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+?RCS: $Id: Csym.U,v 1995/07/25 13:36:29 ram Exp $
+?RCS: Copyright (c) 1991-1993, Raphael Manfredi
+?RCS: You may redistribute only under the terms of the Artistic Licence,
+?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 Licence; a copy of which may be found at the root
+?RCS: of the source tree for dist 3.0.
+?RCS: $Log: Csym.U,v $
+?RCS: Revision 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: Revision 1995/05/12 12:00:33 ram
+?RCS: patch54: fixed C test program to bypasss gcc builtin type checks (ADO)
+?RCS: Revision 1994/10/31 09:34:13 ram
+?RCS: patch44: added Options to the MAKE line since it's no longer in Init.U
+?RCS: Revision 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: Revision 3.0 1993/08/18 12:04:50 ram
+?RCS: Baseline for dist 3.0 netwide release.
+?MAKE:Csym: Options contains libc libs runnm +cc +ccflags +ldflags rm
+?MAKE: -pick add $@ %<
+?LINT:define csym
+?LINT:use libc
+?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.
+?T:tval tx tlook tf tdc tc
+: is a C symbol defined?
+case "$3" in
+-v) tf=libc.tmp; tc=""; tdc="";;
+-a) tf=libc.tmp; tc="[0]"; tdc="[]";;
+*) tlook="^$1\$"; tf=libc.list; tc="()"; tdc="()";;
+case "$reuseval-$4" in
+true-) ;;
+true-*) tx=no; eval "tval=\$$4"; case "$tval" in "") tx=yes;; esac;;
+case "$tx" in
+ case "$runnm" in
+ true)
+ if $contains $tlook $tf >/dev/null 2>&1;
+ then tval=true;
+ else tval=false;
+ fi;;
+ *)
+?X: Put symbol inside a printf to fool optimizing compilers...
+?X: We use 'short' 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 'short' we are safe! -- RAM, for ADO
+?X: Let's thank GNU cc for making our lifes 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 'short'
+?X: trick is obsoleted by future gcc releases). -- RAM
+ echo "main() { extern short $1$tdc; printf(\"%hd\", $1$tc); }" > t.c;
+ if $cc $ccflags $ldflags -o t t.c $libs >/dev/null 2>&1;
+ then tval=true;
+ else tval=false;
+ fi;
+ $rm -f t t.c;;
+ esac;;
+ case "$tval" in
+ $define) tval=true;;
+ *) tval=false;;
+ esac;;
+eval "$2=$tval"'