Make pretty-printing GDB's LazyString work

Qt Creator failed to properly display GDB's LazyString.

The problem was that GDB's 'PlainDumper::__call__' passed a 'gdb.Type',
while 'DumperBase::putCharArrayHelper' called methods that are only
defined for the custom and more abstract 'Type' type defined in 'dumper.py'.

As described at [1], GDB's 'LazyString.type' "holds the type that is
represented by the lazy string’s type. For a lazy string this is a pointer
or array type. To resolve this to the lazy string’s character type,
use the type’s target method."

In addition, 'gdb.Type' does not have a 'size()' method, just a 'sizeof'
member, s. [2].

Since all other uses of 'DumperBase::putCharArrayHelper' are passed
a "proper" type, extract the code common to the GDB case and all others
into a separate method and directly call this one for the GDB LazyString
case.

[1] https://sourceware.org/gdb/onlinedocs/gdb/Lazy-Strings-In-Python.html#Lazy-Strings-In-Python
[2] https://sourceware.org/gdb/onlinedocs/gdb/Types-In-Python.html#Types-In-Python

Task-number: QTCREATORBUG-20939
Change-Id: I16608668c9403b6d8e509dab17eb1788586f453e
Reviewed-by: hjk <hjk@qt.io>

share/qtcreator/debugger/dumper.py

@@ -703,10 +703,8 @@ class DumperBase:
         elided, shown = self.computeLimit(size, limit)
         return elided, self.readMemory(data, shown)
 
-    def putCharArrayHelper(self, data, size, charType,
+    def putCharArrayValue(self, data, size, charSize,
-                           displayFormat = AutomaticFormat,
+                          displayFormat = AutomaticFormat):
-                           makeExpandable = True):
-        charSize = charType.size()
         bytelen = size * charSize
         elided, shown = self.computeLimit(bytelen, self.displayStringLimit)
         mem = self.readMemory(data, shown)
@@ -729,6 +727,12 @@ class DumperBase:
             elided, shown = self.computeLimit(bytelen, 100000)
             self.putDisplay(encodingType + ':separate', self.readMemory(data, shown))
 
+    def putCharArrayHelper(self, data, size, charType,
+                           displayFormat = AutomaticFormat,
+                           makeExpandable = True):
+        charSize = charType.size()
+        self.putCharArrayValue(data, size, charSize, displayFormat = displayFormat)
+
         if makeExpandable:
             self.putNumChild(size)
             if self.isExpanded():

share/qtcreator/debugger/gdbbridge.py

@@ -145,7 +145,8 @@ class PlainDumper:
         elif sys.version_info[0] <= 2 and isinstance(val, unicode):
             d.putValue(val)
         else: # Assuming LazyString
-            d.putCharArrayHelper(val.address, val.length, val.type)
+            d.putCharArrayValue(val.address, val.length,
+                                val.type.target().sizeof)
 
         d.putNumChild(len(children))
         if d.isExpanded():