CODEWITHSUNDEEP
cross-compilinggnugnu-makeautomake
zmb
zmb

Reputation: 7867

Cross compiling with automake

I'm trying to cross compile a project and a library it depends on for use on an embedded system. Both the application and the dependency use automake. I was able to compile the library without much issue.

./configure --host=powerpc-none-linux-gnuspe --prefix=/home/me/build_dir
make
make install

I used --prefix so that make install didn't put the outputs in my filesystem with all of the x86 libs. I have also tried running configure without --prefix and instead setting the DESTDIR environment variable before running make install. They appear to do the same thing. I want to be able to tar up /home/me/build_dir and drop it on the root of the embedded target's file system. I'm hoping that --prefix didn't hard code an absolute path on my host machine somewhere.

Then I tried to cross compile the application that uses this library:

./configure --host=powerpc-none-linux-gnuspe --with-sysroot=/home/me/build_dir

I ran into 2 things. The configure script completed successfully but the first make failed because it couldn't find one of the headers. It is looking under /usr/include instead of /home/be/build_dir/usr/include. Shouldn't the --with-sysroot option also modify the include directories or am I missing something?

Also, I'm getting a warning 

libtool: link: warning: library libstdc++.la was moved

I get the feeling that I've missed something. Is this warning something I can safely ignore or did I mess up somewhere?

To summarize my questions: 1) Is there a difference between ./configure --prefix=x and make DESTDIR=x install? 2) What's the right way to update the search path for the library headers? 3) Why am I getting the warning about libstdc++ and is it something I should worry about?

Upvotes: 4

Views: 8388

Answers (1)

MadScientist
MadScientist

Reputation: 100781

For your situation you should use DESTDIR. Setting --prefix will mean the resulting program will expect to be installed at the location in --prefix. DESTDIR on the other hand is a purely make install artifact, it just prefixes that to the beginning of every path when it installs. The resulting product still expects to be installed at the --prefix location. If you want to install the results on the target host, set --prefix to the place it will go and use DESTDIR to stage it somewhere else.

I believe that just setting --sysroot in the configure script is not sufficient, but I'm not sure. I think that sets the sysroot while configure runs but it doesn't set the makefile.

What I usually do is create a shell script wrapper for the compiler which invokes the real compiler with the proper --sysroot=dir option, then use that wrapper as the compiler name to configure. It's simpler to do it that way, than to try to get all invocations of the compiler to add the --sysroot flag externally.

I'm not sure about the libstdc++ warning. libstdc++ is a part of the compiler, not part of the sysroot...?

ETA:

By script wrapper I mean create a script named something like sysroot-gcc:

#!/bin/sh
exec real-gcc --sysroot=/some/sysroot "$@"

then you can run configure CC=sysroot-gcc. You can make this as fancy as you want to; I have a generic script that parses the name ($0) and obtains the sysroot name and the tool name (gcc, g++, etc.) from it so I can reuse that one script for all tools.

Upvotes: 4

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