Where is the definition of some member functions (ex. __gnu_debug::_Safe_iterator_base::_M_detach())?

Where is the definition of some member functions (ex. __gnu_debug::_Safe_iterator_base::_M_detach())?

[Tan, Qiye]

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Hi all,

I'm new in C++ who have an interest in the implementation of C++ STL.
Recently, I tried to implement my own vector template. However, when I
implemented my own iterator, I found that I had no idea how to
detect whether it is dereferencable. Therefore, I began to explore the
libstdc++, but I found that for some member functions, I can only find the
declaration but no definition. For example, the 'bool
__gnu_debug::_Safe_iterator_base::_M_singular(  ) const', 'void
__gnu_debug::_Safe_iterator_base::_M_detach(  )', etc. They are declared in
'libstdc++-v3/include/debug/safe_base.h'. I can guess that '_M_singular'
may just check if '_M_sequence' is NULL, but I still want to find their
definition. Can someone help me? Thank you so much.

Best,
Qiye Tan

Re: Where is the definition of some member functions (ex. __gnu_debug::_Safe_iterator_base::_M_detach())?

[Arsen Arsenović]

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Evening,

"Tan, Qiye via Libstdc++" <libstdc++@gcc.gnu.org> writes:

> I'm new in C++ who have an interest in the implementation of C++ STL.
> Recently, I tried to implement my own vector template. However, when I
> implemented my own iterator, I found that I had no idea how to
> detect whether it is dereferencable. Therefore, I began to explore the
> libstdc++, but I found that for some member functions, I can only find the
> declaration but no definition. For example, the 'bool
> __gnu_debug::_Safe_iterator_base::_M_singular(  ) const', 'void
> __gnu_debug::_Safe_iterator_base::_M_detach(  )', etc. They are declared in
> 'libstdc++-v3/include/debug/safe_base.h'. I can guess that '_M_singular'
> may just check if '_M_sequence' is NULL, but I still want to find their
> definition. Can someone help me? Thank you so much.

_M_singular() and _M_detach() are implemented in src/c++11/debug.cc.  A
complete iterator implementation technically doesn't need either, these
are used for debugging purposes in libstdc++, see also
https://gcc.gnu.org/onlinedocs/gcc-12.2.0/libstdc++/api/a05206.html

Do keep in mind that the __gnu_debug namespace is only used in case that
_GLIBCXX_DEBUG is set, see
https://gcc.gnu.org/onlinedocs/gcc-12.2.0/libstdc++/manual/manual/debug_mode.html

Hope that helps, have a great night!
-- 
Arsen Arsenović

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Re: Where is the definition of some member functions (ex. __gnu_debug::_Safe_iterator_base::_M_detach())?

[François Dumont]

On 20/11/22 20:45, Tan, Qiye via Libstdc++ wrote:
> Hi all,
>
> I'm new in C++ who have an interest in the implementation of C++ STL.
> Recently, I tried to implement my own vector template.
Good exercice !
>   However, when I
> implemented my own iterator, I found that I had no idea how to
> detect whether it is dereferencable. Therefore, I began to explore the
> libstdc++, but I found that for some member functions, I can only find the
> declaration but no definition. For example, the 'bool
> __gnu_debug::_Safe_iterator_base::_M_singular(  ) const', 'void
> __gnu_debug::_Safe_iterator_base::_M_detach(  )', etc. They are declared in
> 'libstdc++-v3/include/debug/safe_base.h'. I can guess that '_M_singular'
> may just check if '_M_sequence' is NULL, but I still want to find their
> definition. Can someone help me? Thank you so much.

This is in the .so, all exports are done from the src folder.

For _GLIBCXX_DEBUG mode all implementation is in src/c++11/debug.cc.

François

Re: Where is the definition of some member functions (ex. __gnu_debug::_Safe_iterator_base::_M_detach())?

[Jonathan Wakely]

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On Sun, 20 Nov 2022, 19:45 Tan, Qiye via Libstdc++, <libstdc++@gcc.gnu.org>
wrote:

> Hi all,
>
> I'm new in C++ who have an interest in the implementation of C++ STL.
> Recently, I tried to implement my own vector template. However, when I
> implemented my own iterator, I found that I had no idea how to
> detect whether it is dereferencable. Therefore, I began to explore the
> libstdc++, but I found that for some member functions, I can only find the
> declaration but no definition. For example, the 'bool
> __gnu_debug::_Safe_iterator_base::_M_singular(  ) const', 'void
> __gnu_debug::_Safe_iterator_base::_M_detach(  )', etc. They are declared in
> 'libstdc++-v3/include/debug/safe_base.h'. I can guess that '_M_singular'
> may just check if '_M_sequence' is NULL, but I still want to find their
> definition. Can someone help me? Thank you so much.
>

François and Arsen gave the answer already, but for future reference you
could clone the git repository and use 'git grep _M_singular' to find that.



> Best,
> Qiye Tan
>