[lldb/API] Fix the dangling pointer issue in SBThread::GetStopDescription

[mib]

Summary

Instead of creating a char pointer to hold the stop reason description,
the reason is stored in a std::string.

[friss]

lldb/source/API/SBThread.cpp

361–363

I don't think this is generally safe. Creating a std::string from a nullptr is undefined (and the previous test makes it look like this pointer could be null).

[JDevlieghere]

lldb/source/API/SBThread.cpp

361–363

GetStopDescription now returns a std::string, so it should be fine here?

[JDevlieghere]

lldb/source/API/SBThread.cpp

357

This looks like some "optimization" to not have to compute the strlen below if the string is known. I dont't think we need this anymore with the description being a string?

394

You could simplify this

if (!stop_desc.empty() && dst) {

[JDevlieghere]

lldb/source/API/SBThread.cpp

361–363

nvm, I didn't see the variable got assigned again

[mib]

I'll merge this with D73303

lldb/source/API/SBThread.cpp

size_t SBThread::GetStopDescription(char *dst, size_t dst_len) {
   ExecutionContext exe_ctx(m_opaque_sp.get(), lock);
 
   if (exe_ctx.HasThreadScope()) {
     Process::StopLocker stop_locker;
     if (stop_locker.TryLock(&exe_ctx.GetProcessPtr()->GetRunLock())) {
 
       StopInfoSP stop_info_sp = exe_ctx.GetThreadPtr()->GetStopInfo();
       if (stop_info_sp) {
-        const char *stop_desc =
-            exe_ctx.GetThreadPtr()->GetStopDescription().c_str();
-        if (stop_desc) {
+        std::string stop_desc = exe_ctx.GetThreadPtr()->GetStopDescription();
+        if (!stop_desc.empty()) {
           if (dst)
-            return ::snprintf(dst, dst_len, "%s", stop_desc);
+            return ::snprintf(dst, dst_len, "%s", stop_desc.c_str());
           else {
             // NULL dst passed in, return the length needed to contain the
             // description
-            return ::strlen(stop_desc) + 1; // Include the NULL byte for size
+            return stop_desc.size() + 1; // Include the NULL byte for size
           }
         } else {
           size_t stop_desc_len = 0;
           switch (stop_info_sp->GetStopReason()) {
           case eStopReasonTrace:
           case eStopReasonPlanComplete: {
             static char trace_desc[] = "step";
             stop_desc = trace_desc;
             stop_desc_len =
                 sizeof(trace_desc); // Include the NULL byte for size
           } break;
 
           case eStopReasonBreakpoint: {
             static char bp_desc[] = "breakpoint hit";
             stop_desc = bp_desc;
             stop_desc_len = sizeof(bp_desc); // Include the NULL byte for size
           } break;
 
           case eStopReasonWatchpoint: {
             static char wp_desc[] = "watchpoint hit";
             stop_desc = wp_desc;
             stop_desc_len = sizeof(wp_desc); // Include the NULL byte for size
           } break;
 
           case eStopReasonSignal: {
             stop_desc =
                 exe_ctx.GetProcessPtr()->GetUnixSignals()->GetSignalAsCString(
                     stop_info_sp->GetValue());
-            if (stop_desc == nullptr || stop_desc[0] == '\0') {
+            if (stop_desc.empty()) {
               static char signal_desc[] = "signal";
               stop_desc = signal_desc;
               stop_desc_len =
                   sizeof(signal_desc); // Include the NULL byte for size
             }
           } break;
 
           case eStopReasonException: {
if (stop_locker.TryLock(&exe_ctx.GetProcessPtr()->GetRunLock())) {
             char limbo_desc[] = "thread exiting";
             stop_desc = limbo_desc;
             stop_desc_len = sizeof(limbo_desc);
           } break;
           default:
             break;
           }
 
-          if (stop_desc && stop_desc[0]) {
+          if (!stop_desc.empty()) {
             if (dst)
-              return ::snprintf(dst, dst_len, "%s", stop_desc) +
+              return ::snprintf(dst, dst_len, "%s", stop_desc.c_str()) +
                      1; // Include the NULL byte
 
             if (stop_desc_len == 0)
-              stop_desc_len = ::strlen(stop_desc) + 1; // Include the NULL byte
+              stop_desc_len = stop_desc.size() + 1; // Include the NULL byte
 
             return stop_desc_len;
           }
         }
       }
     }
   }
   if (dst)