[lldb][test] TestDataFormatterLibcxxStringSimulator.py: fix padding for current layout

[Michael137]

IIUC, the history of std::string's __short structure in the alternate ABI layout (as recorded by the simulator test) looks as follows:

• First layout ( SUBCLASS_PADDING is defined):

     struct __short                                          
     {                                                       
         value_type __data_[__min_cap];                      
        struct                                              
            : __padding<value_type>                         
        {                                                   
            unsigned char __size_;                          
        };
     };                                      

• Then:

     struct __short                                         
     {                                                      
        value_type __data_[__min_cap];                                                               
        unsigned char __padding[sizeof(value_type) - 1];   
        unsigned char __size_;                             
     };

• Then, post-BITMASKS:

     struct __short                                         
     {                                                      
        value_type __data_[__min_cap];                                                               
        unsigned char __padding[sizeof(value_type) - 1];   
        unsigned char __size_ : 7;
        unsigned char __is_long_ : 1;                             
     };

Which is the one that's on top-of-tree.

But for REVISION > 1, BITMASKS is never set, so for those tests we lose the __padding member.

This patch fixes this by splitting out the SUBCLASS_PADDING out of the ifdef.

Drive-by:

• Also run expression evaluator on the string to provide is with some extra coverage.

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Michael Buch (Michael137)

Changes

IIUC, the history of std::string's __short structure in the alternate ABI layout (as recorded by the simulator test) looks as follows:

• First layout ( SUBCLASS_PADDING is defined):

     struct __short                                          
     {                                                       
         value_type __data_[__min_cap];                      
        struct                                              
            : __padding<value_type>                         
        {                                                   
            unsigned char __size_;                          
        };
     };                                      

• Then:

     struct __short                                         
     {                                                      
        value_type __data_[__min_cap];                                                               
        unsigned char __padding[sizeof(value_type) - 1];   
        unsigned char __size_;                             
     };

• Then, post-BITMASKS:

     struct __short                                         
     {                                                      
        value_type __data_[__min_cap];                                                               
        unsigned char __padding[sizeof(value_type) - 1];   
        unsigned char __size_ : 7;
        unsigned char __is_long_ : 1;                             
     };

Which is the one that's on top-of-tree.

But for REVISION > 2, BITMASKS is never set, so for those tests we lose the __padding member.

This patch fixes this by

Drive-by:

• Also run expression evaluator on the string to provide is with some extra coverage.

---

Full diff: https://github.com/llvm/llvm-project/pull/108362.diff

2 Files Affected:

• (modified) lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/TestDataFormatterLibcxxStringSimulator.py (+3)
• (modified) lldb/test/API/functionalities/data-formatter/data-formatter-stl/libcxx-simulators/string/main.cpp (+3-3)

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..98d2c7320003e4 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
@@ -22,6 +22,9 @@ 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):
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..74baeba6ec879b 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
@@ -71,15 +71,15 @@ 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
+
     unsigned char __padding[sizeof(value_type) - 1];
+#ifdef BITMASKS
     unsigned char __size_;
-#endif
 #else // !BITMASKS
     unsigned char __size_ : 7;
     unsigned char __is_long_ : 1;