libast: fix memccpy(3) feature test

If you passed CC=/some/compiler, the build broke on macOS because the
cc.darwin compiler wrapper wasn't used. Among other things, this
wrapper adds a -D_lib_memccpy flag, defining _lib_memccpy as 1
during the build. That was used to override a false negative result
of the lib_memccpy feature test. This commit fixes that feature
test instead, so it correctly returns positive on macOS.

Thanks to Ryan Smith (@ryandesign) for the bug report and for the
fix to the lib_memccpy test.

src/lib/libast/features/lib:
- Fix the lib_memccpy feature test. It was checking the result of
  mmap(2) incorrectly, resulting in the test crashing on macOS.
  Failure does not return NULL, it returns MAP_FAILED which is
  usually -1.

src/cmd/INIT/cc.darwin*:
- Removed. Any other flags in these wrappers are either related to
  building dynamic libraries, which is not currently supported, or
  were determined to be unnecessary. See the GitHub issue for
  discussion. This now makes it possible to pass `CC` to use any
  compiler you like on the Mac. Notes:
  - Apple's -D_ast_int8_t=int64_t is a no-op; another AST feature
    test already defines _ast_int8_t a 64-bit integer type, even on
    32-bit systems (on which it is defined as 'long long').
  - The -search_paths_first linker flag is the default since 2010.
    But even on my museum-grade Power Mac G5 with Mac OS X 10.3
    (from 2004), it builds and runs just fine without.
  - DCLK_TCK=100 is a no-op as even that ancient Mac system already
    defines it as 100. Plus, it's not even actually used.
  If a need is found for any of these, please report this in a new
  issue so I can special-case it elsewhere in the code.

Resolves: https://github.com/ksh93/ksh/issues/373

src/cmd/INIT/cc.darwin

@@ -1,52 +0,0 @@
-: unix wrapper for macOS cc : 2020-07-17 :
-
-HOSTTYPE=darwin.generic
-
-case " $* " in
-*" -dumpmachine "*) echo $HOSTTYPE; exit ;;
-esac
-
-CC=/usr/bin/cc
-op=init
-for arg
-do	case $op in
-	init)	op=ld
-		set ''
-		;;
-	esac
-	case $arg in
-	-c)	op=cc
-		;;
-	-E)	op=cpp
-		continue
-		;;
-	-G)	op=dll
-		continue
-		;;
-	-lc)	continue
-		;;
-	-lm)	continue
-		;;
-	esac
-	set "$@" "$arg"
-done
-case $# in
-0)	;;
-*)	shift ;;
-esac
-case $* in
--v)	$CC "$@"; exit ;;
-esac
-case $op in
-init)	echo "cc: arguments expected" >&2
-	exit 1
-	;;
-cpp)	$CC -E "$@"
-	;;
-cc)	$CC -D_ast_int8_t=int64_t -D_lib_memccpy "$@"
-	;;
-dll)	$CC -Wl,-flat_namespace -dynamiclib -undefined dynamic_lookup "$@"
-	;;
-ld)	$CC -Wl,-search_paths_first "$@"
-	;;
-esac

src/cmd/INIT/cc.darwin07

@@ -1,71 +0,0 @@
-: unix wrapper for Mac OS X 10.3-10.6 (Darwin 7-10) cc : 2020-07-17 :
-
-HOSTTYPE=darwin07.generic
-
-case " $* " in
-*" -dumpmachine "*) echo $HOSTTYPE; exit ;;
-esac
-
-CC=/usr/bin/cc
-op=init
-for arg
-do	case $op in
-	init)	op=ld
-		set ''
-		;;
-	esac
-	case $arg in
-	-c)	op=cc
-		;;
-	-E)	op=cpp
-		continue
-		;;
-	-G)	op=dll
-		continue
-		;;
-	-lc)	continue
-		;;
-	-lm)	continue
-		;;
-	esac
-	set "$@" "$arg"
-done
-case $# in
-0)	;;
-*)	shift ;;
-esac
-case $* in
--v)	$CC "$@"; exit ;;
-esac
-case $op in
-init)	echo "cc: arguments expected" >&2
-	exit 1
-	;;
-cpp)	$CC -E "$@"
-	;;
-cc)	$CC -DCLK_TCK=100 "$@"
-	;;
-dll)	# what a compatibility mess -- surely they can get the apis to play nice
-	tmp=/tmp/cc.${USER:-$LOGNAME}.$$.err
-	trap "rm -f $tmp" EXIT
-	case `MACOSX_DEPLOYMENT_TARGET=10.3 ld -undefined dynamic_lookup 2>&1` in
-	*undefined*dynamic_lookup*)
-		ld -m -flat_namespace -undefined suppress -dylib -dynamic \
-			-ldylib1.o "$@" -lcc_dynamic -framework System >$tmp 2>&1
-		status=$?
-		;;
-	*)	MACOSX_DEPLOYMENT_TARGET=10.3 $CC -Wl,-flat_namespace -dynamiclib -undefined dynamic_lookup "$@" >$tmp 2>&1
-		status=$?
-		;;
-	esac
-	egrep -v ' (warning .*multiple definitions|definition) of ' $tmp >&2
-	exit $status
-	;;
-ld)	tmp=/tmp/cc.${USER:-$LOGNAME}.$$.err
-	trap "rm -f $tmp" EXIT
-	$CC -Wl,-m -DCLK_TCK=100 "$@" >$tmp 2>&1
-	status=$?
-	egrep -v ' (warning .*multiple definitions of|definition of|as lazy binding|not from earlier dynamic) ' $tmp >&2
-	exit $status
-	;;
-esac

src/cmd/INIT/cc.darwin11

@@ -1,71 +0,0 @@
-: unix wrapper for Mac OS X 10.7 (Darwin 11) cc : 2020-07-17 :
-
-HOSTTYPE=darwin11.generic
-
-case " $* " in
-*" -dumpmachine "*) echo $HOSTTYPE; exit ;;
-esac
-
-CC=/usr/bin/cc
-op=init
-for arg
-do	case $op in
-	init)	op=ld
-		set ''
-		;;
-	esac
-	case $arg in
-	-c)	op=cc
-		;;
-	-E)	op=cpp
-		continue
-		;;
-	-G)	op=dll
-		continue
-		;;
-	-lc)	continue
-		;;
-	-lm)	continue
-		;;
-	esac
-	set "$@" "$arg"
-done
-case $# in
-0)	;;
-*)	shift ;;
-esac
-case $* in
--v)	$CC "$@"; exit ;;
-esac
-case $op in
-init)	echo "cc: arguments expected" >&2
-	exit 1
-	;;
-cpp)	$CC -E "$@"
-	;;
-cc)	$CC -DCLK_TCK=100 "$@"
-	;;
-dll)	# what a compatibility mess -- surely they can get the apis to play nice
-	tmp=/tmp/cc.${USER:-$LOGNAME}.$$.err
-	trap "rm -f $tmp" EXIT
-	case `MACOSX_DEPLOYMENT_TARGET=10.7 ld -undefined dynamic_lookup 2>&1` in
-	*undefined*dynamic_lookup*)
-		ld -m -flat_namespace -undefined suppress -dylib -dynamic \
-			-ldylib1.o "$@" -lcc_dynamic -framework System >$tmp 2>&1
-		status=$?
-		;;
-	*)	MACOSX_DEPLOYMENT_TARGET=10.7 $CC -Wl,-flat_namespace -dynamiclib -undefined dynamic_lookup "$@" >$tmp 2>&1
-		status=$?
-		;;
-	esac
-	egrep -v ' (warning .*multiple definitions|definition) of ' $tmp >&2
-	exit $status
-	;;
-ld)	tmp=/tmp/cc.${USER:-$LOGNAME}.$$.err
-	trap "rm -f $tmp" EXIT
-	$CC -Wl,-m -DCLK_TCK=100 "$@" >$tmp 2>&1
-	status=$?
-	egrep -v ' (warning .*multiple definitions of|definition of|as lazy binding|not from earlier dynamic) ' $tmp >&2
-	exit $status
-	;;
-esac

src/lib/libast/features/lib

@@ -446,6 +446,9 @@ tst	lib_memcmp string.h note{ standard memcmp interface that works }end execute{
 }end
 
 tst	lib_memccpy string.h unistd.h stdlib.h fcntl.h signal.h sys/types.h sys/stat.h sys/mman.h fcntl.h note{ standard memccpy interface that works }end execute{
+	#ifndef MAP_FAILED
+	#define MAP_FAILED ((void*)-1)	/* introduced in POSIX-1.2017 */
+	#endif
 	#if _STD_
 	static void gotcha(int sig)
 	#else
@@ -490,7 +493,7 @@ tst	lib_memccpy string.h unistd.h stdlib.h fcntl.h signal.h sys/types.h sys/stat
 			return 1;
 		}
 		m = n * (sizeof(x)-1);
-		if (!(b = mmap((void*)0, m, PROT_READ|PROT_WRITE, MAP_PRIVATE, d, (off_t)0)))
+		if ((b = mmap((void*)0, m, PROT_READ|PROT_WRITE, MAP_PRIVATE, d, (off_t)0)) == MAP_FAILED)
 		{
 			close(d);
 			return 1;
@@ -544,9 +547,9 @@ tst	lib_memccpy string.h unistd.h stdlib.h fcntl.h signal.h sys/types.h sys/stat
 			return 0;
 		if ((fd = open("/dev/zero", O_RDWR)) < 0)
 			return 0;
-		if (!(srcbuf = (char*)mmap(NULL, siz, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0)))
+		if ((srcbuf = (char*)mmap(NULL, siz, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0)) == MAP_FAILED)
 			return 0;
-		if (!mmap(srcbuf + siz, siz, PROT_NONE, MAP_PRIVATE, fd, 0))
+		if (mmap(srcbuf + siz, siz, PROT_NONE, MAP_PRIVATE, fd, 0) == MAP_FAILED)
 			return 0;
 		for (i = 0; i < siz; i++)
 			srcbuf[i] = 'x';