[lldb-vscode] Follow up of D99989 - store some strings more safely

[wallace]

Summary

As a follow up of https://reviews.llvm.org/D99989#inline-953343, I'm now
storing std::string instead of char *. I know it might never break as char *,
but if it does, chasing that bug might be dauting.

[JDevlieghere]

lldb/tools/lldb-vscode/lldb-vscode.cpp

2934

Have you considered an`llvm::StringMap`, it should be more performant.

[wallace]

TIL. I'll give it a try

[wallace]

lldb/tools/lldb-vscode/lldb-vscode.cpp

2934

I've been reading https://llvm.org/devmtg/2014-04/PDFs/LightningTalks/data_structure_llvm.pdf and it seems that it's not more performant speed-wise. I imagine it's more performance space-wise, but here I mostly care about time.

[clayborg]

lldb/tools/lldb-vscode/lldb-vscode.cpp

2939

This will crash if "variable.GetName()" return nullptr. We should check and only add if not nullptr

[wallace]

now checking if the strings gotten from the API are null or not

[wallace]

lldb/tools/lldb-vscode/JSONUtils.cpp

925 ↗

(On Diff #341017)

i had to change this because std::string(nullptr) throws on my machine

[shafik]

lldb/tools/lldb-vscode/JSONUtils.cpp

925 ↗

(On Diff #341017)

Yes, the std::string constructor taking a const CharT* expects a null terminated C-string.

lldb/tools/lldb-vscode/lldb-vscode.cpp

case VARREF_REGS:
       num_children = g_vsc.num_regs;
       break;
     default:
       break;
     }
     const int64_t end_idx = start_idx + ((count == 0) ? num_children : count);
 
     // We first find out which variable names are duplicated
-    llvm::DenseMap<const char *, int> variable_name_counts;
+    std::map<std::string, int> variable_name_counts;
     for (auto i = start_idx; i < end_idx; ++i) {
       lldb::SBValue variable = g_vsc.variables.GetValueAtIndex(i);
       if (!variable.IsValid())
         break;
       variable_name_counts[variable.GetName()]++;
     }
 
     // Now we construct the result with unique display variable names
     for (auto i = start_idx; i < end_idx; ++i) {
       lldb::SBValue variable = g_vsc.variables.GetValueAtIndex(i);
       const char *name = variable.GetName();
 
       if (!variable.IsValid())