[lldb][DataFormatter] Surface CalculateNumChildren errors in std::vector summary (#135944)

lldb/packages/Python/lldbsuite/test/make/libcxx-simulators-common/compressed_pair.h

@@ -7,7 +7,13 @@
 namespace std {
 namespace __lldb {
 
-// Post-c88580c layout
+#if __has_cpp_attribute(msvc::no_unique_address)
+#define _LLDB_NO_UNIQUE_ADDRESS [[msvc::no_unique_address]]
+#elif __has_cpp_attribute(no_unique_address)
+#define _LLDB_NO_UNIQUE_ADDRESS [[__no_unique_address__]]
+#endif
+
+#if COMPRESSED_PAIR_REV == 0 // Post-c88580c layout
 struct __value_init_tag {};
 struct __default_init_tag {};
 
@@ -52,6 +58,54 @@ class __compressed_pair : private __compressed_pair_elem<_T1, 0>,
 
   _T1 &first() { return static_cast<_Base1 &>(*this).__get(); }
 };
+#elif COMPRESSED_PAIR_REV == 1
+// From libc++ datasizeof.h
+template <class _Tp> struct _FirstPaddingByte {
+  _LLDB_NO_UNIQUE_ADDRESS _Tp __v_;
+  char __first_padding_byte_;
+};
+
+template <class _Tp>
+inline const size_t __datasizeof_v =
+    __builtin_offsetof(_FirstPaddingByte<_Tp>, __first_padding_byte_);
+
+template <class _Tp>
+struct __lldb_is_final : public integral_constant<bool, __is_final(_Tp)> {};
+
+template <class _ToPad> class __compressed_pair_padding {
+  char __padding_[((is_empty<_ToPad>::value &&
+                    !__lldb_is_final<_ToPad>::value) ||
+                   is_reference<_ToPad>::value)
+                      ? 0
+                      : sizeof(_ToPad) - __datasizeof_v<_ToPad>];
+};
+
+#define _LLDB_COMPRESSED_PAIR(T1, Initializer1, T2, Initializer2)              \
+  [[__gnu__::__aligned__(                                                      \
+      alignof(T2))]] _LLDB_NO_UNIQUE_ADDRESS T1 Initializer1;                  \
+  _LLDB_NO_UNIQUE_ADDRESS __compressed_pair_padding<T1> __padding1_;           \
+  _LLDB_NO_UNIQUE_ADDRESS T2 Initializer2;                                     \
+  _LLDB_NO_UNIQUE_ADDRESS __compressed_pair_padding<T2> __padding2_;
+
+#define _LLDB_COMPRESSED_TRIPLE(T1, Initializer1, T2, Initializer2, T3,        \
+                                Initializer3)                                  \
+  [[using __gnu__: __aligned__(alignof(T2)),                                   \
+    __aligned__(alignof(T3))]] _LLDB_NO_UNIQUE_ADDRESS T1 Initializer1;        \
+  _LLDB_NO_UNIQUE_ADDRESS __compressed_pair_padding<T1> __padding1_;           \
+  _LLDB_NO_UNIQUE_ADDRESS T2 Initializer2;                                     \
+  _LLDB_NO_UNIQUE_ADDRESS __compressed_pair_padding<T2> __padding2_;           \
+  _LLDB_NO_UNIQUE_ADDRESS T3 Initializer3;                                     \
+  _LLDB_NO_UNIQUE_ADDRESS __compressed_pair_padding<T3> __padding3_;
+#elif COMPRESSED_PAIR_REV == 2
+#define _LLDB_COMPRESSED_PAIR(T1, Name1, T2, Name2)                            \
+  _LLDB_NO_UNIQUE_ADDRESS T1 Name1;                                            \
+  _LLDB_NO_UNIQUE_ADDRESS T2 Name2
+
+#define _LLDB_COMPRESSED_TRIPLE(T1, Name1, T2, Name2, T3, Name3)               \
+  _LLDB_NO_UNIQUE_ADDRESS T1 Name1;                                            \
+  _LLDB_NO_UNIQUE_ADDRESS T2 Name2;                                            \
+  _LLDB_NO_UNIQUE_ADDRESS T3 Name3
+#endif
 } // namespace __lldb
 } // namespace std
 

lldb/source/Plugins/Language/CPlusPlus/LibCxxVector.cpp

@@ -87,19 +87,30 @@ lldb_private::formatters::LibcxxStdVectorSyntheticFrontEnd::
 llvm::Expected<uint32_t> lldb_private::formatters::
     LibcxxStdVectorSyntheticFrontEnd::CalculateNumChildren() {
   if (!m_start || !m_finish)
-    return 0;
+    return llvm::createStringError(
+        "Failed to determine start/end of vector data.");
+
   uint64_t start_val = m_start->GetValueAsUnsigned(0);
   uint64_t finish_val = m_finish->GetValueAsUnsigned(0);
 
-  if (start_val == 0 || finish_val == 0)
+  // A default-initialized empty vector.
+  if (start_val == 0 && finish_val == 0)
     return 0;
 
-  if (start_val >= finish_val)
-    return 0;
+  if (start_val == 0)
+    return llvm::createStringError("Invalid value for start of vector.");
+
+  if (finish_val == 0)
+    return llvm::createStringError("Invalid value for end of vector.");
+
+  if (start_val > finish_val)
+    return llvm::createStringError(
+        "Start of vector data begins after end pointer.");
 
   size_t num_children = (finish_val - start_val);
   if (num_children % m_element_size)
-    return 0;
+    return llvm::createStringError("Size not multiple of element size.");
+
   return num_children / m_element_size;
 }
 

lldb/source/ValueObject/ValueObject.cpp

@@ -1589,10 +1589,16 @@ bool ValueObject::DumpPrintableRepresentation(
       str = GetLocationAsCString();
       break;
 
-    case eValueObjectRepresentationStyleChildrenCount:
-      strm.Printf("%" PRIu64 "", (uint64_t)GetNumChildrenIgnoringErrors());
-      str = strm.GetString();
+    case eValueObjectRepresentationStyleChildrenCount: {
+      if (auto err = GetNumChildren()) {
+        strm.Printf("%" PRIu32, *err);
+        str = strm.GetString();
+      } else {
+        strm << "error: " << toString(err.takeError());
+        str = strm.GetString();
+      }
       break;
+    }
 
     case eValueObjectRepresentationStyleType:
       str = GetTypeName().GetStringRef();

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/invalid-vector/Makefile

@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+override CXXFLAGS_EXTRAS += -std=c++20
+include Makefile.rules

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/invalid-vector/TestDataFormatterLibcxxInvalidVectorSimulator.py

@@ -0,0 +1,39 @@
+"""
+Test we can understand various layouts of the libc++'s std::string
+"""
+
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+import functools
+
+
+class LibcxxInvalidVectorDataFormatterSimulatorTestCase(TestBase):
+    NO_DEBUG_INFO_TESTCASE = True
+
+    def test(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "return 0", lldb.SBFileSpec("main.cpp"))
+
+        self.expect(
+            "frame variable v1",
+            substrs=["size=error: Invalid value for end of vector."],
+        )
+        self.expect(
+            "frame variable v2",
+            substrs=["size=error: Invalid value for start of vector."],
+        )
+        self.expect(
+            "frame variable v3",
+            substrs=["size=error: Start of vector data begins after end pointer."],
+        )
+        self.expect(
+            "frame variable v4",
+            substrs=["size=error: Failed to determine start/end of vector data."],
+        )
+        self.expect(
+            "frame variable v5",
+            substrs=["size=error: Size not multiple of element size."],
+        )

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/invalid-vector/main.cpp

@@ -0,0 +1,37 @@
+#define COMPRESSED_PAIR_REV 2
+#include <libcxx-simulators-common/compressed_pair.h>
+
+namespace std {
+inline namespace __1 {
+template <typename T> struct vector {
+  T *__begin_;
+  T *__end_;
+  _LLDB_COMPRESSED_PAIR(T *, __cap_ = nullptr, void *, __alloc_);
+};
+} // namespace __1
+
+inline namespace __2 {
+template <typename T> struct vector {};
+} // namespace __2
+
+inline namespace __3 {
+template <typename T> struct vector {
+  T *__begin_;
+  T *__end_;
+  _LLDB_COMPRESSED_PAIR(short *, __cap_ = nullptr, void *, __alloc_);
+};
+} // namespace __3
+} // namespace std
+
+int main() {
+  int arr[] = {1, 2, 3};
+  std::__1::vector<int> v1{.__begin_ = arr, .__end_ = nullptr};
+  std::__1::vector<int> v2{.__begin_ = nullptr, .__end_ = arr};
+  std::__1::vector<int> v3{.__begin_ = &arr[2], .__end_ = arr};
+  std::__2::vector<int> v4;
+
+  char carr[] = {'a'};
+  std::__3::vector<char> v5{.__begin_ = carr, .__end_ = carr + 1};
+
+  return 0;
+}

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/TestDataFormatterLibcxxStringSimulator.py

@@ -13,6 +13,8 @@
 class LibcxxStringDataFormatterSimulatorTestCase(TestBase):
     NO_DEBUG_INFO_TESTCASE = True
 
+    @skipIfDarwin
+    @skipIfWindows
     def _run_test(self, defines):
         cxxflags_extras = " ".join(["-D%s" % d for d in defines])
         self.build(dictionary=dict(CXXFLAGS_EXTRAS=cxxflags_extras))
@@ -22,15 +24,19 @@ def _run_test(self, defines):
         self.expect_var_path("shortstring", summary='"short"')
         self.expect_var_path("longstring", summary='"I am a very long string"')
 
+        self.expect_expr("shortstring", result_summary='"short"')
+        self.expect_expr("longstring", result_summary='"I am a very long string"')
+
 
 for v in [None, "ALTERNATE_LAYOUT"]:
-    for r in range(5):
-        name = "test_r%d" % r
-        defines = ["REVISION=%d" % r]
-        if v:
-            name += "_" + v
-            defines += [v]
-        f = functools.partialmethod(
-            LibcxxStringDataFormatterSimulatorTestCase._run_test, defines
-        )
-        setattr(LibcxxStringDataFormatterSimulatorTestCase, name, f)
+    for r in range(6):
+        for c in range(3):
+            name = "test_r%d_c%d" % (r, c)
+            defines = ["REVISION=%d" % r, "COMPRESSED_PAIR_REV=%d" % c]
+            if v:
+                name += "_" + v
+                defines += [v]
+            f = functools.partialmethod(
+                LibcxxStringDataFormatterSimulatorTestCase._run_test, defines
+            )
+            setattr(LibcxxStringDataFormatterSimulatorTestCase, name, f)