File: ac_define_integer_bits.html

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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
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  <title>
   Autoconf Macro: ac_define_integer_bits
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  <hr>
  <h1>
   ac_define_integer_bits
  </h1>
  <h2>
   Synopsis
  </h2>
  <p class="indent" style="white-space:nowrap;">
   <code>AC_DEFINE_INTEGER_BITS (TYPE [, CANDIDATE-TYPE]...)</code>
  </p>
  <h2>
   Description
  </h2>
  <div class="indent">
   <p>
    Given a TYPE of the form "int##_t" or "uint##_t", see if the datatype TYPE
    is predefined. If not, then define TYPE -- both with AC_DEFINE and as a
    shell variable -- to the first datatype of exactly ## bits in a list of
    CANDIDATE-TYPEs. If none of the CANDIDATE-TYPEs contains exactly ## bits,
    then set the TYPE shell variable to "no".
   </p>
   <p>
    For example, the following ensures that uint64_t is defined as a 64-bit
    datatype:
   </p>
   <pre>
    AC_DEFINE_INTEGER_BITS(uint64_t, unsigned long long, unsigned __int64, long)
    if test "$uint64_t" = no; then
      AC_MSG_ERROR([unable to continue without a 64-bit datatype])
    fi
</pre>
   <p>
    You should then put the following in your C code to ensure that all
    datatypes defined by AC_DEFINE_INTEGER_BITS are visible to your program:
   </p>
   <pre>
    #include "config.h"

    #if HAVE_INTTYPES_H
    # include &lt;inttypes.h&gt;
    #else
    # if HAVE_STDINT_H
    #  include &lt;stdint.h&gt;
    # endif
    #endif
</pre>
  </div>
  <h2>
   Author
  </h2>
  <p class="indent">
   Scott Pakin &lt;pakin@uiuc.edu&gt;
  </p>
  <h2>
   Last Modified
  </h2>
  <p class="indent">
   2002-01-31
  </p>
  <h2>
   M4 Source Code
  </h2>
  <div class="indent">
   <pre class="m4source">
AC_DEFUN([AC_DEFINE_INTEGER_BITS],
[m4_define([ac_datatype_bits], [m4_translit($1, [a-zA-Z_])])
m4_define([ac_datatype_bytes], [m4_eval(ac_datatype_bits/8)])
AC_CHECK_TYPE($1, ,
 [
  AC_MSG_NOTICE([trying to find a suitable ]ac_datatype_bytes[-byte replacement for $1])
  $1=no
  find_$1 ()
  {
    _AC_DEFINE_INTEGER_BITS_HELPER($@)
    :
  }
  find_$1
  AC_DEFINE_UNQUOTED($1, $$1,
    [If not already defined, then define as a datatype of *exactly* ]ac_datatype_bits[ bits.])
 ])
])

dnl Iterate over arguments $2..$N, trying to find a good match for $1.
m4_define([_AC_DEFINE_INTEGER_BITS_HELPER],
[ifelse($2, , ,
 [m4_define([ac_datatype_bits], [m4_translit($1, [a-zA-Z_])])
  m4_define([ac_datatype_bytes], [m4_eval(ac_datatype_bits/8)])
  AC_CHECK_SIZEOF($2)
  if test "$AS_TR_SH(ac_cv_sizeof_$2)" -eq ac_datatype_bytes; then
    $1="$2"
    return
  fi
  _AC_DEFINE_INTEGER_BITS_HELPER($1, m4_shift(m4_shift($@)))
 ])
])
</pre>
  </div>
  <h2>
   License
  </h2>
  <div class="indent">
   <span style="white-space:nowrap;">Copyright &copy; 2002 Scott Pakin
   &lt;pakin@uiuc.edu&gt;</span>
   <p>
    Copying and distribution of this file, with or without modification, are
    permitted in any medium without royalty provided the copyright notice and
    this notice are preserved.
   </p>
  </div>
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