How to Resolve `std::__cxx11::string` and `std::string` Incompatibility Issues When Linking Libraries?

Converting __cxx11::string to std::string: A Guide to Handling Incompatible Libraries

Encountering incompatibility between the std::__cxx11::string type and the regular std::string can be a frustrating issue. When trying to interface with libraries that may not be configured for C 11, the need arises to convert between these types. However, simply attempting to cast a std::__cxx11::string to a std::string using (string) doesn't suffice.

This issue can often manifest as linker errors, such as:

undefined reference to `H5::CompType::insertMember(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&amp;, unsigned long, H5::DataType const&amp;) const'

Understanding the Ursache:

One possible cause for this incompatibility lies in the use of GCC 5. GCC 5 introduced dual ABIs for the C standard library, where code compiled with one ABI cannot be linked with code compiled with the other. If a third-party library was compiled with an older ABI while your code uses the newer ABI, linking issues can arise.

The Solution:

To resolve this issue, define the macro _GLIBCXX_USE_CXX11_ABI to 0 before including any standard library headers. This forces GCC to use the older ABI, ensuring compatibility with the third-party library.

#define _GLIBCXX_USE_CXX11_ABI 0
#include <iostream>
#include <string>

With this macro defined, the linker should be able to successfully resolve the symbols and the conversion from std::__cxx11::string to std::string should proceed without errors.

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