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diff --git a/gl/m4/calloc.m4 b/gl/m4/calloc.m4
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+# calloc.m4 serial 27
+
+# Copyright (C) 2004-2021 Free Software Foundation, Inc.
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+# Written by Jim Meyering.
+
+# Determine whether calloc (N, S) returns non-NULL when N*S is zero,
+# and returns NULL when N*S overflows.
+# If so, define HAVE_CALLOC.  Otherwise, define calloc to rpl_calloc
+# and arrange to use a calloc wrapper function that does work in that case.
+
+# _AC_FUNC_CALLOC_IF([IF-WORKS], [IF-NOT])
+# -------------------------------------
+# If calloc is compatible with GNU calloc, run IF-WORKS, otherwise, IF-NOT.
+AC_DEFUN([_AC_FUNC_CALLOC_IF],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  AC_CACHE_CHECK([whether calloc (0, n) and calloc (n, 0) return nonnull],
+    [ac_cv_func_calloc_0_nonnull],
+    [if test $cross_compiling != yes; then
+       ac_cv_func_calloc_0_nonnull=yes
+       AC_RUN_IFELSE(
+         [AC_LANG_PROGRAM(
+            [AC_INCLUDES_DEFAULT],
+            [[int result = 0;
+              char * volatile p = calloc (0, 0);
+              if (!p)
+                result |= 1;
+              free (p);
+              return result;
+            ]])],
+         [],
+         [ac_cv_func_calloc_0_nonnull=no])
+     else
+       case "$host_os" in
+                        # Guess yes on glibc systems.
+         *-gnu* | gnu*) ac_cv_func_calloc_0_nonnull="guessing yes" ;;
+                        # Guess yes on musl systems.
+         *-musl*)       ac_cv_func_calloc_0_nonnull="guessing yes" ;;
+                        # Guess yes on native Windows.
+         mingw*)        ac_cv_func_calloc_0_nonnull="guessing yes" ;;
+                        # If we don't know, obey --enable-cross-guesses.
+         *)             ac_cv_func_calloc_0_nonnull="$gl_cross_guess_normal" ;;
+       esac
+     fi
+    ])
+  AS_CASE([$ac_cv_func_calloc_0_nonnull], [*yes], [$1], [$2])
+])
+
+
+# gl_FUNC_CALLOC_GNU
+# ------------------
+# Replace calloc if it is not compatible with GNU libc.
+AC_DEFUN([gl_FUNC_CALLOC_GNU],
+[
+  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+  AC_REQUIRE([gl_FUNC_CALLOC_POSIX])
+  if test $REPLACE_CALLOC = 0; then
+    _AC_FUNC_CALLOC_IF([], [REPLACE_CALLOC=1])
+  fi
+])# gl_FUNC_CALLOC_GNU
+
+# gl_FUNC_CALLOC_POSIX
+# --------------------
+# Test whether 'calloc' is POSIX compliant (sets errno to ENOMEM when it
+# fails, and doesn't mess up with ptrdiff_t or size_t overflow),
+# and replace calloc if it is not.
+AC_DEFUN([gl_FUNC_CALLOC_POSIX],
+[
+  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+  AC_REQUIRE([gl_FUNC_MALLOC_POSIX])
+  if test $REPLACE_MALLOC = 1; then
+    REPLACE_CALLOC=1
+  fi
+  dnl Although in theory we should also test for size_t overflow,
+  dnl in practice testing for ptrdiff_t overflow suffices
+  dnl since PTRDIFF_MAX <= SIZE_MAX on all known Gnulib porting targets.
+  dnl A separate size_t test would slow down 'configure'.
+])