1. 旧的 std :: string 与C ++ 11，因为该标准禁止写时复制实现。没有办法创建一个兼容的 std :: string ，而不会破坏ABI，所以他们这样做，返回到不兼容版本的ABI兼容性。




2. 确认您程式中的所有翻译单元都使用相同的值 _GLIBCXX_USE_CXX11_ABI ，你应该没问题。如果你把它们混合在翻译单位，你一定会有问题。如果在不将 string 彼此沟通的不同翻译单元中具有不同的define值，则您可能 >

https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html

I ran into crashing/valgrind issues with using std::string on GCC 5. The above link hints that there is a change in the ABI starting GCC 5.x. The new default ABI for libstd++ is C++11/14... which is not compatible with the older ABI. There is a way to select the older ABI using a define.

I am trying to understand what is the difference between the ABIs and haven't found details. I'd like help understanding:

1. What kind of issues with std::string need to be fixed to be compatible with the new ABI? Are they copy-on-write related?
2. Will those changes break it for older ABI?
3. Any tips in getting _GLIBCXX_USE_CXX11_ABI to work?

More details on the issue I ran into (https://github.com/YasserAsmi/jvar/issues/21) The project worked fine in GCC 4.8 and Clang. With GCC, the same code refuses to run:

x_misc(33112,0x7fff728c2000) malloc: *** error for object 0x7fd639c034cc:    pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Abort trap: 6

And here is a partial Valgrind output: ==33027== Invalid read of size 1 ==33027== at 0x1006F78BA: _platform_memmove$VARIANT$Nehalem (in /usr/lib/system/libsystem_platform.dylib) ==33027== by 0x100009388: jvar::Variant::toStringabi:cxx11 const (in bin/ex_misc) ==33027== by 0x1000023A7: bugreport() (in bin/ex_misc) ==33027== by 0x1000133B8: main (in bin/ex_misc)

The project uses std::string and has some custom memory management. It is doing some non-typical but valid operations using placement new constructors etc. I am trying to understand better what kind of code is effected by the API and how to fix it--a place to start.

1. The old std::string was not compliant with C++11 because that standard prohibits a copy-on-write implementation. There was no way to create a compliant std::string without breaking ABI, so they did so with a way to return to the non-compliant version for ABI compatibility.

2. Yes.

3. Make sure all the translation units in your program use the same value of _GLIBCXX_USE_CXX11_ABI and you should be fine. If you mix them up across translation units you will definitely have problems. You might be ok if you have different values of the define in different translation units that don't communicate strings to each other.