g++默认包含哪些库？库范围确认及文档查询咨询

Great question! Your assumption is mostly correct, but there's a small but important detail to add. Let's break this down clearly:

When you compile a C++ program with g++, it automatically links against two key standard libraries by default:

• The GNU C++ Standard Library (libstdc++): This is exactly what you're thinking—all the standard C++ features (STL containers, algorithms, iostream, exception handling, etc.) are part of this library. It's g++'s implementation of the C++ standard, included without needing any extra flags.
• The GNU C Standard Library (libc): Since C++ maintains core compatibility with C, g++ links against the C standard library by default too. This covers core C functions like malloc, printf, and string manipulation routines that the C++ runtime relies on (even if you don't explicitly call them in your code).

Additionally, g++ includes a minimal runtime support layer (part of libstdc++) that handles things like initializing global objects, setting up exception handling, and cleaning up resources when your program exits—this is all part of the default setup.

Any non-standard or third-party libraries (like Boost, Qt, SDL, or custom libraries you've built) are not linked automatically. You have to tell g++ to include them explicitly using flags:

• Use -l<library-name> to link against a system library (e.g., -lboost_system for Boost's system module, -lsdl2 for SDL2).
• For some optional standard components (like the C++ Thread Library on older systems), you might need to add -pthread to enable full threading support.

To get authoritative details on g++'s default behavior and the libstdc++ library:

• Local Man Pages: Run man g++ in your terminal to see command-line options and default linking behavior. For libstdc++, check man libstdc++ (if available on your system) or look for the libstdc++ documentation in the GCC info pages (run info libstdc++).
• GCC Official Docs: The GNU Compiler Collection's official documentation includes comprehensive guides for g++ and libstdc++. These cover everything from default libraries to advanced linking options—they're often included with your GCC installation or accessible through system documentation tools.

内容的提问来源于stack exchange，提问作者AmphotericLewisAcid