[lldb] Change return type of UnixSignals::GetShortName

[bulbazord]

Summary

The short names of each signal name and alias only exist as ConstStrings
in this one scenario. For example, GetShortName("SIGHUP") will just give
you "HUP". There's not a good reason the string "HUP" needs to be in the
ConstString StringPool, and that's true for just about every signal
name.

[mib]

Don't you need to update the callers as well ? Otherwise LGTM.

[bulbazord]

In D152582#4410002, @mib wrote:

Don't you need to update the callers as well ? Otherwise LGTM.

ConstString can be implicitly converted to StringRef which is what's happening here. There are only 2 call sites, both pass in a ConstString.

[JDevlieghere]

Cool

lldb/include/lldb/Target/UnixSignals.h

public:
   int32_t GetFirstSignalNumber() const;
 
   int32_t GetNextSignalNumber(int32_t current_signal) const;
 
   int32_t GetNumSignals() const;
 
   int32_t GetSignalAtIndex(int32_t index) const;
 
-  ConstString GetShortName(ConstString name) const;
-
   // We assume that the elements of this object are constant once it is
   // constructed, since a process should never need to add or remove symbols as
   // it runs.  So don't call these functions anywhere but the constructor of
   // your subclass of UnixSignals or in your Process Plugin's GetUnixSignals
   // method before you return the UnixSignal object.
 
   void AddSignal(int signo, const char *name, bool default_suppress,
                  bool default_stop, bool default_notify,
struct Signal {
 
     Signal(const char *name, bool default_suppress, bool default_stop,
            bool default_notify, const char *description, const char *alias);
 
     ~Signal() = default;
     void Reset(bool reset_stop, bool reset_notify, bool reset_suppress);
   };
 
+  llvm::StringRef GetShortName(llvm::StringRef name) const;
+
   virtual void Reset();
 
   typedef std::map<int32_t, Signal> collection;
 
   collection m_signals;
 
   // This version gets incremented every time something is changing in this
   // class, including when we call AddSignal from the constructor. So after the

lldb/source/Target/UnixSignals.cpp

UnixSignals::GetSignalDescription(int32_t signo, std::optional<int32_t> code,
 
   return str;
 }
 
 bool UnixSignals::SignalIsValid(int32_t signo) const {
   return m_signals.find(signo) != m_signals.end();
 }
 
-ConstString UnixSignals::GetShortName(ConstString name) const {
-  if (name)
-    return ConstString(name.GetStringRef().substr(3)); // Remove "SIG" from name
-  return name;
+llvm::StringRef UnixSignals::GetShortName(llvm::StringRef name) const {
+  return name.substr(3); // Remove "SIG" from name
 }
 
 int32_t UnixSignals::GetSignalNumberFromName(const char *name) const {
   ConstString const_name(name);
 
   collection::const_iterator pos, end = m_signals.end();
   for (pos = m_signals.begin(); pos != end; pos++) {
     if ((const_name == pos->second.m_name) ||