为 gcc 链接器指定可选库

Question

gcc (g++) 链接器是否支持一个选项，允许它在无法找到提供给它的某些库时不会失败？ 谢谢， 拉菲

Answer 1

听起来你想要的是来自 ld 手册页的内容：

--allow-shlib-undefined
--no-allow-shlib-undefined
Allows or disallows undefined symbols in shared libraries. This switch is similar to --no-undefined except that it determines the behaviour when the undefined symbols are in a shared library rather than a regular object file. It does not affect how undefined symbols in regular object files are handled.

The default behaviour is to report errors for any undefined symbols referenced in shared libraries if the linker is being used to create an executable, but to allow them if the linker is being used to create a shared library.

The reasons for allowing undefined symbol references in shared libraries specified at link time are that: 
• A shared library specified at link time may not be the same as the one that is available at load time, so the symbol might actually be resolvable at load time.

• There are some operating systems, eg BeOS and HPPA , where undefined symbols in shared libraries are normal. 
The BeOS kernel for example patches shared libraries at load time to select whichever function is most appropriate for the current architecture. This is used, for example, to dynamically select an appropriate memset function.