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Re: [paho-dev] not a shared executable
On 08/23/2013 06:18 AM, Ian Craggs wrote:
How would using automake/autoconf help with cross-compiling?  I've never used them, so I don't know.  I was under the impression that they helped if you had a lot of dependencies, which these libraries don't - only gcc.

The "--build" and "--host" options to the configure script allow you to set things up each time you compile. You set the build to your PC and the host to the target platform/compiler, like:
./configure --build=i686-pc-linux-gnu --host=arm-eabi
By making them different, it knows that you're cross-compiling and will use the compiler "arm-eabi-gcc", and so on.

You can also use the "--prefix" option to set the install directory, so that you can have a bunch of different versions on your computer (one for Raspberry Pi, one for Beaglebone, etc).
./configure --build=i686-pc-linux-gnu --host=arm-linux --prefix=/opt/xlibs/arm-linux
If you compile natively on any platform, you don't worry about the settings. Just:
./configure
After you configure, you run "make" and "make install", and the libraries are where you requested.


I think the problem is that are so many combinations of processors, EABIs, Linux or other Unix kernel levels, C libraries and versions (uclibc as well as glibc for example), that deciding on the targets we wanted to build for would be impossible. 

That's the beauty of this... You don't have to worry about the different targets, assuming that they are Linux/gcc.

And it is very consistent across libraries. A very large percentage of Linux libraries can be cross-compiled in this manner, whether or not that was the author's intent. It just works.


If you are running an OS in the configuration you want, and you have gcc, it is easy to build - at least for Linux/Unix.  If I want to compile for Pi or whatever, I clone the source with git and make - job done.

With just a makefile, someone new would have to start searching through the file to find out how to cross-compile. With a configure script, it's consistent with much of the rest of the Linux world.



For Windows I prefer the Microsoft compilers, as in my experience they produce better code.  And most developers will also be using Visual Studio.  A Visual Studio project is the obvious solution, no?

Recently I've been setting up Eclipse Hudson system to build and test the C clients, for Linux 64-bit (see https://hudson.eclipse.org/hudson/job/paho-c-dev-nightly/ - the test failures are because we're still setting up the SSL test environment).  I've used Ant, as that seemed to coexist with Hudson nicely.  Proliferating build methods, however, doesn't seem desirable.

Agreed, this is only for Linux, mainly for gcc. Some other system, such as Ant my encompass both. But most Linux C developers are probably not familiar with using Ant.

Frank

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