?RCS: $Id: Csym.U 167 2013-05-08 17:58:00Z rmanfredi $
?RCS:
?RCS: Copyright (c) 1991-1997, 2004-2006, Raphael Manfredi
?RCS: 
?RCS: You may redistribute only under the terms of the Artistic License,
?RCS: as specified in the README file that comes with the distribution.
?RCS: You may reuse parts of this distribution only within the terms of
?RCS: that same Artistic License; a copy of which may be found at the root
?RCS: of the source tree for dist 4.0.
?RCS:
?RCS: $Log: Csym.U,v $
?RCS: Revision 3.0.1.4  1995/07/25  13:36:29  ram
?RCS: patch56: re-arranged compile line to include ldflags before objects
?RCS: patch56: added quotes for OS/2 support
?RCS:
?RCS: Revision 3.0.1.3  1995/05/12  12:00:33  ram
?RCS: patch54: fixed C test program to bypass gcc builtin type checks (ADO)
?RCS:
?RCS: Revision 3.0.1.2  1994/10/31  09:34:13  ram
?RCS: patch44: added Options to the MAKE line since it's no longer in Init.U
?RCS:
?RCS: Revision 3.0.1.1  1993/08/25  14:00:05  ram
?RCS: patch6: added ldflags as a conditional dependency and to compile line
?RCS: patch6: a final double quote was missing in csym variable after eval
?RCS:
?RCS: Revision 3.0  1993/08/18  12:04:50  ram
?RCS: Baseline for dist 3.0 netwide release.
?RCS:
?MAKE:Csym: Options contains cat libc libs runnm +cc +ccflags +ldflags rm
?MAKE:	-pick add $@ %<
?LINT:define csym
?LINT:use libc
?S:csym:
?S:	This shell variable is used internally by Configure to check
?S:	wether a given C symbol is defined or not. A typical use is:
?S:		set symbol result [-fva] [previous]
?S:		eval $csym
?S:	That will set result to 'true' if the function [-f], variable [-v]
?S:	or array [-a] is defined, 'false' otherwise. If a previous value is
?S:	given and the -r flag was provided on the command line, that value
?S:	is reused without questioning.
?S:.
?V:csym
?T:tval tx tlook tf tdc tc file
: is a C symbol defined?
csym='tlook=$1;
case "$3" in
-v) tf=libc.tmp; tc=""; tdc="";;
-a) tf=libc.tmp; tc="[0]"; tdc="[]";;
*) tlook="^$1\$"; tf=libc.list; tc=""; tdc="()";;
esac;
file=csym.log;
tx=yes;
case "$reuseval-$4" in
true-) ;;
true-*) tx=no; eval "tval=\$$4"; case "$tval" in "") tx=yes;; esac;;
esac;
case "$tx" in
yes)
	case "$runnm" in
	true)
		if $contains $tlook $tf >/dev/null 2>&1;
		then tval=true;
		else tval=false;
		fi;;
	*)
?X:
?X: We use 'char' instead of 'int' to try to circumvent overzealous
?X: optimizing compilers using built-in prototypes for commonly used
?X: routines to complain when seeing a different external declaration. For
?X: instance, gcc 2.6.3 fails if we use 'int' and we attempt a test against
?X: memcpy() on machines where sizeof(int) == sizeof(char *) (the usual return
?X: type), the compiler assuming it's a built-in declaration given that the
?X: returned size matches. At least with 'char' we are safe! -- RAM, for ADO
?X:
?X: Let's thank GNU cc for making our lives so easy! :-)
?X: (An alternative for the future would be to use our knowledge about gcc
?X: to force a -fno-builtin option in the compile test, in case the 'char'
?X: trick is obsoleted by future gcc releases). -- RAM
?X:
?X: Lastly, gcc 3.4 optimizes &missing == 0 away, so we use + 2 instead now.
?X: The GNU folks like to do weird things, don't they? -- RAM, 2004-06-05
?X
?X: The above was invalid because main returns an int not a pointer.
?X: Using != or == does not work because GCC complains the pointer will
?X: never be NULL if the function exists. It is a warning meant to prevent
?X: using an address of a function by accident instead of calling it.
?X: However, &missing > 0 is indeed silently optimized away.
?X
?X: FIXME: There must be a test whether non-existing functions are found!
?X:
?X:. -- cbiere, 2011-01-18
?X:
		echo "--- $1$tdc ---" >> "$file";
		echo "extern char $1$tdc; int main(void) { return (unsigned long) &$1$tc > 2; }" > t.c;
		$cat t.c >> "$file";
		if $cc $ccflags $ldflags -o t t.c $libs >>"$file" 2>&1;
		then tval=true;
		else tval=false;
		fi;
		$rm -f t t.c;;
	esac;;
*)
	case "$tval" in
	$define) tval=true;;
	*) tval=false;;
	esac;;
esac;
echo "==> HAS $1$tdc is $tval ($4)" >>"$file";
eval "$2=$tval"'