Fix a comment for ValueObject::GetValueDidChange after r231526

[ki.stfu]

Summary

Fix a comment for ValueObject::GetValueDidChange after r231526.

This fix was requested by @jingham.

[jingham]

I'm not sure what you mean by "You need to update its value before." That's not a complete sentence. I'd just leave that out.

[ki.stfu]

In D8206#137827, @jingham wrote:

I'm not sure what you mean by "You need to update its value before." That's not a complete sentence. I'd just leave that out.

I meant "You need to update its value first".

Ok, I'll prepare a new patch.

[ki.stfu]

some changes

[jingham]

That's fine.

Jim

[clayborg]

A better comment might be:

"Values that persist between stops, like local variables in a function in a specific stack frame, can say if the value has changed. A SBValue must have been previously asked to retrieve its value via GetValue(), GetSummary(), GetValueAsSigned(), GetValueAsUnsigned(), or GetLocation() before it can answer if a value has changed on subsequent stops or after expression evaluation. Any SBValue that returns NULL from SBValue::GetValue() is considered to not have a value. Aggregate values like structs, unions, classes, and arrays fall into this category. The SBValue objects for these values and will never return "true" for a call to GetValueDidChange() as the code would need to compute all child values and ask if any child values have changed in order to correctly return the result. This can be very expensive to calculate and could cause IDEs with variable views displaying many variables to incur performance problems if the variables are not expanded in the GUI. If this functionality is desired, the current SBValue API can be used to iterate across all children and ask each child SBValue if each one has changed."

include/lldb/API/SBValue.h

public:
     GetValueAsSigned(int64_t fail_value=0);
     
     uint64_t
     GetValueAsUnsigned(uint64_t fail_value=0);
 
     ValueType
     GetValueType ();
 
-    // It will be only valid starting from the second time.
+    // If you call this on a newly created ValueObject, it will always return false.
     bool
     GetValueDidChange ();
 
     const char *
     GetSummary ();
     
     const char *
     GetSummary (lldb::SBStream& stream,

include/lldb/Core/ValueObject.h

//        SetContext (ExecutionContextScope *exe_scope);
     DumpPrintableRepresentation (Stream& s,
                                  ValueObjectRepresentationStyle val_obj_display = eValueObjectRepresentationStyleSummary,
                                  lldb::Format custom_format = lldb::eFormatInvalid,
                                  PrintableRepresentationSpecialCases special = ePrintableRepresentationSpecialCasesAllow,
                                  bool do_dump_error = true);
     bool
     GetValueIsValid () const;
 
-    // It will be only valid starting from the second time.
+    // If you call this on a newly created ValueObject, it will always return false.
     bool
     GetValueDidChange ();
 
     bool
     UpdateValueIfNeeded (bool update_format = true);
     
     bool
     UpdateFormatsIfNeeded();