Re: Why does libca.so depend on libreadline.so?

["Dmitry Yu. Bolkhovityanov via Tech-talk" <tech-talk at aps.anl.gov>]

Hi Simon,

On Fri, 12 May 2023, Simon Rose wrote:

> Hi Dmitry -
>
> I do not get the same results as you. When I build various version of EPICS base (e.g. 7.0.4, 7.0.5) for linux-x86_64, libCom also depends on readline at that point. I don't think the change that Michael linked is the source of this dependency.
The key is 7.0.7: even 7.0.6.1's libCom.so does have a dependency on 
libreadline.so, while 7.0.7 do not.
How Michael's patch achieves such an effect -- that's another question.  I 
still don't understand the mechanism; I even did a "diff -Naurb 
base-7.0.6.1 base-7.0.7" (just sources, of course) and there's nothing 
regarding "readline" besides what patch does.
In short -- as I understood it -- the patch just moves the "readline 
detection" from makefiles (which checked for 
.../include/readline/readline.h presence) into .c-files (via 
__has_include() builtin).
But how the detection method (which is orthogonal to dependence) manages 
to relieve libCom.so from libreadline.so dependency -- I yet have to 
fugure out.
With best regards,
Dmitry