[lldb] Have lldb-server assign ports to children in platform mode

lldb/docs/use/qemu-testing.rst

@@ -172,6 +172,7 @@ forwarded for this to work.
 
 .. note::
   These options are used to create a "port map" within ``lldb-server``.
-  Unfortunately this map is not shared across all the processes it may create,
+  Unfortunately this map is not cleaned up on Windows on connection close,
   and across a few uses you may run out of valid ports. To work around this,
   restart the platform every so often, especially after running a set of tests.
+  This is tracked here: https://github.com/llvm/llvm-project/issues/90923

lldb/tools/lldb-server/lldb-platform.cpp

@@ -282,17 +282,12 @@ int main_platform(int argc, char *argv[]) {
     }
   }
 
-  do {
-    GDBRemoteCommunicationServerPlatform platform(
-        acceptor_up->GetSocketProtocol(), acceptor_up->GetSocketScheme());
-
-    if (port_offset > 0)
-      platform.SetPortOffset(port_offset);
-
-    if (!gdbserver_portmap.empty()) {
-      platform.SetPortMap(std::move(gdbserver_portmap));
-    }
+  GDBRemoteCommunicationServerPlatform platform(
+      acceptor_up->GetSocketProtocol(), acceptor_up->GetSocketScheme());
+  if (port_offset > 0)
+    platform.SetPortOffset(port_offset);
 
+  do {
     const bool children_inherit_accept_socket = true;
     Connection *conn = nullptr;
     error = acceptor_up->Accept(children_inherit_accept_socket, conn);
@@ -301,13 +296,37 @@ int main_platform(int argc, char *argv[]) {
       exit(socket_error);
     }
     printf("Connection established.\n");
+
     if (g_server) {
       // Collect child zombie processes.
 #if !defined(_WIN32)
-      while (waitpid(-1, nullptr, WNOHANG) > 0)
-        ;
+      ::pid_t waitResult;
+      while ((waitResult = waitpid(-1, nullptr, WNOHANG)) > 0) {
+        // waitResult is the child pid
+        gdbserver_portmap.FreePortForProcess(waitResult);
+      }
 #endif
-      if (fork()) {
+      // TODO: Clean up portmap for Windows when children die
+      // See https://github.com/llvm/llvm-project/issues/90923
+
+      // After collecting zombie ports, get the next available
+      GDBRemoteCommunicationServerPlatform::PortMap portmap_for_child;
+      llvm::Expected<uint16_t> available_port =
+          gdbserver_portmap.GetNextAvailablePort();
+      if (available_port)
+        portmap_for_child.AllowPort(*available_port);
+      else {
+        llvm::consumeError(available_port.takeError());
+        fprintf(stderr,
+                "no available gdbserver port for connection - dropping...\n");
+        delete conn;
+        continue;
+      }
+      platform.SetPortMap(std::move(portmap_for_child));
+
+      auto childPid = fork();
+      if (childPid) {
+        gdbserver_portmap.AssociatePortWithProcess(*available_port, childPid);
         // Parent doesn't need a connection to the lldb client
         delete conn;
 
@@ -323,7 +342,11 @@ int main_platform(int argc, char *argv[]) {
       // If not running as a server, this process will not accept
       // connections while a connection is active.
       acceptor_up.reset();
+
+      // When not running in server mode, use all available ports
+      platform.SetPortMap(std::move(gdbserver_portmap));
     }
+
     platform.SetConnection(std::unique_ptr<Connection>(conn));
 
     if (platform.IsConnected()) {