When i should use ld instead of gcc?

问题:

I want to know when i should use ld linker instead off gcc. I just wrote a simply hello world in c++, of course i include iostream library. If i want make a binary file with gcc i just use:

g++ hello hello.cpp and i've got my binary file.

Later i try to use ld linker. To get object file i use: g++ -c hello.cpp. Ok that was easy, but the link command was horrible long:

ld -o hello.out  hello.o \
   -L /usr/lib/gcc/x86_64-linux-gnu/4.8.4/ \
   /usr/lib/gcc/x86_64-linux-gnu/4.8.4/crtbegin.o \
   /usr/lib/gcc/x86_64-linux-gnu/4.8.4/crtend.o \
   /usr/lib/x86_64-linux-gnu/crti.o \
   /usr/lib/x86_64-linux-gnu/crtn.o \
   /usr/lib/x86_64-linux-gnu/crt1.o \
   -dynamic-linker /lib64/ld-linux-x86-64.so.2 -lstdc++ -lc 

I know fact that gcc uses the ld. Using gcc is better in all cases or just in most cases? Please, tell me somethink about cases where ld linker has advantage.

回答1:

As you mentioned, gcc merely acts as a front-end to ld at link time; it passes all the linker directives (options, default/system libraries, etc..), and makes sure everything fits together nicely by taking care of all these toolchain-specific details for you.

I believe it's best to consider the GNU toolchain as a whole, tightly integrated environment (as anyone with an experience of building toolchains for some exotic embedded platforms with, say, dietlibc integration will probably agree).

Unless you have some very specific platform integration requirements, or have reasons not to use gcc, I can hardly think of any advantage of invoking ld directly for linking. Any extra linker-specific option you may require could easily be specified with the -Wl, prefix on the gcc command line (if not already available as a plain gcc option).

回答2:

It is mostly a matter of taste: you would use ld directly when the command-lines are simpler than using gcc. That would be when you are just using the linker to manipulate a small number of shared objects, e.g., to create a shared library with few dependencies.

Because you can pass options to ld via the -Wl option, often people will recommend just using gcc to manage the command-line.