Remove leftover blocking assertion in TCP (#785)

From review of #782

Author: alexcrichton

libc-bottom-half/sources/tcp.c

@@ -169,7 +169,6 @@ static int tcp_read_eof(void *data) {
   tcp_socket_state_connected_t *state = &tcp->state.connected;
 
   if (state->receive_result) {
-    assert(tcp->blocking);
     sockets_result_void_error_code_t result;
     __wasilibc_future_block_on(sockets_future_result_void_error_code_read(
                                    state->receive_result, &result),

test/CMakeLists.txt

@@ -415,6 +415,7 @@ if (NOT (WASI STREQUAL "p1"))
   add_wasilibc_test(getaddrinfo.c NETWORK)
   add_wasilibc_test(sockets-nonblocking.c NETWORK)
   add_wasilibc_test(sockets-nonblocking-udp-no-connection.c NETWORK)
+  add_wasilibc_test(sockets-eof-delayed.c NETWORK)
 
   # Define executables for server/client tests, and they're paired together in
   # various combinations below for various tests.

test/src/sockets-eof-delayed.c

@@ -0,0 +1,70 @@
+#include "test.h"
+#include <arpa/inet.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <netdb.h>
+#include <netinet/in.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#define TEST(c)                                                                \
+  do {                                                                         \
+    errno = 0;                                                                 \
+    if (!(c))                                                                  \
+      t_error("%s failed (errno = %d)\n", #c, errno);                          \
+  } while (0)
+
+int main() {
+  char buf[10];
+  int listener_fd = socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK, 0);
+
+  // Setup a listener bound to port 0 to have the OS assign us one.
+  struct sockaddr_in server_address;
+  socklen_t server_address_len = sizeof(server_address);
+  server_address.sin_family = AF_INET;
+  server_address.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+  server_address.sin_port = 0;
+  TEST(bind(listener_fd, (struct sockaddr *)&server_address,
+            sizeof(server_address)) != -1);
+  TEST(getsockname(listener_fd, (struct sockaddr *)&server_address,
+                   &server_address_len) != -1);
+  TEST(listen(listener_fd, 1) != -1);
+
+  // Connect a client to our server
+  int client_fd = socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK, 0);
+  TEST(client_fd != -1);
+  TEST(connect(client_fd, (struct sockaddr *)&server_address,
+               server_address_len) != -1 ||
+       errno == EINPROGRESS);
+
+  // Wait for the client to be writable, signaling the connection is there.
+  struct pollfd client, listener;
+  client.fd = client_fd;
+  client.events = POLLWRNORM;
+  TEST(poll(&client, 1, -1) == 1);
+
+  // Various ways of seeing that this isn't at EOF yet.
+  TEST(read(client_fd, buf, sizeof(buf)) == -1 && errno == EWOULDBLOCK);
+  client.events = POLLRDNORM;
+  TEST(poll(&client, 1, 0) == 0);
+  TEST(read(client_fd, buf, sizeof(buf)) == -1 && errno == EWOULDBLOCK);
+
+  // Accept the socket on the listener, then immediately close it.
+  int server_fd;
+  listener.fd = listener_fd;
+  listener.events = POLLRDNORM;
+  TEST(poll(&listener, 1, -1) == 1);
+  TEST((server_fd = accept(listener_fd, NULL, NULL)) != -1);
+  TEST(close(server_fd) != -1);
+
+  // Test to make sure that the client is now at EOF.
+  TEST(poll(&client, 1, -1) == 1);
+  TEST(read(client_fd, buf, sizeof(buf)) == 0);
+  TEST(read(client_fd, buf, sizeof(buf)) == 0);
+
+  return t_status;
+}