[Buildroot] host-python link fails due to missing readline

[Buildroot] host-python link fails due to missing readline

[Jeff Gray]

Host machine : Ubuntu 12.04.2 x86_64
Buildroot : 2015.11.1
Target : arm920t
Build fail : host-python-2.7.10

Build stopped with an error during host-python:
Failed to build these modules:
readline

I can see that readline-6.3 has been built for target, but not host. In the
log file, I see these references to not finding readline as expected in the
host-python configuration stage:
checking how to link readline libs... none
checking for rl_callback_handler_install in -lreadline... no
checking for rl_pre_input_hook in -lreadline... no
checking for rl_completion_display_matches_hook in -lreadline... no
checking for rl_completion_matches in -lreadline... no

And then later in the build process, because readline is not there:
running build_ext
/usr/lib/libreadline.so: not an ELF file.

Then when trying to build the readline Python extension (shortened for
readability):
building 'readline' extension
/usr/bin/gcc ... -c /output/build/host-python-2.7.10/Modules/readline.c ...
(some warnings but nothing serious)
/usr/bin/gcc -pthread -shared readline.o ... -lreadline -lncurses
-lpython2.7 -o readline.so
/usr/bin/ld: skipping incompatible
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libreadline.so when
searching for -lreadline
/usr/bin/ld: skipping incompatible /usr/lib/../lib/libreadline.so when
searching for -lreadline
/usr/bin/ld: skipping incompatible
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../libreadline.so when searching
for -lreadline
/usr/bin/ld: skipping incompatible /usr/lib/libreadline.so when searching
for -lreadline
/usr/bin/ld: cannot find -lreadline
collect2: ld returned 1 exit status

There is no /output/host/usr/lib/gcc/x86_64/ directory. Should there be one?

I'm experienced with embedded development, but new to buildroot, so forgive
me an obvious error. I have searched through the list archives for similar
issues, but can't find anything since a similar problem that was reported
fixed by a Python update (the patch which is no longer part of buildroot).
http://lists.busybox.net/pipermail/buildroot/2014-April/094460.html

I'm not sure what area to look at for this issue. Should readline be built
for host before the host-python build? Or is it a config error in
host-python looking for something that isn't there?

My .config file is on Google Drive here: https://goo.gl/gLj4rM
My full build log file (16MB) is here: https://goo.gl/NLDCOj
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[Buildroot] host-python link fails due to missing readline

[Arnout Vandecappelle]

On 29-01-16 01:08, Jeff Gray wrote:
> Host machine : Ubuntu 12.04.2 x86_64
> Buildroot : 2015.11.1
> Target : arm920t
> Build fail : host-python-2.7.10
> 
> Build stopped with an error during host-python:
> Failed to build these modules:
> readline
> 
> I can see that readline-6.3 has been built for target, but not host. In the log
> file, I see these references to not finding readline as expected in the
> host-python configuration stage:
> checking how to link readline libs... none
> checking for rl_callback_handler_install in -lreadline... no
> checking for rl_pre_input_hook in -lreadline... no
> checking for rl_completion_display_matches_hook in -lreadline... no
> checking for rl_completion_matches in -lreadline... no 
> 
> And then later in the build process, because readline is not there:
> running build_ext
> /usr/lib/libreadline.so: not an ELF file.

 That is just weird... For two reasons:
- it shouldn't try to link with readline to begin with;
- since this is host compilation, /usr/lib/readline.so should be OK.

 What is also weird is that configure can't find readline, but the compilation
doesn't complain about missing header files.

 Can you check from which package /usr/lib/readline.so is coming?
dpkg -S /usr/lib/readline.so

 Does your gcc somehow generate 32bit code? Are you running inside some kind of
container that could affect things?

 It may also be useful to look at the config.log of python.


> 
> Then when trying to build the readline Python extension (shortened for readability):
> building 'readline' extension
> /usr/bin/gcc ... -c /output/build/host-python-2.7.10/Modules/readline.c ...
> (some warnings but nothing serious)
> /usr/bin/gcc -pthread -shared readline.o ... -lreadline -lncurses -lpython2.7 -o
> readline.so
> /usr/bin/ld: skipping incompatible
> /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libreadline.so when searching
> for -lreadline
> /usr/bin/ld: skipping incompatible /usr/lib/../lib/libreadline.so when searching
> for -lreadline
> /usr/bin/ld: skipping incompatible
> /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../libreadline.so when searching for
> -lreadline
> /usr/bin/ld: skipping incompatible /usr/lib/libreadline.so when searching for
> -lreadline
> /usr/bin/ld: cannot find -lreadline
> collect2: ld returned 1 exit status 
> 
> There is no /output/host/usr/lib/gcc/x86_64/ directory. Should there be one?

 Why do you mention this directory?


 Regards,
 Arnout


> 
> I'm experienced with embedded development, but new to buildroot, so forgive me
> an obvious error. I have searched through the list archives for similar issues,
> but can't find anything since a similar problem that was reported fixed by a
> Python update (the patch which is no longer part of buildroot).
> http://lists.busybox.net/pipermail/buildroot/2014-April/094460.html
> 
> I'm not sure what area to look at for this issue. Should readline be built for
> host before the host-python build? Or is it a config error in host-python
> looking for something that isn't there?
> 
> My .config file is on Google Drive here: https://goo.gl/gLj4rM
> My full build log file (16MB) is here: https://goo.gl/NLDCOj
> 
> 
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot
> 


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] host-python link fails due to missing readline

[Jeff Gray]

Thanks for your reply - that helped push me in the right direction. I
wasn't sure that buildroot used my local system libraries - I thought maybe
it just used the files built in output/host/. But it does make sense that
it does.

I found that the local /usr/lib/libreadline.so was an ARM executable (the
only one in any system directory)... This is obviously not a good thing,
which is why it was telling me incompatible file.

I don't know for sure how this happened, but I suspect one of the previous
developers who used this system accidentally copied an ARM file to the
system lib and not his cross development lib & didn't realise it. So this
file has been sitting there for 2.5 years waiting to go off.

Sorry to waste your time - thanks for the help in finding it. I will now do
a clean make and see how it goes.
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