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generated...
2007-08-05

(C) 2007 guidod
Download the M4 Source.

ac_prog_cc_char_subscripts

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Synopsis
AC_PROG_CC_CHAR_SUBSCRIPTS(substvar [,hard])
, 
Version

2001-04-27

Author

Guido U. Draheim <guidod@gmx.de>

License

GPLWithACException
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation. As a special exception, the respective Autoconf Macro's copyright owner gives unlimited permission to copy, distribute and modify the configure scripts that are the output of Autoconf when processing the Macro. You need not follow the terms of the GNU General Public License when using or distributing such scripts

Category

guidod's C Support (released)

Documentation

Try to find a compiler option that enables usage of char-type to index a value-field. This one needs unsigned-chars and it must suppress warnings about usage of chars for subscripting. for gcc -funsigned-char -Wno-char-subscripts

Currently this macro knows about GCC. hopefully will evolve to use: Solaris C compiler, Digital Unix C compiler, C for AIX Compiler, HP-UX C compiler, and IRIX C compiler.

M4 Source Code
AC_DEFUN([AC_PROG_CC_CHAR_SUBSCRIPTS], [
  pushdef([CV],ac_cv_prog_cc_char_subscripts)dnl
  hard=$2
  if test -z "$hard"; then
    msg="C to enable char subscripts"
  else
    msg="C to ensure char subscripts"
  fi
  AC_CACHE_CHECK($msg, CV, [
  cat &gt; conftest.c &lt;&lt;EOF
int main (void)
{
   char v = 1;
   int x[[2]] = { 3 , 4 };
   return x[[v]];
}
EOF
  cp conftest.c writetest.c
  dnl GCC
  if test "$GCC" = "yes";
  then
      	if test -z "$hard"; then
      	   CV="-funsigned-char -Wno-char-subscripts"
    	else
      	   CV="-funsigned-char -Wno-char-subscripts"
    	fi

    	if test -n "`${CC-cc} -c $CV conftest.c 2&gt;&amp;1`" ; then
           CV="suppressed: did not work"
    	fi

  dnl Solaris C compiler
	# Solaris sunpro has no option for unsignedchar but
	# signedchar is the default for char. Duhh.

  dnl HP-UX C compiler

  dnl Digital Unix C compiler
  elif ! $CC &gt; /dev/null 2&gt;&amp;1 &amp;&amp;
	$CC -c -unsigned conftest.c &gt; /dev/null 2&gt;&amp;1 &amp;&amp;
	test -f conftest.o
  then
	# char :  unsigned char
	CV="-unsigned"

	rm conftest.o
    	if test -n "`${CC-cc} -c $CV conftest.c 2&gt;&amp;1`" ; then
           CV="suppressed: did not work"
    	fi

  dnl C for AIX Compiler

  dnl IRIX C compiler
	# char is unsigned by default for IRIX C.

  fi
  rm -f conftest.*
  ])
  if test -z "[$]$1" ; then
    if test -n "$CV" ; then
      case "$CV" in
        suppressed*) $1="" ;; # known but suppressed
        *)  $1="$CV" ;;
      esac
    fi
  fi
  AC_SUBST($1)
  popdef([CV])dnl
])