ld -lc a.o There are several things wrong with this command line: In general, user-level code should never use ld directly, and always use appropriate compiler front end (gcc here) to perform the link. As you have discovered, the link command line that gcc constructs is quite complicated, and the command line that you’ve accepted … Read more
-Wl,–no-undefined linker option can be used when building shared library, undefined symbols will be shown as linker errors. g++ -shared -Wl,-soname,libmylib.so.5 -Wl,–no-undefined \ -o libmylib.so.1.1 mylib.o -lthirdpartylib
There are several ways to solve this: Pass -Bsymbolic or -Bsymbolic-functions to the linker. This has a global effect: every reference to a global symbol (of function type for -Bsymbolic-functions) that can be resolved to a symbol in the library is resolved to that symbol. With this you lose the ability to interpose internal library … Read more
As you’ve noted, DYLD_LIBRARY_PATH behaves like LD_LIBRARY_PATH on other *nix. However, there is another environment variable you should look at called DYLD_FALLBACK_LIBRARY_PATH. In general, these are (both on osx and linux) suggested only for development use as they can cause symbol lookup errors when you override with a library that does not have the same … Read more
To understand linkers, it helps to first understand what happens “under the hood” when you convert a source file (such as a C or C++ file) into an executable file (an executable file is a file that can be executed on your machine or someone else’s machine running the same machine architecture). Under the hood, … Read more
Static libraries increase the size of the code in your binary. They’re always loaded and whatever version of the code you compiled with is the version of the code that will run. Dynamic libraries are stored and versioned separately. It’s possible for a version of the dynamic library to be loaded that wasn’t the original … Read more
Dynamic linking can reduce total resource consumption (if more than one process shares the same library (including the version in “the same”, of course)). I believe this is the argument that drives its presence in most environments. Here “resources” include disk space, RAM, and cache space. Of course, if your dynamic linker is insufficiently flexible … Read more