gdb 没有在线程中加载漂亮的打印机？

Question

I am currently trying to setup a VSCode project (the Godot sources for anyone interested), with compilation and debugging, however I can't get the pretty printers of GDB (version 8.1.1) to work.

In a regular application (a simple helloworld.cpp), if I compile, and debug, then get the pretty printer info, I get the foolowing:

    (gdb) info pretty-printer 
global pretty-printers:
  builtin
    mpx_bound128
  objfile /usr/lib/x86_64-linux-gnu/libstdc++.so.6 pretty-printers:
  libstdc++-v6 [disabled]
    __gnu_cxx::_Slist_iterator
    __gnu_cxx::__8::_Slist_iterator
    __gnu_cxx::__8::__normal_iterator
    __gnu_cxx::__8::slist
    __gnu_cxx::__normal_iterator
    __gnu_cxx::slist
    __gnu_debug::_Safe_iterator
    std::_Deque_const_iterator
    std::_Deque_iterator
    std::_Fwd_list_const_iterator
    std::_Fwd_list_iterator
    std::_List_const_iterator
    std::_List_iterator
    std::_Node_handle
    std::_Rb_tree_const_iterator
    std::_Rb_tree_iterator
    std::__8::_Deque_const_iterator
    std::__8::_Deque_iterator
    std::__8::_Fwd_list_const_iterator
    std::__8::_Fwd_list_iterator
    std::__8::_List_const_iterator
    std::__8::_List_iterator
    std::__8::_Node_handle
    std::__8::_Rb_tree_const_iterator
    std::__8::_Rb_tree_iterator
    std::__8::__cxx11::__cxx1998::list
    std::__8::__cxx11::basic_string
    (...)

However, in my other project, when I launch the debugger and try to get info on the pretty printers, I get the following:

(gdb) info pretty-printer 
global pretty-printers:
  builtin
    mpx_bound128
  objfile /lib/x86_64-linux-gnu/libpthread.so.0 pretty-printers:
  glibc-pthread-locks
    pthread_cond_t
    pthread_condattr_t
    pthread_mutex_t
    pthread_mutexattr_t
    pthread_rwlock_t
    pthread_rwlockattr_t

And nothing more. If I put a breakpoint in the program and get data, it won't get pretty printed, eg:

$2 = {static npos = 18446744073709551615, _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, _M_p = 0xc9115d0 "salut mec ça va ?"}, _M_string_length = 18, {
    _M_local_buf = "\022\000\000\000\000\000\000\000\370\245\377\377\377\177\000", _M_allocated_capacity = 18}}

At the beginning of the debugging of my nonworking example, I get the following message:

[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Which hints me that the pretty print is not working (compared to my working example) because of the use of threads ?

To ensure that gdb uses the pretty printer, I have created a ~/.gdbinit file with the following content:

python
import sys
sys.path.insert(0, '/usr/share/gcc-8/python')
from libstdcxx.v6.printers import register_libstdcxx_printers
end

Which doesn't seem to have any effect.

Answer 1

However, in my other project, when I launch the debugger and try to get info on the pretty printers, I get the following:

This is most likely happening because your other project did not link libstdc++.so.6 -- possibly because you used -static-libstdc++ .

To ensure that gdb uses the pretty printer, I have created

Your file imports the register_libstdcxx_printers function, but doesn't call it. To actually instantiate all the libstdc++ printers, add a call:

python
import sys
sys.path.insert(0, '/usr/share/gcc-8/python')
from libstdcxx.v6.printers import register_libstdcxx_printers

register_libstdcxx_printers(None)
end