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Message-ID: <4F9852C9.3070106@barfooze.de>
Date: Wed, 25 Apr 2012 21:38:49 +0200
From: John Spencer <maillist-apr@barfooze.de>
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To: dev@apr.apache.org
Subject: broken ac_fn_c_check_type function in configure script
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this check has 2 issues:
a) it does the check twice if the first test succeeds, wasting precious time
b) it uses sizeof(( $2 )) in the second ac_fn_c_try_compile invocation 
which is invalid C

root:/src$ cat test.c
typedef unsigned long size_t;
int main () {
if (sizeof ((size_t)))
       return 0;
     return 0;
}
root:/src$ gcc test.c
test.c: In function 'main':
test.c:3:22: error: expected expression before ')' token

here's the extracted function from version 1.4.6 configure script

# -------------------------------------------
# Tests whether TYPE exists after having included INCLUDES, setting cache
# variable VAR accordingly.
ac_fn_c_check_type ()
{
   as_lineno=${as_lineno-"$1"} 
as_lineno_stack=as_lineno_stack=$as_lineno_stack
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $2" >&5
$as_echo_n "checking for $2... " >&6; }
if eval \${$3+:} false; then :
   $as_echo_n "(cached) " >&6
else
   eval "$3=no"
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h.  */
$4
int
main ()
{
if (sizeof ($2))
          return 0;
   ;
   return 0;
}
_ACEOF
if ac_fn_c_try_compile "$LINENO"; then :
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h.  */
$4
int
main ()
{
if (sizeof (($2)))
             return 0;
   ;
   return 0;
}
_ACEOF
if ac_fn_c_try_compile "$LINENO"; then :

else
   eval "$3=yes"
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
fi
eval ac_res=\$$3
                { $as_echo "$as_me:${as_lineno-$LINENO}: result: 
$ac_res" >&5
$as_echo "$ac_res" >&6; }
   eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno

} # ac_fn_c_check_type

--JS