CODEWITHSUNDEEP
c++g++libc++ninja
herbertluo
herbertluo

Reputation: 79

What's the difference between `std::basic_string` and `std::__1::basic_string`?

ninja (version: 1.9.0) output:

mergetree_test.cpp:(.text+0x19f): undefined reference to `DB::executeQuery(std::string const&, DB::Context&, bool, DB::QueryProcessingStage::Enum, bool)'

nm -A mergetree_test.o | grep executeQuery | c++filt output:

mergetree_test.o:                 U DB::executeQuery(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, DB::Context&, bool, DB::QueryProcessingStage::Enum, bool)

But I got output from linked libaries where executeQuery defined using the same method.

libdbms.a:executeQuery.cpp.o:0000000000008750 T DB::executeQuery(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, DB::Context&, bool, DB::QueryProcessingStage::Enum, bool)

What does __1 mean ? how can I solve the problem ?

Upvotes: 3

Views: 2303

Answers (2)

Marshall Clow
Marshall Clow

Reputation: 16670

I suspect that you're attempting to combine libraries that were compiled using libc++ and libstdc++.

libc++ puts (almost) all of it's symbols into std::_1::, while libstdc++ puts it's symbols in std::

Upvotes: 5

Nikita Demodov
Nikita Demodov

Reputation: 571

You asked two questions so I'm gonna answer the main one(What is __1?):

__1 is an inline namespace located in std:

namespace std
{
    inline namespace __1
    {
        // string, ...
    }
}

The inline means that one does not have to specify that the structure/function/variable is located in that namespace, so that one can simply use std::string instead of std::__1::string.

As for why you are getting errors: We can't know without you providing us with some code.

Upvotes: 0

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