1 files changed, 60 insertions, 0 deletions
diff --git a/m4/size_max.m4 b/m4/size_max.m4
new file mode 100644
index 00000000..029e4719
--- /dev/null
+++ b/m4/size_max.m4
@@ -0,0 +1,60 @@
+# size_max.m4 serial 4
+dnl Copyright (C) 2003, 2005-2006 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_DEFUN([gl_SIZE_MAX],
+[
+  AC_CHECK_HEADERS(stdint.h)
+  dnl First test whether the system already has SIZE_MAX.
+  AC_MSG_CHECKING([for SIZE_MAX])
+  result=
+  AC_EGREP_CPP([Found it], [
+#include <limits.h>
+#if HAVE_STDINT_H
+#include <stdint.h>
+#endif
+#ifdef SIZE_MAX
+Found it
+#endif
+], result=yes)
+  if test -z "$result"; then
+    dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
+    dnl than the type 'unsigned long'. Try hard to find a definition that can
+    dnl be used in a preprocessor #if, i.e. doesn't contain a cast.
+    _AC_COMPUTE_INT([sizeof (size_t) * CHAR_BIT - 1], size_t_bits_minus_1,
+      [#include <stddef.h>
+#include <limits.h>], size_t_bits_minus_1=)
+    _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint,
+      [#include <stddef.h>], fits_in_uint=)
+    if test -n "$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_TRY_COMPILE([#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
+        result="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)"
+      else
+        result="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)"
+      fi
+    else
+      dnl Shouldn't happen, but who knows...
+      result='((size_t)~(size_t)0)'
+    fi
+  fi
+  AC_MSG_RESULT([$result])
+  if test "$result" != yes; then
+    AC_DEFINE_UNQUOTED([SIZE_MAX], [$result],
+      [Define as the maximum value of type 'size_t', if the system doesn't define it.])
+  fi
+])