[lldb] Make variant formatter work with libstdc++-14 (#97568)

In this version the internal data member has grown an additional
template parameter (bool), which was throwing the summary provider off.

This patch uses the type of the entire variant object. This is part of
the API/ABI, so it should be more stable, but it means we have to
explicitly strip typedefs and references to get to the interesting bits,
which is why I've extended the test case with examples of those.

3 files changed, 21 insertions, 11 deletions

diff --git a/lldb/examples/synthetic/gnu_libstdcpp.py b/lldb/examples/synthetic/gnu_libstdcpp.py
index f778065..d98495b 100644
--- a/lldb/examples/synthetic/gnu_libstdcpp.py
+++ b/lldb/examples/synthetic/gnu_libstdcpp.py
@@ -914,12 +914,15 @@ def VariantSummaryProvider(valobj, dict):
     if index == npos_value:
         return " No Value"
 
+    # Strip references and typedefs.
+    variant_type = raw_obj.GetType().GetCanonicalType().GetDereferencedType()
+    template_arg_count = variant_type.GetNumberOfTemplateArguments()
+
     # Invalid index can happen when the variant is not initialized yet.
-    template_arg_count = data_obj.GetType().GetNumberOfTemplateArguments()
     if index >= template_arg_count:
         return " <Invalid>"
 
-    active_type = data_obj.GetType().GetTemplateArgumentType(index)
+    active_type = variant_type.GetTemplateArgumentType(index)
     return f" Active Type = {active_type.GetDisplayTypeName()} "
 
 
diff --git a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/TestDataFormatterLibStdcxxVariant.py b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/TestDataFormatterLibStdcxxVariant.py
index ba16418..ea4a53f 100644
--- a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/TestDataFormatterLibStdcxxVariant.py
+++ b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/TestDataFormatterLibStdcxxVariant.py
@@ -21,15 +21,17 @@ class LibStdcxxVariantDataFormatterTestCase(TestBase):
 
         lldbutil.continue_to_breakpoint(self.process, bkpt)
 
-        self.expect(
-            "frame variable v1",
-            substrs=["v1 =  Active Type = int  {", "Value = 12", "}"],
-        )
-
-        self.expect(
-            "frame variable v1_ref",
-            substrs=["v1_ref =  Active Type = int : {", "Value = 12", "}"],
-        )
+        for name in ["v1", "v1_typedef"]:
+            self.expect(
+                "frame variable " + name,
+                substrs=[name + " =  Active Type = int  {", "Value = 12", "}"],
+            )
+
+        for name in ["v1_ref", "v1_typedef_ref"]:
+            self.expect(
+                "frame variable " + name,
+                substrs=[name + " =  Active Type = int : {", "Value = 12", "}"],
+            )
 
         self.expect(
             "frame variable v_v1",
diff --git a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/main.cpp b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/main.cpp
index 545318f..36e0f74 100644
--- a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/main.cpp
+++ b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/main.cpp
@@ -14,6 +14,10 @@ int main() {
 
   std::variant<int, double, char> v1;
   std::variant<int, double, char> &v1_ref = v1;
+  using V1_typedef = std::variant<int, double, char>;
+  V1_typedef v1_typedef;
+  V1_typedef &v1_typedef_ref = v1_typedef;
+
   std::variant<int, double, char> v2;
   std::variant<int, double, char> v3;
   std::variant<std::variant<int, double, char>> v_v1;
@@ -43,6 +47,7 @@ int main() {
       v_many_types_no_value;
 
   v1 = 12; // v contains int
+  v1_typedef = v1;
   v_v1 = v1;
   int i = std::get<int>(v1);
   printf("%d\n", i); // break here