NULL, fd_to, NULL,
> +                                         st.st_size, 0);
> +  if (ret < 0)
> +    FAIL_EXIT1 ("copying from \"%s\" to \"%s\": %m", from, to);
> +  if (ret != st.st_size)
> +    FAIL_EXIT1 ("copying from \"%s\" to \"%s\": only %zd of %llu bytes copied",

This line seems too long.

> +                from, to, ret, (unsigned long long int) st.st_size);
> +  if (fchmod (fd_to, mode) < 0)
> +    FAIL_EXIT1 ("fchmod on %s: %m", to);

Maybe put 'to' within quotations as well?

> +  xclose (fd_to);
> +  xclose (fd_from);
> +}
>

* Adhemerval Zanella via Libc-alpha:

>> +  if (ret != st.st_size)
>> +    FAIL_EXIT1 ("copying from \"%s\" to \"%s\": only %zd of %llu bytes copied",
>
> This line seems too long.

It's 79 characters long, which is the maximum according to:

  <https://sourceware.org/glibc/wiki/Style_and_Conventions#A79-Column_Lines>

>> +                from, to, ret, (unsigned long long int) st.st_size);
>> +  if (fchmod (fd_to, mode) < 0)
>> +    FAIL_EXIT1 ("fchmod on %s: %m", to);
>
> Maybe put 'to' within quotations as well?

Thanks, fixed.  Will push if it still builds.

Florian