[lldb] Guarantee the lifetimes of all strings returned from SBAPI

LLDB should guarantee that the strings returned by SBAPI methods
live forever. I went through every method that returns a string and made
sure that it was added to the ConstString StringPool before returning if
it wasn't obvious that it was already doing so.
I've also updated the docs to document this behavior.

Differential Revision: https://reviews.llvm.org/D150804

1 files changed, 14 insertions, 16 deletions

diff --git a/lldb/source/API/SBThread.cpp b/lldb/source/API/SBThread.cpp
index 35cc45d..bdd9311 100644
--- a/lldb/source/API/SBThread.cpp
+++ b/lldb/source/API/SBThread.cpp
@@ -394,35 +394,33 @@ uint32_t SBThread::GetIndexID() const {
 const char *SBThread::GetName() const {
   LLDB_INSTRUMENT_VA(this);
 
-  const char *name = nullptr;
   std::unique_lock<std::recursive_mutex> lock;
   ExecutionContext exe_ctx(m_opaque_sp.get(), lock);
 
-  if (exe_ctx.HasThreadScope()) {
-    Process::StopLocker stop_locker;
-    if (stop_locker.TryLock(&exe_ctx.GetProcessPtr()->GetRunLock())) {
-      name = exe_ctx.GetThreadPtr()->GetName();
-    }
-  }
+  if (!exe_ctx.HasThreadScope())
+    return nullptr;
+
+  Process::StopLocker stop_locker;
+  if (stop_locker.TryLock(&exe_ctx.GetProcessPtr()->GetRunLock()))
+    return ConstString(exe_ctx.GetThreadPtr()->GetName()).GetCString();
 
-  return name;
+  return nullptr;
 }
 
 const char *SBThread::GetQueueName() const {
   LLDB_INSTRUMENT_VA(this);
 
-  const char *name = nullptr;
   std::unique_lock<std::recursive_mutex> lock;
   ExecutionContext exe_ctx(m_opaque_sp.get(), lock);
 
-  if (exe_ctx.HasThreadScope()) {
-    Process::StopLocker stop_locker;
-    if (stop_locker.TryLock(&exe_ctx.GetProcessPtr()->GetRunLock())) {
-      name = exe_ctx.GetThreadPtr()->GetQueueName();
-    }
-  }
+  if (!exe_ctx.HasThreadScope())
+    return nullptr;
+
+  Process::StopLocker stop_locker;
+  if (stop_locker.TryLock(&exe_ctx.GetProcessPtr()->GetRunLock()))
+    return ConstString(exe_ctx.GetThreadPtr()->GetQueueName()).GetCString();
 
-  return name;
+  return nullptr;
 }
 
 lldb::queue_id_t SBThread::GetQueueID() const {