[Lldb-commits] [lldb] [lldb-dap] Create telemetry data only when built with telemetry. (PR #225785)

[Ebuka Ezike via lldb-commits]

https://github.com/da-viper created https://github.com/llvm/llvm-project/pull/225785

I am exploring fuzzing some parts of lldb-dap. but there is a fixed amount of memory lldb-dap can use before the fuzzing stops to catch memory leaks.
The telemetry dispatcher always creates telemetry regardless of if lldb is built with telemetry enabled.

`SBStructuredData::SetFromJSON` adds the telemetry string to the ConstString pool for every request and grows lldb-dap's memory usage rapidly.

>From ad1fcf389063694a07f49dcb88f9f64c39739f18 Mon Sep 17 00:00:00 2001
From: Ebuka Ezike <e_ezike at apple.com>
Date: Sat, 19 Sep 2026 13:04:26 +0100
Subject: [PATCH] [lldb-dap] Log telemetry only when built with telemetry.

I am exploring fuzzing some parts of lldb-dap. but there is a fixed
amount of memory lldb-dap can use before the fuzzing stops to catch
memory leaks.
The telemetry dispatcher always creates telemetry regardless of if
lldb is built with telemetry enabled.

`SBStructuredData::SetFromJSON` adds the telemetry string to the
ConstString pool for every request and grows lldb-dap's memory usage
rapidly.
---
 lldb/tools/lldb-dap/DAP.cpp     |  4 ++--
 lldb/tools/lldb-dap/LLDBUtils.h | 34 +++++++++++++++++++++------------
 2 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/lldb/tools/lldb-dap/DAP.cpp b/lldb/tools/lldb-dap/DAP.cpp
index cb87c314e46658..dda56e87b68d18 100644
--- a/lldb/tools/lldb-dap/DAP.cpp
+++ b/lldb/tools/lldb-dap/DAP.cpp
@@ -693,7 +693,7 @@ void DAP::SetTarget(const lldb::SBTarget target) { this->target = target; }
 
 bool DAP::HandleObject(const Message &M) {
   TelemetryDispatcher dispatcher(&debugger);
-  dispatcher.Set("client_name", m_client_name.str());
+  dispatcher.Set("client_name", m_client_name);
   if (const auto *req = std::get_if<Request>(&M)) {
     {
       std::lock_guard<std::mutex> guard(m_active_request_mutex);
@@ -759,7 +759,7 @@ bool DAP::HandleObject(const Message &M) {
                            }),
                        *resp->message);
       }
-      dispatcher.Set("error", message.str());
+      dispatcher.Set("error", message);
 
       (*response_handler)(llvm::createStringError(
           std::error_code(-1, std::generic_category()), message));
diff --git a/lldb/tools/lldb-dap/LLDBUtils.h b/lldb/tools/lldb-dap/LLDBUtils.h
index 30882b75fa3596..1c48c6f72d2400 100644
--- a/lldb/tools/lldb-dap/LLDBUtils.h
+++ b/lldb/tools/lldb-dap/LLDBUtils.h
@@ -23,8 +23,10 @@
 #include "llvm/Support/JSON.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Telemetry/Telemetry.h"
 #include <chrono>
 #include <string>
+#include <utility>
 
 namespace lldb_dap {
 
@@ -139,26 +141,22 @@ std::string GetSBFileSpecPath(const lldb::SBFileSpec &file_spec);
 lldb::SBLineEntry GetLineEntryForAddress(lldb::SBTarget &target,
                                          const lldb::SBAddress &address);
 
-/// Helper for sending telemetry to lldb server, if client-telemetry is enabled.
-class TelemetryDispatcher {
+namespace detail {
+
+template <bool Enabled = llvm::telemetry::Config::BuildTimeEnableTelemetry>
+class TelemetryDispatcherImpl {
 public:
-  TelemetryDispatcher(lldb::SBDebugger *debugger) {
-    m_telemetry_json = llvm::json::Object();
+  TelemetryDispatcherImpl(lldb::SBDebugger *debugger) : debugger(debugger) {
     m_telemetry_json.try_emplace(
         "start_time",
         std::chrono::steady_clock::now().time_since_epoch().count());
-    this->debugger = debugger;
-  }
-
-  void Set(std::string key, std::string value) {
-    m_telemetry_json.try_emplace(key, value);
   }
 
-  void Set(std::string key, int64_t value) {
-    m_telemetry_json.try_emplace(key, value);
+  template <typename T> void Set(llvm::StringRef key, T &&value) {
+    m_telemetry_json.try_emplace(key, std::forward<T>(value));
   }
 
-  ~TelemetryDispatcher() {
+  ~TelemetryDispatcherImpl() {
     m_telemetry_json.try_emplace(
         "end_time",
         std::chrono::steady_clock::now().time_since_epoch().count());
@@ -176,6 +174,18 @@ class TelemetryDispatcher {
   lldb::SBDebugger *debugger;
 };
 
+template <> class TelemetryDispatcherImpl<false> {
+public:
+  TelemetryDispatcherImpl(lldb::SBDebugger *) {}
+  template <typename T> void Set(llvm::StringRef, T &&) {}
+};
+
+} // namespace detail
+
+/// Helper for sending telemetry to lldb server, if built with telemetry and
+/// client-telemetry is enabled.
+using TelemetryDispatcher = detail::TelemetryDispatcherImpl<>;
+
 /// RAII utility to put the debugger temporarily  into synchronous mode.
 class ScopeSyncMode {
 public: