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

[Mark Rivers via Tech-talk <tech-talk at aps.anl.gov>]

• 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.

I now recall that when I built my IOCs with base 7.0.7 command line recall did not work on Centos 7.  The automatic detection of the readline support does not work with older versions of gcc.

I posted the issue to core-talk:

https://epics.anl.gov/core-talk/2022/msg00381.php

Thus, on the advice of Michael Davidsaver I made this edit:

diff --git a/configure/toolchain.c b/configure/toolchain.c

index 2f76b475b..da4e8bb2c 100644

--- a/configure/toolchain.c

+++ b/configure/toolchain.c

@@ -45,5 +45,5 @@ COMMANDLINE_LIBRARY ?= READLINE

 COMMANDLINE_LIBRARY ?= EPICS

 #  endif

 #else

-COMMANDLINE_LIBRARY ?= EPICS

+COMMANDLINE_LIBRARY ?= $(strip $(if $(wildcard $(if $(GNU_DIR),$(GNU_DIR)/include/readline/readline.h)), READLINE, EPICS))

 #endif

With that edit command line recall does work, and base 7.0.7 libCom.so does depend on libreadline.

This is base 7.0.7 on Centos 7.  It depends on libreadline.so.6.

corvette:local/epics-devel/base-7.0.7>ldd lib/linux-x86_64/libCom.so

        linux-vdso.so.1 =>  (0x00007ffe673d6000)

        libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f171eec5000)

        libreadline.so.6 => /lib64/libreadline.so.6 (0x00007f171ec7f000)

        librt.so.1 => /lib64/librt.so.1 (0x00007f171ea77000)

        libdl.so.2 => /lib64/libdl.so.2 (0x00007f171e873000)

        libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f171e56b000)

        libm.so.6 => /lib64/libm.so.6 (0x00007f171e269000)

        libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f171e053000)

        libc.so.6 => /lib64/libc.so.6 (0x00007f171dc85000)

        /lib64/ld-linux-x86-64.so.2 (0x00007f171f355000)

        libtinfo.so.5 => /lib64/libtinfo.so.5 (0x00007f171da5b000)

This is base 7.0.7 on Centos 8.  It depends on libreadline.so.7.

Last login: Sun Apr 30 16:49:17 2023 from 164.54.160.82

[epics@viper ~]$ cd /corvette/usr/local/epics-devel/base-7.0.7

[epics@viper base-7.0.7]$ ldd lib/linux-x86_64-centos8/libCom.so

        linux-vdso.so.1 (0x00007ffc88315000)

        libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fa3a7c94000)

        libreadline.so.7 => /lib64/libreadline.so.7 (0x00007fa3a7a45000)

        librt.so.1 => /lib64/librt.so.1 (0x00007fa3a783d000)

        libdl.so.2 => /lib64/libdl.so.2 (0x00007fa3a7639000)

        libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007fa3a72a4000)

        libm.so.6 => /lib64/libm.so.6 (0x00007fa3a6f22000)

        libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007fa3a6d0a000)

        libc.so.6 => /lib64/libc.so.6 (0x00007fa3a6945000)

        /lib64/ld-linux-x86-64.so.2 (0x00007fa3a812a000)

        libtinfo.so.6 => /lib64/libtinfo.so.6 (0x00007fa3a6718000)

This is Ubuntu 22.  It depends on libreadline.so.8.

TahoeU18:/corvette/usr/local/epics-devel/base-7.0.7> ldd lib/linux-x86_64-ub18/libCom.so

        linux-vdso.so.1 (0x00007ffc6bbf9000)

        libreadline.so.8 => /lib/x86_64-linux-gnu/libreadline.so.8 (0x00007f2b0101d000)

        libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f2b00df3000)

        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f2b00d0c000)

        libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f2b00cec000)

        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f2b00ac2000)

        libtinfo.so.6 => /lib/x86_64-linux-gnu/libtinfo.so.6 (0x00007f2b00a90000)

        /lib64/ld-linux-x86-64.so.2 (0x00007f2b0110a000)

---

From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Dmitry Yu. Bolkhovityanov via Tech-talk <tech-talk at aps.anl.gov>
Sent: Friday, May 12, 2023 9:29 AM
To: Simon Rose <Simon.Rose at ess.eu>
Cc: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Re: Why does libca.so depend on libreadline.so?

 

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