[Lldb-commits] [lldb] [lldb] Fix StdUnorderedMapSynthProvider for GCC (PR #164251)
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Mon Oct 20 06:13:02 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-lldb
Author: Sergei Druzhkov (DrSergei)
<details>
<summary>Changes</summary>
This patch adds small workaround for [issue](https://github.com/llvm/llvm-project/issues/152504). It looks like code compiled with gcc has lack of some important debug information (e.g. DW_TAG_template_type_parameter for allocator).
Example code:
```cpp
#include <unordered_map>
int main() {
std::unordered_map<int, int> map = {
{1, 2}
};
return 0;
}
```
Output from `llvm-dwarfdump` for code compiled by GCC or Clang.
GCC:
```
0x00001fcd: DW_TAG_class_type
DW_AT_name ("allocator<std::pair<int const, int> >")
DW_AT_byte_size (0x01)
DW_AT_decl_file ("/usr/include/c++/13/bits/allocator.h")
DW_AT_decl_line (130)
DW_AT_decl_column (11)
DW_AT_sibling (0x0000207c)
0x00001fda: DW_TAG_inheritance
DW_AT_type (0x00001d0a "std::__new_allocator<std::pair<int const, int> >")
DW_AT_data_member_location (0)
DW_AT_accessibility (DW_ACCESS_public)
0x00001fe0: DW_TAG_subprogram
DW_AT_external (true)
DW_AT_name ("allocator")
DW_AT_decl_file ("/usr/include/c++/13/bits/allocator.h")
DW_AT_decl_line (163)
DW_AT_decl_column (7)
DW_AT_linkage_name ("_ZNSaISt4pairIKiiEEC4Ev")
DW_AT_accessibility (DW_ACCESS_public)
DW_AT_declaration (true)
DW_AT_object_pointer (0x00001ff4)
DW_AT_sibling (0x00001ffa)
0x00001ff4: DW_TAG_formal_parameter
DW_AT_type (0x00004eb9 "std::allocator<std::pair<int const, int> > *")
DW_AT_artificial (true)
0x00001ff9: NULL
0x00001ffa: DW_TAG_subprogram
DW_AT_external (true)
DW_AT_name ("allocator")
DW_AT_decl_file ("/usr/include/c++/13/bits/allocator.h")
DW_AT_decl_line (167)
DW_AT_decl_column (7)
DW_AT_linkage_name ("_ZNSaISt4pairIKiiEEC4ERKS2_")
DW_AT_accessibility (DW_ACCESS_public)
DW_AT_declaration (true)
DW_AT_object_pointer (0x0000200e)
DW_AT_sibling (0x00002019)
0x0000200e: DW_TAG_formal_parameter
DW_AT_type (0x00004eb9 "std::allocator<std::pair<int const, int> > *")
DW_AT_artificial (true)
0x00002013: DW_TAG_formal_parameter
DW_AT_type (0x00004ec3 "const std::allocator<std::pair<int const, int> > &")
0x00002018: NULL
0x00002019: DW_TAG_subprogram
DW_AT_external (true)
DW_AT_name ("operator=")
DW_AT_decl_file ("/usr/include/c++/13/bits/allocator.h")
DW_AT_decl_line (172)
DW_AT_decl_column (18)
DW_AT_linkage_name ("_ZNSaISt4pairIKiiEEaSERKS2_")
DW_AT_type (0x00004ec8 "std::allocator<std::pair<int const, int> > &")
DW_AT_accessibility (DW_ACCESS_public)
DW_AT_declaration (true)
DW_AT_defaulted (DW_DEFAULTED_in_class)
DW_AT_object_pointer (0x00002031)
DW_AT_sibling (0x0000203c)
0x00002031: DW_TAG_formal_parameter
DW_AT_type (0x00004eb9 "std::allocator<std::pair<int const, int> > *")
DW_AT_artificial (true)
0x00002036: DW_TAG_formal_parameter
DW_AT_type (0x00004ec3 "const std::allocator<std::pair<int const, int> > &")
0x0000203b: NULL
0x0000203c: DW_TAG_subprogram
DW_AT_external (true)
DW_AT_name ("~allocator")
DW_AT_decl_file ("/usr/include/c++/13/bits/allocator.h")
DW_AT_decl_line (184)
DW_AT_decl_column (7)
DW_AT_linkage_name ("_ZNSaISt4pairIKiiEED4Ev")
DW_AT_accessibility (DW_ACCESS_public)
DW_AT_declaration (true)
DW_AT_object_pointer (0x00002050)
DW_AT_sibling (0x0000205b)
0x00002050: DW_TAG_formal_parameter
DW_AT_type (0x00004eb9 "std::allocator<std::pair<int const, int> > *")
DW_AT_artificial (true)
0x00002055: DW_TAG_formal_parameter
DW_AT_type (0x00004cab "int")
DW_AT_artificial (true)
0x0000205a: NULL
```
Clang:
```
0x00001a6e: DW_TAG_class_type
DW_AT_calling_convention (DW_CC_pass_by_reference)
DW_AT_name ("allocator<std::pair<const int, int> >")
DW_AT_byte_size (0x01)
DW_AT_decl_file ("/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/allocator.h")
DW_AT_decl_line (130)
0x00001a74: DW_TAG_template_type_parameter
DW_AT_type (0x00000dec "std::pair<const int, int>")
DW_AT_name ("_Tp")
0x00001a7a: DW_TAG_inheritance
DW_AT_type (0x00001ad5 "std::__allocator_base<std::pair<const int, int> >")
DW_AT_data_member_location (0x00)
DW_AT_accessibility (DW_ACCESS_public)
0x00001a81: DW_TAG_subprogram
DW_AT_name ("allocator")
DW_AT_decl_file ("/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/allocator.h")
DW_AT_decl_line (163)
DW_AT_declaration (true)
DW_AT_external (true)
DW_AT_accessibility (DW_ACCESS_public)
0x00001a86: DW_TAG_formal_parameter
DW_AT_type (0x00002dd1 "std::allocator<std::pair<const int, int> > *")
DW_AT_artificial (true)
0x00001a8b: NULL
0x00001a8c: DW_TAG_subprogram
DW_AT_name ("allocator")
DW_AT_decl_file ("/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/allocator.h")
DW_AT_decl_line (167)
DW_AT_declaration (true)
DW_AT_external (true)
DW_AT_accessibility (DW_ACCESS_public)
0x00001a91: DW_TAG_formal_parameter
DW_AT_type (0x00002dd1 "std::allocator<std::pair<const int, int> > *")
DW_AT_artificial (true)
0x00001a96: DW_TAG_formal_parameter
DW_AT_type (0x00002dd6 "const std::allocator<std::pair<const int, int> > &")
0x00001a9b: NULL
0x00001a9c: DW_TAG_subprogram
DW_AT_linkage_name ("_ZNSaISt4pairIKiiEEaSERKS2_")
DW_AT_name ("operator=")
DW_AT_decl_file ("/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/allocator.h")
DW_AT_decl_line (172)
DW_AT_type (0x00002de0 "std::allocator<std::pair<const int, int> > &")
DW_AT_declaration (true)
DW_AT_external (true)
DW_AT_accessibility (DW_ACCESS_public)
0x00001aa6: DW_TAG_formal_parameter
DW_AT_type (0x00002dd1 "std::allocator<std::pair<const int, int> > *")
DW_AT_artificial (true)
0x00001aab: DW_TAG_formal_parameter
DW_AT_type (0x00002dd6 "const std::allocator<std::pair<const int, int> > &")
0x00001ab0: NULL
0x00001ab1: DW_TAG_subprogram
DW_AT_name ("~allocator")
DW_AT_decl_file ("/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/allocator.h")
DW_AT_decl_line (184)
DW_AT_declaration (true)
DW_AT_external (true)
DW_AT_accessibility (DW_ACCESS_public)
0x00001ab6: DW_TAG_formal_parameter
DW_AT_type (0x00002dd1 "std::allocator<std::pair<const int, int> > *")
DW_AT_artificial (true)
0x00001abb: NULL
```
I propose to add fallback implementation based on type of `_M_h`.
---
Full diff: https://github.com/llvm/llvm-project/pull/164251.diff
1 Files Affected:
- (modified) lldb/examples/synthetic/gnu_libstdcpp.py (+5)
``````````diff
diff --git a/lldb/examples/synthetic/gnu_libstdcpp.py b/lldb/examples/synthetic/gnu_libstdcpp.py
index f42a009c21f48..54d6248185fda 100644
--- a/lldb/examples/synthetic/gnu_libstdcpp.py
+++ b/lldb/examples/synthetic/gnu_libstdcpp.py
@@ -68,6 +68,11 @@ def extract_type(self):
template_arg_num = type.GetNumberOfTemplateArguments() - 1
allocator_type = type.GetTemplateArgumentType(template_arg_num)
data_type = allocator_type.GetTemplateArgumentType(0)
+ if data_type.IsValid():
+ return data_type
+ type = self.head.GetType()
+ head_type = type.GetTypedefedType().GetTypedefedType()
+ data_type = head_type.GetTemplateArgumentType(1)
return data_type
def update(self):
``````````
</details>
https://github.com/llvm/llvm-project/pull/164251
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