# truncate.m4 serial 5   -*- Autoconf -*-
dnl Copyright (C) 2017-2023 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

AC_DEFUN([gl_FUNC_TRUNCATE],
[
  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
  AC_REQUIRE([AC_CANONICAL_HOST])

  gl_CHECK_FUNCS_ANDROID([truncate], [[#include <unistd.h>]])
  dnl AC_CHECK_FUNC is not enough here, because when compiling for Android 4.4
  dnl or older with _FILE_OFFSET_BITS=64, truncate() is not declared.  There
  dnl is a function 'truncate' in libc, but it is unsuitable, because it takes
  dnl only a 32-bit offset argument.
  AC_CHECK_DECL([truncate], , , [[#include <unistd.h>]])
  if test $ac_cv_have_decl_truncate = yes; then
    m4_ifdef([gl_LARGEFILE], [
      case "$host_os" in
        mingw*)
          dnl Native Windows, and Large File Support is requested.
          dnl The mingw64 truncate64() function is based on ftruncate64(),
          dnl which is unreliable (it may delete the file, see
          dnl <https://web.archive.org/web/20160425005423/http://mingw-w64.sourcearchive.com/documentation/2.0-1/ftruncate64_8c_source.html>).
          dnl Use gnulib's ftruncate() and truncate() implementation instead.
          REPLACE_TRUNCATE=1
          ;;
      esac
    ], [
      :
    ])
    if test $REPLACE_TRUNCATE = 0; then
      dnl Check for AIX 7.2 bug with trailing slash.
      AC_CACHE_CHECK([whether truncate rejects trailing slashes],
        [gl_cv_func_truncate_works],
        [echo foo > conftest.tmp
         AC_RUN_IFELSE(
           [AC_LANG_PROGRAM(
              [[#include <unistd.h>
              ]],
              [[int result = 0;
                if (!truncate ("conftest.tmp/", 2))
                  result |= 1;
                return result;
              ]])
           ],
           [gl_cv_func_truncate_works=yes],
           [gl_cv_func_truncate_works=no],
           [case "$host_os" in
                               # Guess yes on Linux systems.
              linux-* | linux) gl_cv_func_truncate_works="guessing yes" ;;
                               # Guess yes on glibc systems.
              *-gnu* | gnu*)   gl_cv_func_truncate_works="guessing yes" ;;
                               # Guess no on AIX systems.
              aix*)            gl_cv_func_truncate_works="guessing no" ;;
                               # If we don't know, obey --enable-cross-guesses.
              *)               gl_cv_func_truncate_works="$gl_cross_guess_normal" ;;
            esac
           ])
         rm -f conftest.tmp
        ])
      case "$gl_cv_func_truncate_works" in
        *yes) ;;
        *)
           AC_DEFINE([TRUNCATE_TRAILING_SLASH_BUG], [1],
             [Define to 1 if truncate mishandles trailing slash.])
           REPLACE_TRUNCATE=1
           ;;
      esac
    fi
  else
    HAVE_DECL_TRUNCATE=0
    case "$gl_cv_onwards_func_truncate" in
      dnl Avoid a conflict with the 'truncate' in libc.
      yes | future*) REPLACE_TRUNCATE=1 ;;
    esac
  fi
])

# Prerequisites of lib/truncate.c.
AC_DEFUN([gl_PREREQ_TRUNCATE], [:])