X-Git-Url: https://git.cworth.org/git?a=blobdiff_plain;f=m4%2Fsize_max.m4;fp=m4%2Fsize_max.m4;h=e0e7b3ff9542839b454870968c510e67d52c5913;hb=785cdec4450a1459fdbb90df1344b69be34e0059;hp=0000000000000000000000000000000000000000;hpb=cf7169a2ede9bb08b71de68fe0c8bbecf827abe6;p=tar

diff --git a/m4/size_max.m4 b/m4/size_max.m4
new file mode 100644
index 0000000..e0e7b3f
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+++ b/m4/size_max.m4
@@ -0,0 +1,68 @@
+# size_max.m4 serial 7
+dnl Copyright (C) 2003, 2005-2006, 2008 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])
+  AC_CACHE_VAL([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_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
+          gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)"
+        else
+          gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)"
+        fi
+      else
+        dnl Shouldn't happen, but who knows...
+        gl_cv_size_max='((size_t)~(size_t)0)'
+      fi
+    fi
+  ])
+  AC_MSG_RESULT([$gl_cv_size_max])
+  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 Autoconf >= 2.61 has AC_COMPUTE_INT built-in.
+dnl Remove this when we can assume autoconf >= 2.61.
+m4_ifdef([AC_COMPUTE_INT], [], [
+  AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])])
+])