GDB dump-obj extension

A GDB-Python script that converts the C/C++ object specified by obj_name to a Python dictionary object which allows for json print out or other processing afterward

Important!!
Remeber to compile the C/C++ code with -g debug option

Tested POD, union, stl, std::string, Enum and Class with virtual inheritance

C-style strings (char[] and const char *) are treated as strings, if you are using them as buffers, you need to change the handling for these types

My test environment is Ubuntu 22.04 with GDB 12.1 and gcc 11.4.0. GDB may behave differently for different version on different OS.

usage

You need to load the script by CLI -x option, e.g., gdb -x dump_obj.py test/test1, or use source command in GDB, source dump_obj.py
Then you can use it in the same way as the print command. dump-obj {variable name}, this will print out the JSON representation of the object

Alternatively, you can create a driver_func() similar to the one in dump_obj.py to set up the debugging context
then run gdb: gdb -x dump_obj.py to automatic the process, you can also use the gdb command text file to achieve the same automation

Example

C++ code

class Global_data {};
Global_data g_data;
class MyData {
    enum Day_t {
        Mon, Tue, Wed, Thu, Fri, Sat, Sun
    };
    struct Nested_t
    {
        int nested_int = 2;
    };

    int i_data = 1;
    float f_data = 3.14;
    char* p = nullptr;
    const char* str = "const string";
    Nested_t nested;
    Day_t day_enum[2] = {Mon, Sat};
    int* i_ptr = &nested.nested_int;
    Global_data* g_ptr = &g_data;
    Nested_t* member_ptr = &nested;
};

MyDataClass obj;

This will generate the following JSON string (formatted externally)

{
  "i_data(int)": 1,
  "f_data(float)": 3.1400001,
  "p(char *)": "((nullptr))",
  "str(const char *)": "const string",
  "nested(MyData::Nested_t)": {
    "nested_int(int)": 2
  },
  "day_enum(enum MyData::Day_t [2])": [
    "MyData::Mon",
    "MyData::Sat"
  ],
  "i_ptr(int *)": "(value=2) @ 0x7fffffffdfe8",
  "g_ptr(Global_data *)": "g_data @ 0x555555558011",
  "member_ptr(MyData::Nested_t *)": "0x7fffffffdfe8"
}

Ref

https://sourceware.org/gdb/current/onlinedocs/gdb.html/Types-In-Python.html
https://sourceware.org/gdb/current/onlinedocs/gdb.html/Values-From-Inferior.html

Contact

kyle0923@qq.com