xargs: Limit -n to {ARG_MAX}

Since it's not possible to pass more than {ARG_MAX} bytes on the command
line, it's also not possible to pass more than {ARG_MAX} individual
arguments.  Therefore, {ARG_MAX} is a reasonable upper bound for the -n
option.  This resolves both the arithmetic overflow issue and the CI OOM
issue, so we can safely re-enable the test.

Fixes:		eab91d0081
Fixes:		2682a15527
MFC after:	1 week
Reviewed by:	jlduran, emaste
Differential Revision:	https://reviews.freebsd.org/D51536

ObsoleteFiles.inc

@@ -51,6 +51,9 @@
 #   xargs -n1 | sort | uniq -d;
 # done
 
+# 20250726: Test case renamed
+OLD_FILES+=usr/tests/usr.bin/xargs/regress.n2147483647.out
+
 # 20250726: This file is now installed in /etc/dma
 OLD_FILES+=usr/share/examples/dma/auth.conf
 

usr.bin/xargs/tests/Makefile

@@ -17,7 +17,7 @@ ${PACKAGE}FILES+=		regress.R-1.out
 ${PACKAGE}FILES+=		regress.in
 ${PACKAGE}FILES+=		regress.n1.out
 ${PACKAGE}FILES+=		regress.n2.out
-${PACKAGE}FILES+=		regress.n2147483647.out
+${PACKAGE}FILES+=		regress.nargmax.out
 ${PACKAGE}FILES+=		regress.n2P0.out
 ${PACKAGE}FILES+=		regress.n3.out
 ${PACKAGE}FILES+=		regress.normal.out

usr.bin/xargs/tests/regress.sh

@@ -1,5 +1,5 @@
 
-echo 1..21
+echo 1..23
 
 REGRESSION_START($1)
 
@@ -12,9 +12,8 @@ REGRESSION_TEST(`R', `xargs -I% -R1 echo The % % % %% % % <${SRCDIR}/regress.in'
 REGRESSION_TEST(`R-1', `xargs -I% -R-1 echo The % % % %% % % <${SRCDIR}/regress.in')
 REGRESSION_TEST(`n1', `xargs -n1 echo <${SRCDIR}/regress.in')
 REGRESSION_TEST(`n2', `xargs -n2 echo <${SRCDIR}/regress.in')
-# This test may consume a large amount of memory, making it unsuited to CI
-# environments.  Disable it for now.
-#REGRESSION_TEST(`n2147483647', `xargs -n2147483647 <${SRCDIR}/regress.in')
+argmax=$(sysctl -n kern.argmax)
+REGRESSION_TEST(`nargmax', `xargs -n$argmax <${SRCDIR}/regress.in')
 REGRESSION_TEST(`n2P0',`xargs -n2 -P0 echo <${SRCDIR}/regress.in | sort')
 REGRESSION_TEST(`n3', `xargs -n3 echo <${SRCDIR}/regress.in')
 REGRESSION_TEST(`0', `xargs -0 -n1 echo <${SRCDIR}/regress.0.in')
@@ -28,5 +27,6 @@ REGRESSION_TEST_FREEFORM(`parallel1', `echo /var/empty       /var/empty       |
 REGRESSION_TEST_FREEFORM(`parallel2', `echo /var/empty       /var/empty/nodir | xargs -n1 -P2 test -d; [ $? = 1 ]')
 REGRESSION_TEST_FREEFORM(`parallel3', `echo /var/empty/nodir /var/empty       | xargs -n1 -P2 test -d; [ $? = 1 ]')
 REGRESSION_TEST_FREEFORM(`parallel4', `echo /var/empty/nodir /var/empty/nodir | xargs -n1 -P2 test -d; [ $? = 1 ]')
+REGRESSION_TEST_FREEFORM(`ntoobig', `seq 42 | xargs -n$((argmax+1)); [ $? = 1 ]')
 
 REGRESSION_END()

usr.bin/xargs/xargs.c

@@ -166,7 +166,7 @@ main(int argc, char *argv[])
 			break;
 		case 'n':
 			nflag = 1;
-			nargs = (int)strtonum(optarg, 1, INT_MAX, &errstr);
+			nargs = (int)strtonum(optarg, 1, arg_max, &errstr);
 			if (errstr)
 				errx(1, "-%c %s: %s", ch, optarg, errstr);
 			break;