glibc/stdio-common/tst-printf-format-vd.h

/* Test feature wrapper for formatted 'vdprintf' output.
   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 <stdarg.h>
#include <stdio.h>
#include <unistd.h>

/* We need to go through the POSIX-mandated dance to switch between
   handles on an open file description.  */

static int
printf_under_test (const char *restrict fmt, ...)
{
  va_list ap;
  int result;

  result = fflush (stdout);
  if (result == EOF)
    {
      perror ("fflush");
      goto out;
    }
  result = lseek (STDOUT_FILENO, 0, SEEK_END);
  if (result < 0 && errno == ESPIPE)
    result = 0;
  if (result < 0)
    {
      perror ("lseek");
      goto out;
    }
  va_start (ap, fmt);
  result = vdprintf (STDOUT_FILENO, fmt, ap);
  va_end (ap);
  if (result < 0)
    {
      perror ("vdprintf");
      goto out;
    }
  result = fseek (stdout, 0, SEEK_END);
  if (result < 0 && errno == ESPIPE)
    result = 0;
  if (result < 0)
    perror ("fseek");
out:
  return result;
}