[lldb] Reduce max-children-count default to readable size (#139826)

Change the default from 256 to 24. The argument is that 256 is too large to be scanned
by eye, and too large to print in a terminal which can be only 40-50 lines in height.

When all children must be shown, `frame variable` and `expression` both support the `-A`
(`--show-all-children`) flag.

rdar://145327522

Author: kastiglione

lldb/source/Target/TargetProperties.td

@@ -96,7 +96,7 @@ let Definition = "target" in {
     DefaultUnsignedValue<6>,
     Desc<"The maximum number of zeroes to insert when displaying a very small float before falling back to scientific notation.">;
   def MaxChildrenCount: Property<"max-children-count", "UInt64">,
-    DefaultUnsignedValue<256>,
+    DefaultUnsignedValue<24>,
     Desc<"Maximum number of children to expand in any level of depth.">;
   def MaxChildrenDepth: Property<"max-children-depth", "UInt64">,
     DefaultUnsignedValue<0xFFFFFFFF>,

lldb/test/API/functionalities/data-formatter/data-formatter-advanced/TestDataFormatterAdv.py

@@ -39,7 +39,7 @@ def test_with_run_command(self):
         def cleanup():
             self.runCmd("type format clear", check=False)
             self.runCmd("type summary clear", check=False)
-            self.runCmd("settings set target.max-children-count 256", check=False)
+            self.runCmd("settings set target.max-children-count 24", check=False)
 
         # Execute the cleanup function during test case tear down.
         self.addTearDownHook(cleanup)

lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/forward_list/TestDataFormatterGenericForwardList.py

@@ -50,7 +50,7 @@ def do_test(self, stdlib_type):
         self.expect(
             "settings show target.max-children-count",
             matching=True,
-            substrs=["target.max-children-count (unsigned) = 256"],
+            substrs=["target.max-children-count (unsigned) = 24"],
         )
 
         self.expect(
@@ -73,7 +73,7 @@ def do_test(self, stdlib_type):
         self.expect(
             "frame variable thousand_elts",
             matching=True,
-            substrs=["size=256", "[0]", "[1]", "[2]", "..."],
+            substrs=["size=24", "[0]", "[1]", "[2]", "..."],
         )
 
     def do_test_ptr_and_ref(self, stdlib_type):

lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/list/TestDataFormatterGenericList.py

@@ -50,7 +50,6 @@ def cleanup():
             self.runCmd("type summary clear", check=False)
             self.runCmd("type filter clear", check=False)
             self.runCmd("type synth clear", check=False)
-            self.runCmd("settings set target.max-children-count 256", check=False)
 
         # Execute the cleanup function during test case tear down.
         self.addTearDownHook(cleanup)

lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/multimap/TestDataFormatterGenericMultiMap.py

@@ -65,7 +65,6 @@ def cleanup():
             self.runCmd("type summary clear", check=False)
             self.runCmd("type filter clear", check=False)
             self.runCmd("type synth clear", check=False)
-            self.runCmd("settings set target.max-children-count 256", check=False)
 
         # Execute the cleanup function during test case tear down.
         self.addTearDownHook(cleanup)

lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/multiset/TestDataFormatterGenericMultiSet.py

@@ -51,7 +51,6 @@ def cleanup():
             self.runCmd("type summary clear", check=False)
             self.runCmd("type filter clear", check=False)
             self.runCmd("type synth clear", check=False)
-            self.runCmd("settings set target.max-children-count 256", check=False)
 
         # Execute the cleanup function during test case tear down.
         self.addTearDownHook(cleanup)

lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/set/TestDataFormatterGenericSet.py

@@ -51,7 +51,6 @@ def cleanup():
             self.runCmd("type summary clear", check=False)
             self.runCmd("type filter clear", check=False)
             self.runCmd("type synth clear", check=False)
-            self.runCmd("settings set target.max-children-count 256", check=False)
 
         # Execute the cleanup function during test case tear down.
         self.addTearDownHook(cleanup)

lldb/test/API/functionalities/data-formatter/data-formatter-stl/generic/unordered/TestDataFormatterGenericUnordered.py

@@ -33,7 +33,6 @@ def cleanup():
             self.runCmd("type summary clear", check=False)
             self.runCmd("type filter clear", check=False)
             self.runCmd("type synth clear", check=False)
-            self.runCmd("settings set target.max-children-count 256", check=False)
             self.runCmd("settings set auto-one-line-summaries true", check=False)
 
         # Execute the cleanup function during test case tear down.

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/iterator/TestDataFormatterLibccIterator.py

@@ -43,7 +43,6 @@ def cleanup():
             self.runCmd("type summary clear", check=False)
             self.runCmd("type filter clear", check=False)
             self.runCmd("type synth clear", check=False)
-            self.runCmd("settings set target.max-children-count 256", check=False)
 
         # Execute the cleanup function during test case tear down.
         self.addTearDownHook(cleanup)

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx/map/TestDataFormatterLibccMap.py

@@ -50,7 +50,6 @@ def cleanup():
             self.runCmd("type summary clear", check=False)
             self.runCmd("type filter clear", check=False)
             self.runCmd("type synth clear", check=False)
-            self.runCmd("settings set target.max-children-count 256", check=False)
 
         # Execute the cleanup function during test case tear down.
         self.addTearDownHook(cleanup)