?RCS:
?RCS: $Id$
?RCS:
?RCS: Copyright (c) 2000, Jarkko Hietaniemi
?RCS: 
?X: 
?X: This unit produces a bit of shell code that must be dotted in order
?X: to make quick check on whether the current C compiler is working.
?X:	
?MAKE:Checkcc ccname ccversion: rm cat test Myread startsh
?MAKE:	-pick add $@ %<
?S:ccname:
?S:	This can set either by hints files or by Configure.  If using
?S:	gcc, this is gcc, and if not, usually equal to cc, unimpressive, no?
?S:	Some platforms, however, make good use of this by storing the
?S:	flavor of the C compiler being used here.  For example if using
?S:	the Sun WorkShop suite, ccname will be 'workshop'.
?S:.
?S:ccversion:
?S:	This can set either by hints files or by Configure.  If using
?S:	a (non-gcc) vendor cc, this variable may contain a version for
?S:	the compiler.
?S:.
?T: trygcc despair
?F:./checkcc
?F:./trygcc
?INIT:ccname=''
?INIT:ccversion=''
?LINT:extern cc
?LINT:change cc
?LINT:extern ccflags
?LINT:change ccflags
?LINT:extern ccflags
?LINT:extern ldflags
: Check what type of C compiler we use
cat <<EOS >trygcc
$startsh
EOS
cat <<'EOSC' >>trygcc
case "$cc" in
'') ;;
*)  $rm -f try try.*
    $cat >try.c <<EOM
int main(int argc, char *argv[]) {
  return 0;
}
EOM
    if $cc -o try $ccflags $ldflags try.c; then
       :
    else
        echo "Uh-oh, the C compiler '$cc' doesn't seem to be working." >&4
        despair=yes
        trygcc=yes
        case "$cc" in
        *gcc*) trygcc=no ;;
        esac
	# Skip this test because it gives a false match on output like:
	#    ./trygcc: line 23: cc: command not found
        # case "`$cc -v -c try.c 2>&1`" in
        # *gcc*) trygcc=no ;;
        # esac
        if $test X"$trygcc" = Xyes; then
            if gcc -o try -c try.c; then
                echo " "
                echo "You seem to have a working gcc, though." >&4
		# Switching compilers may undo the work of hints files.
		# The most common problem is -D_REENTRANT for threads.
		# This heuristic catches that case, but gets false positives
		# if -Dusethreads was not actually specified.  Better to
		# bail out here with a useful message than fail 
		# mysteriously later. Should we perhaps just try to
		# re-invoke Configure -Dcc=gcc config_args ?
		if $test -f usethreads.cbu; then
			$cat >&4 <<EOM 

*** However, any setting of the C compiler flags (e.g. for thread support)
*** will be lost.  It may be necessary for you to restart Configure and
*** add -Dcc=gcc to your Configure command line.

EOM
			rp="Would you like to go ahead and try gcc anyway?"
			dflt=n
		else
			rp="Would you like to use it?"
			dflt=y
		fi
                if $test -f myread; then
                    . ./myread
                else
                    if $test -f UU/myread; then
                        . ./UU/myread
                    else
                        echo "Cannot find myread, sorry.  Aborting." >&2
                        exit 1
                    fi
                fi  
                case "$ans" in
                [yY]*) cc=gcc; ccname=gcc; ccflags=''; despair=no;
                esac
            fi
        fi
    fi
    $rm -f try try.*
    ;;
esac
EOSC

cat <<EOS >checkcc
$startsh
EOS
cat <<'EOSC' >>checkcc
case "$cc" in        
'') ;;
*)  $rm -f try try.*              
    $cat >try.c <<EOM
int main(int argc, char *argv[]) {
  return 0;
}
EOM
    if $cc -o try $ccflags $ldflags try.c; then
       :
    else
        if $test X"$despair" = Xyes; then
           echo "Uh-oh, the C compiler '$cc' doesn't seem to be working." >&4
        fi
        $cat >&4 <<EOM         
You need to find a working C compiler.
Either (purchase and) install the C compiler supplied by your OS vendor,
or for a free C compiler try http://gcc.gnu.org/
I cannot continue any further, aborting.
EOM
        exit 1
    fi
    $rm -f try try.*
    ;;
esac
EOSC