I have a library compiled into a .a file, linked against my application. (iphone, developing with Xcode)
Everything seems to be fine, linking seems to succeed, but when I run the program it crashes. The point of crash is at a memcmp() call in the statically linked library. The debugger shows all kind of stuff called with "dyld" in their names, so it seems that for whatever reason it can not resolve memcmp, starts looking for dynamic libraries, then fails.
AFAIK memcmp is in libc, so should not be a problem. (tried also passing -lc to the linker, and it did not help, just as I expected)
So how it is supposed to work? Why can't a statically linked library use anything from libc? How should I compile it?
Thank you
libc is apparently dynamically linked on your platform. A matching version cannot be found at runtime to satisfy the dependency generated at link time.
I can't explain how this would happen other than filesystem corruption or calling chroot before the dynamic linking happens (which would seem unlikely).
Perhaps someone will find it useful if I share what the problem was:
The library was not compiled for the same OS version as the main program, so it was expecting a different libc than what it found when running.
Related
I would like to write a program using Scala Native but it has to run on a linux host (centos 6.5) with a very old glibc. So I would like to deploy that program as a statically linked executable, e.g. as golang does.
How do I build a statically linked executable with scala-native? Is it possible? If yes, how do I do it? If no, why not?
The sbt option nativeLinkingOptions takes a Seq[String] of extra arguments which are passed verbatim to clang during linking.
Adding the following to the project build settings works for me in a quick test:
nativeLinkingOptions += "-static"
I'm not an expert on this topic, but from what I understand that's not something that can be done for all kinds of applications, it might be even impossible to do based on what are your dependency libraries;
For example you cannot statically link against glibc (it's not designed to be statically linkable and has dynamic features like nss that prevents it from being linked statically).
You can try another libc implementation like musl which is statically linkable, however you need to compile a lot of things from scratch and in the end, your output binary might have some weird behaviors, for example name resolution might not work and you need to use direct IP addresses, unless you use a resolver library too.
That's a rabbit hole you probably don't want to go to!
But, if you are also an experienced C/C++ developer, you can tweak with linker parameters as mentioned in the other answer; however you might need to link manually, as currently available sbt options does not allow you to change order of existing linking parameters, which is unfortunately important when linking statically!
I'm pretty new to c++ (and programming in general) and I'm currently trying to inlcude the "SDL.h" header into a c++ project in Eclipse (I use minGW btw). I've provided the project with the paths to the the header files and the library of SDL. However, whenver I specifically include "SDL.h" and the build then project I get the following Message:
" 'Launching SDL Basic.exe' has encountered a problem. Program file does not exist. "
I'm pretty sure that this has to do with the fact that no .exe file is generated whenever I build the project with SDL.h included. What I don't get is why this happens. When I include some other SDL header, such as SDL_assert, this is not a problem. Then the .exe file is generated just as usual and the program runs just as it should.[enter image description here][1]
http://i.stack.imgur.com/cdV8U.jpg How it looks when SDL.h is included.
http://i.stack.imgur.com/MW7PX.jpg How it looks when something else from SDL is included.
I seem to have fixed the problem. Whenever I ran the program the console window outout " undefined reference to 'Winmain#16' ". So I googled on it and found out that SDL defines its own main function in SDL_main.h, which in total would give me two main functions. To prevent SDL from defining its own main function I had to define the macro SDL_MAIN_HANDLED before I included SDL.h, and look, it worked:
http://i.stack.imgur.com/mNOOE.jpg
If someone can explain this in more detail I'd really appreciate it.
I did a little research and it looks like the undefined reference to WinMain#16 is because SDL is automatically creating a Windows entry point for your application, but you haven't provided the necessary libraries to link in the SDL implementation of that entry point. However, if you intend to use the SDL functionality, you really do need that entry point, because it performs several important initialization steps necessary to leverage the SDL features that you presumably want to use.
Defining SDL_MAIN_HANDLED is a mechanism that would allow you to provide your own Windows entry point (i.e.: WinMain), but that is a more complicated approach (albeit more flexible). This only solves your problem because it happens to prevent "main" from being redefined to "SDL_main" which in turn means that your .cpp file no longer even requires any of the SDL libraries. So it compiles and links, but you won't have any of the SDL functionality you're looking for.
You need to link in the appropriate libraries. See here - it provides some info that might help.
There is a relatively-new lightweight JVM called Avian that can produce executables for iOS targets.
There isn't too much documentation on the website (and not much can be found searching with Google). I was wondering if anybody was aware of a step-by-step tutorial on how to get a basic Scala program running on iOS, using Avian.
Another alternative JVM to iOS compiler is RoboVM. Although it is at an early stage, it looks quite promising, with examples on how to compile Scala for iOS.
EDIT This was an old answer, valid at that time, but, as #JamesMoore points out, RoboVM is no more. What looks very promising now, and may well be the way to run Scala code in iOS in the near future is Scala Native
Compiled Scala sources are completely standard class files. You should be able to follow the instructions (look for “Embedding”) on the website without large changes, just treat scala-library.jar as a dependency of your code.
I managed to bootstrap the complete compiler and the standard library running on Avian a few days ago.
Some parts might still be a bit rough around the edges, e. g. there is one mandatory fix which will be part of the next release of Scala (2.10.1) but is not in 2.10.0. If you want to play with it right now, you need to use a nightly build until 2.10.1 is released.
If you encounter any additional issues, please report them!
I may not need it anymore, now that Oracle is making JavaFX open-source on iOS and Android!
EDIT: Oracle updated the article to announce that they will not release a JVM, so it looks like JavaFX+Avian may be the way to go.
Running Java byte code on iOS (not-rooted) is not only running that or those JVM. As far as I understand iOS memory management doesn't allow executable memory pages to be writable in user mode. That basically prohibits any JIT compilation.
So even if it's possible to run some compiled (either from Java or Scala) classes on specific Java VM I would carefully check how this VM supports Ahead-Of-Time compilation in order to be runnable on iOS.
As I have seen Avian AOT works well on a desktop. For iOS you will have to check it yourself, although the project looks promising in AOT area.
I'm trying compile the lastest WebRTC version for iPhone. I not need to compile the entire solution, I only need to compile the VAD module.
To do that, I have created a Xcode project and I have tried to compile the source necessary, but I have a problem with the *.s files and its assembler.
Like in the FFMPEG library, I know that I must "translate" the assembler code to an assembler code that the gcc for iPhone understand, but I don't know how I do this manually.
I have tried to create a configure file and set in it "as=gas-preprocessor.pl" (like in FFMPEG), but does not work.
Any idea? How do I run the gas-preprocessor.pl manually?
Thanks.
I'm just finishing it on iOS and has built standalone static libraries of NS/VAD/AECM and AGC, here's some tips for you, and hope you success:
1. Source File List
for standalone VAD build, you should make sure your project has all of these files(no .s file needed), and I'm not listed the header files here, you will get some header file can not be found errors, just fixing it and things will be done.)
webrtc_vad.c
vad_core.c
vad_filterbank.c
vad_gmm.c
vad_sp.c
real_fft.c
division_operations.c
complex_bit_reverse.c
cross_correlation.c
complex_fft.c
downsample_fast.c
vector_scaling_operations.c
get_scaling_square.c
energy.c
min_max_operations.c
spl_init.c
2. Adding a macro called WEBRTC_MAC
I'm not sure why the Xcode environment does not provide this macro, but it should be defined to ensure that WEBRTC_POSIX is enabled. To define this macro, adding it to a new header file or just define it in the webrtc-header-files.
3. Following these steps to build and setup a static library of WebRTC-VAD module on iOS
notice, do not use LLVM 2.0 to compile the VAD module(use GCC or LLVM GCC). cus' it can throw you lots of errors when compiling some webrtc variable declarations.
4. Using the libwebrtc_vad.a
if you got this far, things are easy to go, just include webrtc_vad.h and using the API provided by this module. and vad is working fine in my case.
hope i helped.
try to check this link https://groups.google.com/forum/?fromgroups=#!topic/discuss-webrtc/VJg-fk2-i_0 i believe you have to set inline assembly correctly. I am also onto this so let me know if you want to switch emails or something.
I am on Linux(Ubuntu) with OpenCV 2.4 installed. I am try to use Eclipse to create an opencv project. When I build the project, I got collect2: ld returned 1 exit status error which I guess is caused by missing libs. Then I put libraries in this project, but I find every lib has three very similar brothers, like:
libopencv_highgui.so
libopencv_highgui.so.2.4
libopencv_highgui.so.2.4.0
So, which one should I add to project libraries? And what's the different between them?
Best Regards.
libopencv_highgui.so and libopencv_highgui.so.2.4 are probably symbolic links to libopencv_highgui.so.2.4.0.
Libraries frequently do this so that software that needs to link against specific versions can while keeping the generic library also exposed.
This is mainly useful when a program to be linked against a major or minor version of a library. Consider if a legacy application needed to link against version 1.2 of libopencv_highgui. The program couldn't link against libopencv_highgui.so because that's not guaranteed to be the correct version. However, the program could link against libopencv_highgui.so.1.2. libopencv_highgui.so.1.2 may be a symbolic link to libopencv_highgui.so.1.2.3, but that would be ok since the third number usually means a minor bug fix that won't break compatibility.
So this brings up which file you should link against. This really depends. Unless you need to depend on some bug or quirk of a specific minor revision, I would definitely avoid linking against the 2.4.0 one. That ties your program specifically to version 2.4.0. When 2.4.1 gets released (or trickles down your distro's package manager), it probably won't break your program.
If you link against libopencv_highgui.so and then 2.5 is installed as the main lib (and then libopencv_highgui.so links to libopencv_highgui.so.2.5.0), there is a chance that your program will not link correctly since the second number does sometimes mean compatibility changes.
So in short, if it's a personal project, just link to whatever you want. libopencv_highgui.so is probably safe if it's personal. If it's going to be distributed, figure out what versions of the library your code will link properly against and then use the vaguest one possible. For example, if your code works with 2.2, 2.3 and 2.4, you should go ahead and link to libopencv_highgui.so. If it only works specifically with 2.4.0, you should link with libopencv_highgui.so.2.4.0. If it will work with any sub revision of 2.4, you should go with libopencv_highgui.so.2.4.
Basically you have to make a choice about what you think will link properly on the most people's setups.
I think I make some mistake here. What I need is these libraries, But when I add them into project libraries. YOU SHOULD USE THESE NAMES, for the library I mentioned in the question, we should add opencv_highgui in to eclipse libraries dependency but libopencv_highgui.so.2.4. For the future use, I write these stuff here.