emacs/m4/realloc.m4

# realloc.m4 serial 26
dnl Copyright (C) 2007, 2009-2022 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.

# This is adapted with modifications from upstream Autoconf here:
# https://git.savannah.gnu.org/cgit/autoconf.git/tree/lib/autoconf/functions.m4?id=v2.70#n1455
AC_DEFUN([_AC_FUNC_REALLOC_IF],
[
  AC_REQUIRE([AC_CANONICAL_HOST])dnl for cross-compiles
  AC_CACHE_CHECK([whether realloc (0, 0) returns nonnull],
    [ac_cv_func_realloc_0_nonnull],
    [AC_RUN_IFELSE(
       [AC_LANG_PROGRAM(
          [[#include <stdlib.h>
          ]],
          [[void *p = realloc (0, 0);
            int result = !p;
            free (p);
            return result;]])
       ],
       [ac_cv_func_realloc_0_nonnull=yes],
       [ac_cv_func_realloc_0_nonnull=no],
       [case "$host_os" in
          # Guess yes on platforms where we know the result.
          *-gnu* | freebsd* | netbsd* | openbsd* | bitrig* \
          | gnu* | *-musl* | midnightbsd* \
          | hpux* | solaris* | cygwin* | mingw* | msys* )
            ac_cv_func_realloc_0_nonnull="guessing yes" ;;
          # If we don't know, obey --enable-cross-guesses.
          *) ac_cv_func_realloc_0_nonnull="$gl_cross_guess_normal" ;;
        esac
       ])
    ])
  AS_CASE([$ac_cv_func_realloc_0_nonnull], [*yes], [$1], [$2])
])# AC_FUNC_REALLOC

# gl_FUNC_REALLOC_GNU
# -------------------
# Replace realloc if it is not compatible with GNU libc.
AC_DEFUN([gl_FUNC_REALLOC_GNU],
[
  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
  AC_REQUIRE([gl_FUNC_REALLOC_POSIX])
  if test $REPLACE_REALLOC_FOR_REALLOC_GNU = 0; then
    _AC_FUNC_REALLOC_IF([], [REPLACE_REALLOC_FOR_REALLOC_GNU=1])
  fi
])# gl_FUNC_REALLOC_GNU

# gl_FUNC_REALLOC_POSIX
# ---------------------
# Test whether 'realloc' is POSIX compliant (sets errno to ENOMEM when it
# fails, and doesn't mess up with ptrdiff_t overflow),
# and replace realloc if it is not.
AC_DEFUN([gl_FUNC_REALLOC_POSIX],
[
  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
  AC_REQUIRE([gl_FUNC_MALLOC_POSIX])
  if test $REPLACE_MALLOC_FOR_MALLOC_POSIX = 1; then
    REPLACE_REALLOC_FOR_REALLOC_POSIX=1
  fi
])