[Lldb-commits] [lldb] [lldb] Fixed the error `unable to launch a GDB server` in API tests (PR #98833)

[Dmitry Vasilyev via lldb-commits]

https://github.com/slydiman created https://github.com/llvm/llvm-project/pull/98833

TestPlatformLaunchGDBServer.py runs ldb-server w/o parameters `--min-gdbserver-port`, `--max-gdbserver-port` or `--gdbserver-port`. So `gdbserver_portmap` is empty and `gdbserver_portmap.GetNextAvailablePort()` will return 0. Do not pass 0 to `portmap_for_child` in this case. Added few asserts in `GDBRemoteCommunicationServerPlatform::PortMap` to avoid such issue in the future. 

This patch fixes #97537.

It seems StartDebugserverProcess() ignores the port anyway and parameters `--min-gdbserver-port`, `--max-gdbserver-port` and `--gdbserver-port` are useless at all, but it is out of scope of this patch.

>From e061a85a54e3493a2ba4be90612fd66252f06ba2 Mon Sep 17 00:00:00 2001
From: Dmitry Vasilyev <dvassiliev at accesssoftek.com>
Date: Sun, 14 Jul 2024 23:36:46 +0400
Subject: [PATCH] [lldb] Fixed the error `unable to launch a GDB server` in API
 tests

TestPlatformLaunchGDBServer.py runs ldb-server w/o --min-gdbserver-port, --max-gdbserver-port or --gdbserver-port, so gdbserver_portmap is empty and gdbserver_portmap.GetNextAvailablePort() will return 0. Do not pass 0 to portmap_for_child in this case. Added few asserts in GDBRemoteCommunicationServerPlatform::PortMap to avoid this in the future.
This patch fixes #97537.

It seems StartDebugserverProcess() ignores the port anyway and parameters --min-gdbserver-port, --max-gdbserver-port and --gdbserver-port are useless at all, but it is out of scope of this patch.
---
 .../GDBRemoteCommunicationServerPlatform.cpp           |  2 ++
 lldb/tools/lldb-server/lldb-platform.cpp               | 10 ++++++----
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerPlatform.cpp b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerPlatform.cpp
index 5285ec1d3db4e..65f1cc12ba307 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerPlatform.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerPlatform.cpp
@@ -46,11 +46,13 @@ using namespace lldb_private;
 
 GDBRemoteCommunicationServerPlatform::PortMap::PortMap(uint16_t min_port,
                                                        uint16_t max_port) {
+  assert(min_port);
   for (; min_port < max_port; ++min_port)
     m_port_map[min_port] = LLDB_INVALID_PROCESS_ID;
 }
 
 void GDBRemoteCommunicationServerPlatform::PortMap::AllowPort(uint16_t port) {
+  assert(port);
   // Do not modify existing mappings
   m_port_map.insert({port, LLDB_INVALID_PROCESS_ID});
 }
diff --git a/lldb/tools/lldb-server/lldb-platform.cpp b/lldb/tools/lldb-server/lldb-platform.cpp
index cfd0a3797d810..7148a1d2a3094 100644
--- a/lldb/tools/lldb-server/lldb-platform.cpp
+++ b/lldb/tools/lldb-server/lldb-platform.cpp
@@ -313,9 +313,11 @@ int main_platform(int argc, char *argv[]) {
       GDBRemoteCommunicationServerPlatform::PortMap portmap_for_child;
       llvm::Expected<uint16_t> available_port =
           gdbserver_portmap.GetNextAvailablePort();
-      if (available_port)
-        portmap_for_child.AllowPort(*available_port);
-      else {
+      if (available_port) {
+        // GetNextAvailablePort() may return 0 if gdbserver_portmap is empty.
+        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");
@@ -352,7 +354,7 @@ int main_platform(int argc, char *argv[]) {
     if (platform.IsConnected()) {
       if (inferior_arguments.GetArgumentCount() > 0) {
         lldb::pid_t pid = LLDB_INVALID_PROCESS_ID;
-        std::optional<uint16_t> port = 0;
+        std::optional<uint16_t> port;
         std::string socket_name;
         Status error = platform.LaunchGDBServer(inferior_arguments,
                                                 "", // hostname