Re: [PATCH] Makefile: Compute libraries for libqemuutil.a and libvhost-user.a

[Michael Tokarev]

01.07.2020 12:12, Christophe de Dinechin wrote:
..
>>>  # Build libraries
>>>
>>> +libqemuutil.a-libs += $(call extract-libs, $(util-obj-y) $(trace-obj-y) 
>>> $(stub-obj-y))
>>> +libvhost-user.a-libs += $(call extract-libs, $(libvhost-user-obj-y) 
>>> $(util-obj-y) $(stub-obj-y))
..
>> Another thing I wonder about: the purpose of the .a files is to compile
>> all object files and only link those .o files needed by the program
>> (i.e. a subset of the .a file).
> 
> I believe that what you are saying is that by passing the required libraries
> automatically, the binaries that use libqemuutil.a will inherit undesired
> ldd dependencies. Indeed, a quick experiment shows that if you pass a -l
> option, the library dependency is recorded even if no symbol in that library
> is used. I saw no obvious linker option to address that.

There's --as-needed and --no-as-needed ld flag (used with cc as 
-Wl,--as-needed),
which is designed for this very case.

JFYI.

/mjt