stdio is currently limited to file descriptors not greater than

{SHRT_MAX}, so {STREAM_MAX} should be no greater than that.  (This
does not exactly meet the letter of POSIX but comes reasonably close
to it in spirit.)

MFC after:	14 days

1 files changed, 19 insertions, 1 deletions

diff --git a/lib/libc/gen/sysconf.c b/lib/libc/gen/sysconf.c
index 8ea61af..3c342ee 100644
--- a/lib/libc/gen/sysconf.c
+++ b/lib/libc/gen/sysconf.c
@@ -100,7 +100,6 @@ sysconf(name)
 		mib[1] = KERN_NGROUPS;
 		break;
 	case _SC_OPEN_MAX:
-	case _SC_STREAM_MAX:	/* assume fds run out before memory does */
 		if (getrlimit(RLIMIT_NOFILE, &rl) != 0)
 			return (-1);
 		if (rl.rlim_cur == RLIM_INFINITY)
@@ -110,6 +109,25 @@ sysconf(name)
 			return (-1);
 		}
 		return ((long)rl.rlim_cur);
+	case _SC_STREAM_MAX:
+		if (getrlimit(RLIMIT_NOFILE, &rl) != 0)
+			return (-1);
+		if (rl.rlim_cur == RLIM_INFINITY)
+			return (-1);
+		if (rl.rlim_cur > LONG_MAX) {
+			errno = EOVERFLOW;
+			return (-1);
+		}
+		/*
+		 * struct __sFILE currently has a limitation that
+		 * file descriptors must fit in a signed short.
+		 * This doesn't precisely capture the letter of POSIX
+		 * but approximates the spirit.
+		 */
+		if (rl.rlim_cur > SHRT_MAX)
+			return (SHRT_MAX);
+
+		return ((long)rl.rlim_cur);
 	case _SC_JOB_CONTROL:
 		return (_POSIX_JOB_CONTROL);
 	case _SC_SAVED_IDS: