[lldb][test] TestDataFormatterLibcxxStringSimulator.py: add new padding layout

[Michael137]

Depends on #108362 and #108343.

Adds new layout for #105865.

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Michael Buch (Michael137)

Changes

Depends on #108362 and #108343.

Adds new layout for #105865.

---

Full diff: https://github.com/llvm/llvm-project/pull/108375.diff

2 Files Affected:

• (modified) lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/TestDataFormatterLibcxxStringSimulator.py (+4-1)
• (modified) lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/main.cpp (+33-10)

diff --git a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/TestDataFormatterLibcxxStringSimulator.py b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/TestDataFormatterLibcxxStringSimulator.py
index 3e5c493692c4f0..dd9f5de22c9057 100644
--- a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/TestDataFormatterLibcxxStringSimulator.py
+++ b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/TestDataFormatterLibcxxStringSimulator.py
@@ -22,9 +22,12 @@ 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):
+    for r in range(6):
         name = "test_r%d" % r
         defines = ["REVISION=%d" % r]
         if v:
diff --git a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/main.cpp b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/main.cpp
index 7beeb9c39de49e..5cf3a85007fb64 100644
--- a/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/main.cpp
+++ b/lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/main.cpp
@@ -20,7 +20,11 @@
 // Pre-D128285 layout.
 #define PACKED_ANON_STRUCT
 #endif
-// REVISION == 4: current layout
+#if REVISION <= 4
+// Pre-TODO layout.
+#define UB_PADDING
+#endif
+// REVISION == 5: current layout
 
 #ifdef PACKED_ANON_STRUCT
 #define BEGIN_PACKED_ANON_STRUCT struct __attribute__((packed)) {
@@ -34,6 +38,7 @@
 namespace std {
 namespace __lldb {
 
+#ifdef UB_PADDING
 #if defined(ALTERNATE_LAYOUT) && defined(SUBCLASS_PADDING)
 template <class _CharT, size_t = sizeof(_CharT)> struct __padding {
   unsigned char __xx[sizeof(_CharT) - 1];
@@ -41,6 +46,13 @@ template <class _CharT, size_t = sizeof(_CharT)> struct __padding {
 
 template <class _CharT> struct __padding<_CharT, 1> {};
 #endif
+#else // !UB_PADDING
+template <size_t _PaddingSize> struct __padding {
+  char __padding_[_PaddingSize];
+};
+
+template <> struct __padding<0> {};
+#endif
 
 template <class _CharT, class _Traits, class _Allocator> class basic_string {
 public:
@@ -71,19 +83,25 @@ template <class _CharT, class _Traits, class _Allocator> class basic_string {
 
   struct __short {
     value_type __data_[__min_cap];
-#ifdef BITMASKS
 #ifdef SUBCLASS_PADDING
     struct : __padding<value_type> {
       unsigned char __size_;
     };
-#else
+#else // !SUBCLASS_PADDING
+
+#ifdef UB_PADDING
     unsigned char __padding[sizeof(value_type) - 1];
-    unsigned char __size_;
+#else
+    [[no_unique_address]] __padding<sizeof(value_type) - 1> __padding_;
 #endif
+
+#ifdef BITMASKS
+    unsigned char __size_;
 #else // !BITMASKS
     unsigned char __size_ : 7;
     unsigned char __is_long_ : 1;
-#endif
+#endif // BITMASKS
+#endif // SUBCLASS_PADDING
   };
 
 #ifdef BITMASKS
@@ -128,21 +146,26 @@ template <class _CharT, class _Traits, class _Allocator> class basic_string {
     union {
 #ifdef BITMASKS
       unsigned char __size_;
-#else
+#else  // !BITMASKS
       struct {
         unsigned char __is_long_ : 1;
         unsigned char __size_ : 7;
       };
-#endif
+#endif // BITMASKS
       value_type __lx;
     };
-#else
+#else  // !SHORT_UNION
     BEGIN_PACKED_ANON_STRUCT
     unsigned char __is_long_ : 1;
     unsigned char __size_ : 7;
     END_PACKED_ANON_STRUCT
-    char __padding_[sizeof(value_type) - 1];
-#endif
+#ifdef UB_PADDING
+    unsigned char __padding[sizeof(value_type) - 1];
+#else  // !UB_PADDING
+    [[no_unique_address]] __padding<sizeof(value_type) - 1> __padding_;
+#endif // UB_PADDING
+
+#endif // SHORT_UNION
     value_type __data_[__min_cap];
   };
 

[labath]

Was that (the zero sized array) really UB? Or just a compiler extension?

[Michael137]

Good point! I'll rename it to NON_STANDARD_PADDING

[Michael137]

(this libc++-side change was relanded in: #108867)

[Michael137]

Broke the lldb-aarch64-windows2921 bot