I have a set of more or less portable C/C++ sources sitting on a Linux development host that I would like to be able to:
compile for 32- and 64-bit Linux targets
cross-compile for 32- and 64-bit Windows targets
cross-compile for 32- and 64-bit Mac targets
and, ideally, without any runtime dependencies on other emulation DLL's like cygwin1.dll, MinGW, etc though I could use them if there's no other choice. If I have to use them, I'd prefer statically linking their functionality to my code.
The target binary that is desired is:
a shared library (.so) for Linux and Mac targets, and
a DLL for Windows.
I have no idea how to build a cross-compiler (and the associated toolchain) from scratch. I'm hearing that pre-built cross-compiler toolchains are available for various host-and-target combinations, but I don't know where to find them, or even how to use them without running into runtime crashes/coredumps later due to pointer model subtleties (LP64, LLP64, etc), specifying wrong or inadequate compiler switches, other misconfiguration, etc.
I've so far been unable to find the relevant and complete information on the above, and whatever little I've managed to find is scattered all over the place in so many bits and pieces that I'm not even sure if all that I've read is complete or even correct (applies fully, no more no less to my case).
I'm not a compilers expert, just their regular user. Would appreciate information achieving the above compilation goals.
I would like to cross compile a library for Mac OsX on Linux and I am considering imcross. The instructions in the site are simple, but everytime you setup a crosscompiling environment you have to fix a lot of things, so I won't expect that it will be straightforward. You can check in the website that there are some limitations to this project but it is the best I came across.
Not being a priority for me now (I have other stuff to do before performing this task) I didn't setup the crossenvironment yet. I am going to do that in few days time.
Related
I've done all my development work for an embedded linux device (gumstix) in a linux VM and I would like to move the code base to my host Linux computer. The cross-compiler was setup prior to me inheriting the codebase, so I'm not sure how the compiler was set up. I have some questions concerning how to set up the cross-compiler.
The compiler on the VM is a arm-linux-gnueabihf-gcc.
Is the cross-compiler kernel specific? (Using linux kernel 3.17)
Is the cross-compiler target device specific; i.e. do I need to use a gumstix compiler or is the arm-linux-gnueabihf-gcc satisfactory. Does this compiler need to be configured manually.
Is there a way to see/import the configuration setting of the working VM compiler?
Does the arm-linux-gnueabihf-gcc use the same standard library source code as the gcc compiler?
I've seen varying approaches to setting up cross-compilers on web. Where can I find comprehensive information for setting up a cross-compiler (More than a how-to, but also explains why).
Thank you
The cross compiler is not kernel specific nor target device specific. It is specific to the architecture of the SoC or processor you are targeting. So if your current compiler is arm-linux-gnueabihf-gcc it implies it can compile code for ARM32 processors which have floating point support in hardware. Depending on your host Linux system, you can install a similar compiler using the package manager or you may also download it from here.
Different people probably will recommend different approaches and also on whether a particular approach is easy or difficult. Regardless I tend to recommend building the complete target image and generating an SDK for doing development using something like Yocto/Openembedded or Buildroot.
Not sure exactly what you mean by Q4.
I want to install a driver for Ros (robot operating system), and I have two options the binary install and the compile and install from source. I would like to know which installation is better, and what are the advantages and disadvantages of each one.
Source: AKA sourcecode, usually in some sort of tarball or zip file. This is RAW programming language code. You need some sort of compiler (javac for java, gcc for c++, etc.) to create the executable that your computer then runs.
Advantages:
You can see what the source code is which means....
You can edit the end result program to behave differently
Depending on what you're doing, when you compile, you could enable certain optimizations that will work on your machine and ONLY your machine (or one EXACTLY like it). For instance, for some sort of gfx rendering software, you could compile it to enable GPU support, which would increase the rendering speed.
You can create a version of an application for a different OS/Chipset (see Binary below)
Disadvantages:
You have to have your compiler installed
You need to manually install all required libraries, which frequently also need to be compiled (and THEIR libraries need to be installed, etc.) This can easily turn a quick 30-second command into a multi-hour project.
There are any number of things that could go wrong, and if you're not familiar with what the various errors mean, finding support online could be quite difficult.
Binary: This is the actual program that runs. This is the executable that gets created when you compile from source. They typically have all necessary libraries built into them, or install/deploy them as necessary (depending on how the application was written).
Advantages:
It's ready-to-run. If you have a binary designed for your processor and operating system, then chances are you can run the program and everything will work the first time.
Less configuration. You don't have to set up a whole bunch of configuration options to use the program; it just uses a generic default configuration.
If something goes wrong, it should be a little easier to find help online, since the binary is pre-compiled....other people may be using it, which means you are using the EXACT same program as them, not one optimized for your system.
Disadvantages:
You can't see/edit the source code, so you can't get optimizations, or tweak it for your specific application. Additionally, you don't really know what the program is going to do, so there could be nasty surprises waiting for you (this is why Antivirus is useful....although LESS necessary on a linux system).
Your system must be compatible with the Binary. For instance, you can't run a 64-bit application on a 32-bit operating system. You can't run an Intel binary for OS X on an older PowerPC-based G5 Mac.
In summary, which one is "better" is up to you. Only you can decide which one will be necessary for whatever it is you're trying to do. In most cases, using the binary is going to be just fine, and give you the least trouble. Sometimes, though, it is nice to have the source available, if only as documentation.
I intend to cross compile for Raspberry Pi, basically a small ARM computer. The host will be an i686 box running Arch Linux.
My first instinct is to use cross compiler provided by Arch Linux, arm-elf-gcc-base and arm-elf-binutils. However, every wiki and post I read seems to use some version of custom gcc build. They seem to spend significant time on cooking their own gcc. Problem is that they never say WHY it is important to use their gcc over another.
Can stock distro provided cross compilers be used for building Raspberry Pi or ARM in general kernels and apps?
Is it necessary to have multiple compilers for ARM architecture? If so, why, since single gcc can support all x86 variants?
If 2), then how can I deduce what target subset is supported by a particular version of gcc?
More general question, what general use cases call for custom gcc build?
Please be as technical as you can, I'd like to know WHY as well as how.
When developers talk about building software (cross compiling) for a different machine (target) compared to their own (host) they use the term toolchain to describe the set of tools necessary to build binary files. That's because when you need to build an executable binary, you need more than a compiler.
You need routines (crt0.o) to initialize runtime according to requirements of operating system and standard libraries. You need standard set of libraries and those libraries need to be aware of the kernel on target because of the system calls API and several os level configurations (f.e. page size) and data structures (f.e. time structures).
On the hardware side, there are different set of ARM architectures. Architectures can be backward compatible but a toolchain by nature is binary and targeted for a specific architecture. You can have the most widespread architecture by default but then that won't be too fruitful for an already constraint environment (embedded device). If you have the latest architecture, then it won't be useful for older architecture based targets.
When you build a binary on your host for your host, compiler can look up all the necessary bits from its own environment or use what's on the host - so most of the above details are invisible to developer. However when you build for a different target than your host type, toolchain must know about hardware, os and standard library details. The way you tell these to toolchain is... by building it according to those details which might require some level of bootstrapping. (or you can do this via extensive set of parameters if toolchain supports / built for it.)
So when there is a generic (stock) cross compile toolchain, it has already some target specifics set and that might not meet your requirements. Please see this recent question about the situation on Ubuntu for an example.
For a university course I have to write a http server which is supposed to run on both Linux and Windows.
I have got a humble Linux machine which I don't think can handle any kind of heavy virtual environment, neither I'm willing to go through the hassle of installing it.
This is the first project of mine complex enough (I estimate ~1.5 months to develop) to require an environment sufficiently comfortable to alternate rapidly between short coding and testing sessions (the latter on both platforms, of course).
So, I was wondering what could be the best set up for this situation. I think testing it on Wine would be ok (it is not a real-world thing, after all), and I installed MinGW for the Windows-targeting part.
Basically, a simple well-written makefile could solve my problem... It should build both the Linux and Windows binaries and place them in the respective folders (the Windows one in the Wine sub-tree) and I'm all done! But I feel very inexperienced in this thing and I really don't know where to start. Maybe the make manual, ahah!:)
Thoughts, suggestions, anything I didn't think/know!
Thank you!
(PS. I'm planning to use emacs as editor, or maybe learn vim. Unless eclipse provide some kind of skynet-like plugin that entirely solve this problem...:)
You're on the right track. It's not that complicated, really, thanks to MinGW. You basically need two things:
The code has to be portable across the OSes. MinGW has some POSIX support, but you'll probably need to either use Cygwin in order to be able to use the POSIX interface or have your own compatibility layer for interfacing with the OS. I'd probably go for Cygwin as then you can code only against POSIX and won't have to test and debug your compatibility layer. Also, make sure you won't use any external libraries that are OS specific. Non-portable code often results in a compile error, but make sure you test the application thoroughly anyway.
The toolchains for targeting Linux and Windows. You already have them, you just need to use them correctly. Normally you'd use a variable like $(CROSS_COMPILE) as a prefix when calling the toolchain during cross compilation. So when compiling for Linux, you call gcc, ld, etc. (having the CROSS_COMPILE variable empty), and when compiling for Windows you call e.g. i486-mingw32-gcc, i486-mingw32-ld etc., i.e. CROSS_COMPILE=i486-mingw32-. Or just just define CC, LD etc. depending on the target.
I wrote a small game on Linux and made it run on Windows as well. If you browse the code, you can see the code has next to no #ifdef jungle (basically just some extra debugging features enabled for Linux), and the Makefile is simple as well, with no complicated handling for cross-compilation, just the possibility to override CC etc. like it should be. As lots of important open source software is written this way (especially software that's used by the desktop and embedded devices), you should also be able to find lots of other examples on how to set up the build environment correctly.
As for testing the application on Windows, I think the best option is if you can find a real Windows machine somehow. If you do everything correctly, it should run the same as on Linux and you won't need to continuously test your application on both OSes. If testing on a Windows machine is not possible, a VM would be the next best choice, though it would probably be more difficult to set it up. Wine is a good backup plan, but I don't think you can be sure your application works well on Windows if you only tested it on Wine.
Reference this question about compiling. I don't understand how my program for Mac can use the right -arch, compile with those -arch flags, the -arch flags be for the system I am on (a ppc64 g5), and still produce the wrong object code.
Also, if I used a cross compiler and was on Linux, produced 10.5 code for mac, how would this be any different than what I described above?
Background is that I have tried to compile various apache modules. They compile with the -arch ppc, ppc64, etc. I get no errors and I get my mod_whatever.so. But, apache will always complain that some symbol isn't found. Apparently, it has to do with what the compiler produces, even though the file type says it is for ppc, ppc64, i386, x_64 (universal binary) and seems to match all the other .so mods I have.
I guess I don't understand how it could compile for my system with no problem and then say my system can't use it. Maybe I do not understand what a compiler is actually giving me.
EDIT: All error messages and the complete process can be seen here.
Thank you.
Looking at the other thread and elsewhere and without a G5 or OSX Server installation, I can only make a few comments and suggestions but perhaps they will help.
It's generally not a good idea to be modifying the o/s vendor's installed software. Installing a new Apache module is less problematic than, say, overwriting an existing library but you're still at the mercy of the vendor in that a Software Update could delete your modifications and, beyond that you have to figure out how the vendor's version was built in the first place. A common practice in the OS X world is to avoid this by making a completely separate installation of an open source product, like Apache, using, for instance, MacPorts. That has its cons, too: to achieve a high-level of independence, MacPorts will often download and build a lot of dependent packages for things which are already in OS X but there's no harm in that other than some extra build cycles and disk space.
That said, it should be possible to build and install apache modules to supplement those supplied by Apple. Apple does publish the changes it makes to open source products here; you can drill down in the various versions there to find the apache directory which contains the source, Makefile and applied patches. That might be of help.
Make sure that the mod_*.so you build are truly 64-bit and don't depend on any non-64 bit libraries. Use otool -L mod_*.so to see the dynamic libraries that each references and then use file on those libraries to ensure they all have ppc64 variants.
Make sure you are using up-to-date developer tools (Xcode 3.1.3 is current).
While the developer tool chain uses many open source components, Apple has enhanced many of them and there are big differences in OS X's ABIs, universal binary support, dynamic libraries, etc. The bottom line is that cross-compilation of OS X-targeted object code on Linux (or any other non-OS X platform) is neither supported nor practical.