"libc++abi" C++ Standard Library Support
libc++abi is a new implementation of low level support for a standard C++ library.
All of the code in libc++abi is dual licensed under the MIT license and the UIUC License (a BSD-like license).
Features and Goals
- Correctness as defined by the C++11 standard.
- Provide a portable sublayer to ease the porting of libc++
- On Mac OS X, be ABI compatible with the existing low-level support.
Platform Support
libc++abi is known to work on the following platforms, using clang.
- Darwin
Current Status
libc++abi is complete. Here is a list of functionality.
Get it and get involved!
For building libc++abi, please see the libc++ documentation on building the runtimes.
For getting involved with libc++abi, please see the libc++ documentation on 百度 百度 百度.
Frequently asked questions
Q: Why are the destructors for the standard exception classes defined in libc++abi? They're just empty, can't they be defined inline?
A: The destructors for them live in libc++abi because they are "key" functions.
The Itanium ABI describes a "key" function as the first virtual declared.
And wherever the key function is defined, that is where the type_info gets defined.
And in libc++ types are the same type if and only if they have the same type_info
(as in there must be only one type info per type in the entire application).
And on OS X, libstdc++ and libc++ share these exception types.
So to be able to throw in one dylib and catch in another (a std::exception for example),
there must be only one std::exception type_info in the entire app.
That typeinfo gets laid down beside ~exception() in libc++abi (for both libstdc++ and libc++).
--Howard Hinnant