fix select exception fdset clearing

qkernel/src/syscalls/sys_poll.rs

@@ -205,7 +205,7 @@ pub fn DoSelect(
             if (events & SELECT_EXCEPT_EVENTS) != 0 {
                 bitSetCount += 1;
             } else {
-                w[i] &= !m;
+                e[i] &= !m;
             }
         }
     }

test/c/makefile

@@ -1,11 +1,13 @@
-all: std server client server_conn client_conn unixcli unixsrv socketpair stat dev fork signal futex multithread epoll mkdir fifo timerfd eventfd seek gettimeofday server_benchmark client_benchmark epoll_client epoll_server multithread_client multithread_server multithread_pp_client multithread_pp_server poll udpcli udpsrv udpclidual udpsrvdual
+all: std server client server_conn client_conn unixcli unixsrv socketpair stat dev fork signal futex multithread epoll mkdir fifo timerfd eventfd seek gettimeofday server_benchmark client_benchmark epoll_client epoll_server multithread_client multithread_server multithread_pp_client multithread_pp_server poll select_except_connect udpcli udpsrv udpclidual udpsrvdual
 
 std: std.c
 	gcc -o std std.c
 dnstest: dnstest.c
 	gcc -o dnstest dnstest.c
 poll: poll.c
 	gcc -o poll poll.c
+select_except_connect: select_except_connect.c
+	gcc -Wall -Wextra -o select_except_connect select_except_connect.c
 server: server.c
 	gcc -o server server.c
 client: client.c
@@ -79,4 +81,4 @@ udpclidual: udpclidual.c
 udpsrvdual: udpsrvdual.c
 	gcc -o udpsrvdual udpsrvdual.c
 clean:
-	rm std server client unixcli unixsrv socketpair stat dev fork signal futex multithread epoll mkdir fifo timerfd eventfd seek gettimeofday
+	rm -f std server client select_except_connect unixcli unixsrv socketpair stat dev fork signal futex multithread epoll mkdir fifo timerfd eventfd seek gettimeofday

test/c/select_except_connect.c

@@ -0,0 +1,141 @@
+// Copyright (c) 2026 Quark Container Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <netinet/in.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/select.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static void fail(const char *msg)
+{
+    perror(msg);
+    exit(1);
+}
+
+int main(void)
+{
+    int listener = socket(AF_INET, SOCK_STREAM, 0);
+    if (listener < 0) {
+        fail("socket(listener)");
+    }
+
+    int one = 1;
+    if (setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one)) < 0) {
+        fail("setsockopt(SO_REUSEADDR)");
+    }
+
+    struct sockaddr_in addr;
+    memset(&addr, 0, sizeof(addr));
+    addr.sin_family = AF_INET;
+    addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+    addr.sin_port = 0;
+
+    if (bind(listener, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
+        fail("bind(listener)");
+    }
+    if (listen(listener, 1) < 0) {
+        fail("listen(listener)");
+    }
+
+    socklen_t addr_len = sizeof(addr);
+    if (getsockname(listener, (struct sockaddr *)&addr, &addr_len) < 0) {
+        fail("getsockname(listener)");
+    }
+
+    pid_t child = fork();
+    if (child < 0) {
+        fail("fork");
+    }
+    if (child == 0) {
+        int accepted = accept(listener, NULL, NULL);
+        if (accepted < 0) {
+            fail("accept");
+        }
+        char byte;
+        (void)read(accepted, &byte, sizeof(byte));
+        close(accepted);
+        close(listener);
+        return 0;
+    }
+
+    int client = socket(AF_INET, SOCK_STREAM, 0);
+    if (client < 0) {
+        fail("socket(client)");
+    }
+    int flags = fcntl(client, F_GETFL, 0);
+    if (flags < 0 || fcntl(client, F_SETFL, flags | O_NONBLOCK) < 0) {
+        fail("fcntl(O_NONBLOCK)");
+    }
+
+    int rc = connect(client, (struct sockaddr *)&addr, sizeof(addr));
+    if (rc < 0 && errno != EINPROGRESS) {
+        fail("connect(client)");
+    }
+
+    fd_set readfds;
+    fd_set writefds;
+    fd_set exceptfds;
+    FD_ZERO(&readfds);
+    FD_ZERO(&writefds);
+    FD_ZERO(&exceptfds);
+    FD_SET(client, &readfds);
+    FD_SET(client, &writefds);
+    FD_SET(client, &exceptfds);
+
+    struct timeval timeout;
+    timeout.tv_sec = 5;
+    timeout.tv_usec = 0;
+    rc = select(client + 1, &readfds, &writefds, &exceptfds, &timeout);
+    if (rc < 0) {
+        fail("select");
+    }
+    if (rc == 0) {
+        fprintf(stderr, "select timed out\n");
+        return 1;
+    }
+
+    int err = 0;
+    socklen_t err_len = sizeof(err);
+    if (getsockopt(client, SOL_SOCKET, SO_ERROR, &err, &err_len) < 0) {
+        fail("getsockopt(SO_ERROR)");
+    }
+
+    printf("select rc=%d read=%d write=%d except=%d so_error=%d\n",
+           rc,
+           FD_ISSET(client, &readfds) != 0,
+           FD_ISSET(client, &writefds) != 0,
+           FD_ISSET(client, &exceptfds) != 0,
+           err);
+
+    if (err != 0) {
+        fprintf(stderr, "SO_ERROR=%d (%s)\n", err, strerror(err));
+        return 1;
+    }
+    if (!FD_ISSET(client, &writefds)) {
+        fprintf(stderr, "client socket was not in writefds\n");
+        return 1;
+    }
+    if (FD_ISSET(client, &exceptfds)) {
+        fprintf(stderr, "client socket was incorrectly left in exceptfds\n");
+        return 1;
+    }
+
+    (void)write(client, "x", 1);
+    close(client);
+    close(listener);
+
+    int status = 0;
+    if (waitpid(child, &status, 0) < 0) {
+        fail("waitpid");
+    }
+    return status == 0 ? 0 : 1;
+}