fix: race condition in accept_loop, auto-detect valgrind

src/server/server.c

@@ -117,6 +117,7 @@ static volatile sig_atomic_t g_server_cleanup_requested = 0;
 
 static void cleanup(int sig) {
   (void)sig;
+  server_request_shutdown();
   g_server_cleanup_requested = 1;
 }
 

src/shared/transport_tcp.c

@@ -12,6 +12,15 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
+/* Flag set by server_request_shutdown() to request graceful shutdown
+   of the accept loop. Accessed only from transport_tcp.c so it won't
+   cause linker errors when this file is compiled into client/test targets. */
+static volatile sig_atomic_t g_tcp_cleanup_requested = 0;
+
+void server_request_shutdown(void) {
+  g_tcp_cleanup_requested = 1;
+}
+
 Server* server_create(int port) {
   Server* server = (Server*)malloc(sizeof(Server));
   if (server == NULL) {
@@ -70,7 +79,7 @@ static void accept_loop(Server* server, void (*child_fn)(int, void*), void* chil
     return;
   }
   signal(SIGCHLD, SIG_IGN);
-  while (1) {
+  while (!g_tcp_cleanup_requested) {
     struct sockaddr_in client_addr;
     socklen_t client_len = sizeof(client_addr);
     int fd = accept(server->file_descriptor, (struct sockaddr*)&client_addr, &client_len);

src/shared/transport_tcp.h

@@ -26,6 +26,7 @@ bool server_listen(Server* server, void (*handler)(int file_descriptor));
 void server_accept_loop(Server* server, void (*child_fn)(int, void*), void* child_ctx,
                         const char* log_fmt);
 void server_delete(Server** server);
+void server_request_shutdown(void);
 Client* client_create();
 bool client_connect(Client* client, char* host, int port);
 void client_disconnect(Client* client);