[PATCH 8/8] xap_helper: clamp workers to USHRT_MAX

[Eric Wong]

This allows us to avoid any integer overflow problems while
having enough room to grow for some future hardware, though it
looks like having hundreds of cores isn't ever going to make
it to typical servers nor workstations.
---
 lib/PublicInbox/xap_helper.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/PublicInbox/xap_helper.h b/lib/PublicInbox/xap_helper.h
index add2fe8c..7210c940 100644
--- a/lib/PublicInbox/xap_helper.h
+++ b/lib/PublicInbox/xap_helper.h
@@ -78,6 +78,7 @@ static FILE *orig_err = stderr;
 static int orig_err_fd = -1;
 static void *srch_tree; // tsearch + tdelete + twalk
 static pid_t *worker_pids; // nr => pid
+#define WORKER_MAX USHRT_MAX
 static unsigned long nworker, nworker_hwm;
 static int pipefds[2];
 
@@ -1063,6 +1064,10 @@ static void do_sigchld(void)
 static void do_sigttin(void)
 {
        if (!alive) return;
+       if (nworker >= WORKER_MAX) {
+               warnx("workers cannot exceed %zu", (size_t)WORKER_MAX);
+               return;
+       }
        void *p = reallocarray(worker_pids, nworker + 1, sizeof(pid_t));
        if (!p) {
                warn("reallocarray");
@@ -1117,7 +1122,7 @@ int main(int argc, char *argv[])
 #ifdef _SC_NPROCESSORS_ONLN
        long j = sysconf(_SC_NPROCESSORS_ONLN);
        if (j > 0)
-               nworker = j > UCHAR_MAX ? UCHAR_MAX : j;
+               nworker = j > WORKER_MAX ? WORKER_MAX : j;
 #endif // _SC_NPROCESSORS_ONLN
 
        // make warn/warnx/err multi-process friendly:
@@ -1130,7 +1135,7 @@ int main(int argc, char *argv[])
                switch (c) {
                case 'j':
                        nworker = strtoul(optarg, &end, 10);
-                       if (*end != 0 || nworker > USHRT_MAX)
+                       if (*end != 0 || nworker > WORKER_MAX)
                                errx(EXIT_FAILURE, "-j %s invalid", optarg);
                        break;
                case ':':