GetTemplateArgumentType from std::unordered_map allocator returns "No value"

[bea231]

Hello, I'm trying to write my own variable printer for std::unordered_map for debugging GCC compiled program under LLDB (because the standard one always shows size=0). I've found an example in the repository and but it seems like its self.count is always None.

I tried to set up some debug printing in the extract_type and got the following:

def extract_type(self):
        type = self.valobj.GetType()

        template_arg_num = 4 if self.kind == "map" else 3
        allocator_type = type.GetTemplateArgumentType(template_arg_num)
        data_type = allocator_type.GetTemplateArgumentType(0)

        print("allocator_type:", allocator_type) # Debug output
        print("data_type:", data_type) # Debug output
        print("allocator_type arguments count:", allocator_type.GetNumberOfTemplateArguments()) # Debug output
        return data_type

It successfully fetches the allocator_type as:

(lldb) p someMap
allocator_type: class allocator<std::pair<char const, long unsigned int> > : public std::__new_allocator<std::pair<const char, unsigned long> > {
    template <class _Tp1> struct rebind;
    template<> struct rebind<std::__detail::_Hash_node<std::pair<const char, unsigned long>, false>> {
        typedef std::allocator<std::__detail::_Hash_node<std::pair<char const, long unsigned int>, false> > other;
    };
public:
    void allocator();
    void allocator(const std::allocator<std::pair<char const, long unsigned int> > &);
    std::allocator<std::pair<char const, long unsigned int> > &operator=(const std::allocator<std::pair<char const, long unsigned int> > &);
    ~allocator<std::pair<char const, long unsigned int> >();
}
data_type: No value
allocator_type arguments count: 0

But allocator_type.GetNumberOfTemplateArguments() always returns 0 and data_type is "No value".

Here are some details to reproduce the issue:

Code to reproduce

LLDB version

❯ lldb --version
lldb version 19.1.7

GCC version

❯ g++ --version
g++ (GCC) 13.3.0
Copyright (C) 2023 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

C++ code

#include <bits/stdc++.h>

int main() {
  std::unordered_map<char, size_t> someMap;
  someMap.emplace('a', 2);
  std::cout << someMap.size() << std::endl;
  return 0;
}

Compilation command

g++ -g -O0 main.cpp
LLDB_DEBUGSERVER_PATH=/Applications/Xcode.app/Contents/SharedFrameworks/LLDB.framework/Versions/A/Resources/debugserver lldb a.out

OS and env

MacBook Air M1, 16GB, MacOS Sequoia Version 15.6 (24G84)

[llvmbot]

@llvm/issue-subscribers-lldb

Author: Artemii Sergeev (bea231)

Hello, I'm trying to write my own variable printer for `std::unordered_map` for debugging GCC compiled program under LLDB (because the standard one always shows `size=0`). I've found an [example](https://github.com/llvm/llvm-project/commit/fcd288b52aa708e061ad633c8efa1183a7e6b926#diff-7edac4d10a9ab393c8232bb22b656cc8608e973b508a24e349a249dd06df4846R16) in the repository and but it seems like its `self.count` is always `None`.

I tried to set up some debug printing in the extract_type and got the following:

def extract_type(self):
        type = self.valobj.GetType()

        template_arg_num = 4 if self.kind == "map" else 3
        allocator_type = type.GetTemplateArgumentType(template_arg_num)
        data_type = allocator_type.GetTemplateArgumentType(0)

        print("allocator_type:", allocator_type) # Debug output
        print("data_type:", data_type) # Debug output
        print("allocator_type arguments count:", allocator_type.GetNumberOfTemplateArguments()) # Debug output
        return data_type

It successfully fetches the allocator_type as:

(lldb) p someMap
allocator_type: class allocator<std::pair<char const, long unsigned int> > : public std::__new_allocator<std::pair<const char, unsigned long> > {
    template <class _Tp1> struct rebind;
    template<> struct rebind<std::__detail::_Hash_node<std::pair<const char, unsigned long>, false>> {
        typedef std::allocator<std::__detail::_Hash_node<std::pair<char const, long unsigned int>, false> > other;
    };
public:
    void allocator();
    void allocator(const std::allocator<std::pair<char const, long unsigned int> > &);
    std::allocator<std::pair<char const, long unsigned int> > &operator=(const std::allocator<std::pair<char const, long unsigned int> > &);
    ~allocator<std::pair<char const, long unsigned int> >();
}
data_type: No value
allocator_type arguments count: 0

But allocator_type.GetNumberOfTemplateArguments() always returns 0 and data_type is "No value".

Here are some details to reproduce the issue:

<details>
<summary>Code to reproduce</summary>

LLDB version

❯ lldb --version
lldb version 19.1.7

GCC version

❯ g++ --version
g++ (GCC) 13.3.0
Copyright (C) 2023 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

C++ code

#include <bits/stdc++.h>

int main() {
  std::unordered_map<char, size_t> someMap;
  someMap.emplace('a', 2);
  std::cout << someMap.size() << std::endl;
  return 0;
}

Compilation command

g++ -g -O0 main.cpp
LLDB_DEBUGSERVER_PATH=/Applications/Xcode.app/Contents/SharedFrameworks/LLDB.framework/Versions/A/Resources/debugserver lldb a.out

OS and env

MacBook Air M1, 16GB, MacOS Sequoia Version 15.6 (24G84)

</details>