1 files changed, 75 insertions, 0 deletions
diff --git a/gl/m4/size_max.m4 b/gl/m4/size_max.m4
new file mode 100644
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+++ b/gl/m4/size_max.m4
@@ -0,0 +1,75 @@
+# size_max.m4 serial 11
+dnl Copyright (C) 2003, 2005-2006, 2008-2019 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.
+
+dnl From Bruno Haible.
+
+AC_PREREQ([2.61])
+
+AC_DEFUN([gl_SIZE_MAX],
+[
+  AC_CHECK_HEADERS([stdint.h])
+  dnl First test whether the system already has SIZE_MAX.
+  AC_CACHE_CHECK([for SIZE_MAX], [gl_cv_size_max], [
+    gl_cv_size_max=
+    AC_EGREP_CPP([Found it], [
+#include <limits.h>
+#if HAVE_STDINT_H
+#include <stdint.h>
+#endif
+#ifdef SIZE_MAX
+Found it
+#endif
+], [gl_cv_size_max=yes])
+    if test -z "$gl_cv_size_max"; then
+      dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
+      dnl than the type 'unsigned long'. Try hard to find a definition that can
+      dnl be used in a preprocessor #if, i.e. doesn't contain a cast.
+      AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1],
+        [#include <stddef.h>
+#include <limits.h>], [size_t_bits_minus_1=])
+      AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)],
+        [#include <stddef.h>], [fits_in_uint=])
+      if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then
+        if test $fits_in_uint = 1; then
+          dnl Even though SIZE_MAX fits in an unsigned int, it must be of type
+          dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'.
+          AC_COMPILE_IFELSE(
+            [AC_LANG_PROGRAM(
+               [[#include <stddef.h>
+                 extern size_t foo;
+                 extern unsigned long foo;
+               ]],
+               [[]])],
+            [fits_in_uint=0])
+        fi
+        dnl We cannot use 'expr' to simplify this expression, because 'expr'
+        dnl works only with 'long' integers in the host environment, while we
+        dnl might be cross-compiling from a 32-bit platform to a 64-bit platform.
+        if test $fits_in_uint = 1; then
+          gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)"
+        else
+          gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)"
+        fi
+      else
+        dnl Shouldn't happen, but who knows...
+        gl_cv_size_max='((size_t)~(size_t)0)'
+      fi
+    fi
+  ])
+  if test "$gl_cv_size_max" != yes; then
+    AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max],
+      [Define as the maximum value of type 'size_t', if the system doesn't define it.])
+  fi
+  dnl Don't redefine SIZE_MAX in config.h if config.h is re-included after
+  dnl <stdint.h>. Remember that the #undef in AH_VERBATIM gets replaced with
+  dnl #define by AC_DEFINE_UNQUOTED.
+  AH_VERBATIM([SIZE_MAX],
+[/* Define as the maximum value of type 'size_t', if the system doesn't define
+   it. */
+#ifndef SIZE_MAX
+# undef SIZE_MAX
+#endif])
+])