[CMake] cross-compile and find_library

[Davis Ford]

Let me take another shot at this -- I created a gist that highlights the
problem: https://gist.github.com/3789287

I am supporting cross-compile for the Raspberry Pi Arm target in my
project, but I also build regularly on plain 'ol x86 linux so I can test
w/o having to go to the target.  The Pi is awful slow at compilation, so I
want to do cross-compile also on Linux x86.

I am using 3rd party libraries from http://zeromq.org -- I have already
compiled them on the target hardware and checked them in to my project repo
directory structure:

Same libraries, compiled for different targets, stored in different paths
in my project directory structure.

I created a Toolchain file to cross-compile.  So far that works fine, until
I want to go linking against the zeromq libraries.

Compiling for Linux/x86 works fine, and even compiling for Mac OS X but
when I run my Toolchain to cross-compile, it complains that it cannot find
the libraries for the target.  I run the toolchain like this:

$ cmake -DCMAKE_TOOLCHAIN_FILE=../Toolchain-raspberrypi-arm.cmake ..
Using Raspberry Pi Tools found in
/home/davis/git/raspberrypi/toolsCMAKE_CROSSCOMPILING =>
TRUECMAKE_SYSTEM_NAME => Linux, PROJECT_SOURCE_DIR =>
/home/davis/git/ebike-firmware
CMAKE_CROSSCOMPILING is true...doing find_library for ZeroMQ...
CMake Error: The following variables are used in this project, but
they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the
CMake files:
CZMQ_LIB
    linked by target "Runtime" in directory /home/davis/git/ebike-firmware/src
ZEROMQ_LIB
    linked by target "Runtime" in directory /home/davis/git/ebike-firmware/src

-- Configuring incomplete, errors occurred!

The libraries, are indeed there.  I thought using the
CMAKE_FIND_ROOT_PATH_MODE_LIBRARY
and the CMAKE_FIND_ROOT_PATH would force CMake to use an explicit path to
try to resolve libraries when you execute find_library, but even though the
files are there, it fails with NOTFOUND.  Does it somehow inspect the
binary and consider its current architecture -- if it isn't a match, it
reports fail / NOTFOUND -- if so, how can I work around this?

Is there a better way to do what I'm trying to do??


On Mon, Sep 24, 2012 at 5:38 PM, Davis Ford <davisford at gmail.com> wrote:

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