Invert sense of getpgrp test.

AC_FUNC_GETPGRP tests if getpgrp(0) works, which it does if it's not
declared.  Instead, test if the zero-arg version we want to use works.

configure.ac

@@ -1736,7 +1736,6 @@ AC_CHECK_FUNCS([ \
 	getpeereid \
 	getpeerucred \
 	getpgid \
-	getpgrp \
 	_getpty \
 	getrlimit \
 	getsid \
@@ -2413,7 +2412,16 @@ static void sighandler(int sig) { _exit(1); }
 	)
 fi
 
-AC_FUNC_GETPGRP
+AC_CHECK_FUNCS([getpgrp],[
+	AC_MSG_CHECKING([if getpgrp accepts zero args])
+	AC_COMPILE_IFELSE(
+		[AC_LANG_PROGRAM([[$ac_includes_default]], [[ getpgrp(); ]])],
+		[ AC_MSG_RESULT([yes])
+		  AC_DEFINE([GETPGRP_VOID], [1], [getpgrp takes zero args])],
+		[ AC_MSG_RESULT([no])
+		  AC_DEFINE([GETPGRP_VOID], [0], [getpgrp takes one arg])]
+	)
+])
 
 # Search for OpenSSL
 saved_CPPFLAGS="$CPPFLAGS"

openbsd-compat/bsd-misc.c

@@ -238,7 +238,7 @@ isblank(int c)
 pid_t
 getpgid(pid_t pid)
 {
-#if defined(HAVE_GETPGRP) && !defined(GETPGRP_VOID)
+#if defined(HAVE_GETPGRP) && !defined(GETPGRP_VOID) && GETPGRP_VOID == 0
 	return getpgrp(pid);
 #elif defined(HAVE_GETPGRP)
 	if (pid == 0)