Difference between using LIB and ar under cygwin - windows

Under cygwin, with libtool I am trying to link a static library. the --mode=link cl.exe line invokes ar cru on the .obj files to create the .lib. However, I know there's another program under windows, LIB. As far as I understand, it's equivalent to ar, but will it make any difference in using ar+ranlib vs. LIB, and how can I force libtool to use LIB instead of ar?

Since setting AR and AR_FLAGS won't work, the only easy solution (that I haven't tried) is CCCL which wraps up cl.exe and link.exe for a neater interface to those programs for autoconf packages. It looks kind of old now, but it might work.
The installation instructions assume that CC/CXX are going to be cl.exe, but you're probably using GCC. In that case, probably AR=cccl needs to be an argument to configure.

Related

Understanding roles of CMake, make and GCC

1. cmake is a command from CMake software: preparation for build automation system; make and make install are commands from Make software: build automation system.
2. From reading this post, what I understand is that:
a. This "cmake and make" stuffs actually use g++ / gcc in its implementation. cmake and make stuffs are basically just tools in using g++ / gcc. Is that correct?
b. gcc / g++ are the compiler that do the actual work.
c. So I can just use gcc / g++ directly without using the make and CMake things?
3. According to this stackoverflow answer: CMake takes a CMakeList.txt file, and outputs it to a platform-specific build format, e.g., a Makefile, Visual Studio, etc.
However when I came across this openCV installation :
mkdir release
cd release
cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local ..
It executes cmake command in a directory where there is no CMakeLists.txt file. Can you explain and elaborate on this?
4. The usual steps that I've seen are: cmake, make, sudo make install.
I read this stackoverflow post, what I understand:
(i) make is for building the project.
(ii) make install is to copy the binary / executables to the installed directories.
a. So when we make, where are the result / binary files / executables stored at?
b. If we only run make without make install, does it mean that the files are not generated?
c. I came across this openCV tutorial on using openCV with GCC and CMake. It uses:
cd <DisplayImage_directory>
cmake .
make
Why doesn't it do make install as well?
5. In summary:
CMake takes CMakeList.txt file (which is cross platform) to generate a Makefile (which is specific to a platform).
I can just write Makefile manually and skip the CMake step. but it is better to do with the CMake step because it is cross platform, otherwise I have to rewrite the Makefile again if I change platform.
Make takes Makefile (which is generated by CMake or written manually) as a guide to compile and build. Make basically uses gcc / g++ or other compiler in its work. Make itself is just a tool for the compiler.
Make install put the result / executables into the install path
CMake generates files for other build systems. These can be Makefiles, Ninja files or projects files for IDEs like Visual Studio or Eclipse. The build files contain calls to compilers like GCC, Clang, or cl.exe. If you have several compilers installed, you can choose one.
All three parts are independent. The compiler, the build system and CMake.
It is easier to understand when you have the history. People used their compiler. Over time they added so many flags, that it was cumbersome to type them every time. So they put the calls in a script. From that the build systems (Make, Ninja) evolved.
The people wanted to support multiple platforms, compilers, scenarios and so on and the build system files became hard to maintain and their use was error-prone. That's the reason people invented meta build system that creates the files for the actual build system. Examples are Autotools or CMake.
Yes
CMake does not use your compiler, make does not implement it, but it calls (uses) the compiler.
The CMakeLists.txt file should be in the parent directory of release. The last argument of the CMake call indicates the path where the CMakeLists.txt file is located.
Right, make generates the file in the build directory. In your example from 3. release is the build directory. You can find all the generated files and use them. Installing is optional, especially if you want to develop the software, you are not installing it.
Try writing Makefiles for a large project and you will see how much work it is. But yes, everything in 5 is right.

gcc dll - compiled under Linux

I have a project written in gcc - bison -flex on Linux environment. All the project is implemented into a *.so file and is called from python-tkinter graphic surface.
There is a need to run it on windows. However I'd avoid to install all the windows equivalent of gcc - bison -flex programs.
Is it possible to force gcc IN LINUX ENVIRONMENT to compile WINDOWS DLL instead of *.so? It could make life easier to use the same technics as I do now: just do calls from python-tkinter graphic surface.
You can, of course, cross-compile it.
You'll need some packages installed, though.
Your normal project would be able to build if you use the MINGW equivalent of GCC for the target architecture.
Also, take a look at this:
Manual for cross-compiling a C++ application from Linux to Windows?
The linking can be kind of troublesome though, since it could come a time where softlinking fails due to versions. In that case you'll need to create some symbolic links to the correct version.
The output of the compilation process should be with -o DYNAMIC-LIBRARIE-NAME.dll and of course use the -shared flag.
Hope it gives you some pointers..
Regards.

Proper way to upgrade from llvm-g++-4.2 to g++-4.7 on Mac

I have Lion 10.7.3 with the Command-line tool installed. I wanted to experiment with C++11, so I used homebrew to install GCC 4.7 as documented here.
How can I now upgrade the /usr/bin/g++ to be the one installed by Homebrew? Is it as simple as symlinking it? I just want to double check and make sure. Thanks!
First, are you sure you need g++ 4.7? As you can see from the C++11 implementation status page, recent versions of clang support most of C++11 too. Of course there are still things that g++ handles and clang doesn't, but there are also still things that clang supports and g++ doesn't. And, more importantly, you already have a recent version of clang, from Apple, configured and ready to go, as your default compiler. Plus, g++ after 4.2 doesn't support Mac extensions like, say, -arch, which means you can't use it to build a whole lot of third-party software (because most configure scripts assume that if you're on a Mac, your compiler supports Mac extensions).
But if you want g++ 4.7, you can do it. Just not by trying to replace /usr/bin/g++ with a different version. Never replace anything in /usr/bin (or /System) with non-Apple stuff except in a few very rare cases (when you have a strong reassurance from someone who knows what they're talking about).
A better thing to do is to just install another compiler in parallel. Just let Homebrew install its favorite way (so it installs into some prefix like /usr/local/Cellar/gcc/4.7, then symlinks all the appropriate stuff into /usr/local/bin, etc.), and use it that way.
When compiling your code, instead of writing g++, write /usr/local/bin/g++, or g++-4.7.
If you get tired of doing that, put /usr/local/bin higher on your PATH that /usr/bin, or create a shell alias, or stick it in the environment variable CXX and write $CXX instead of g++.
If you're using a GUI IDE, you should be able to configure it to use your compiler by setting the path to it somewhere. (Unless you're using Xcode, which you can only configure to work with Apple-tested compilers.)
This is all you need for experimenting with your own code. If you want to compile third-party applications with this compiler, that may be a bit more complicated. You don't often actually compile each source file and link the result together; you just do configure && make and let them do the heavy lifting for you.
Fortunately, most packages will respect the standard environment variables, especially CXX for specifying a default C++ compiler and CC for a default C compiler. (That's why I suggested the name CXX above.)
Just remember that, again, g++ 4.7 doesn't support Mac extensions, so if you're not prepared to debug a bunch of autoconf-based configure scripts complaining that your compiler can't generate code because it assumed it could throw -arch x86_64 at any compiler on a Mac, etc., don't do this.

Use headers and libraries from different folders

I have two GTK builds on my Mac, an X11 one with headers and a Quartz one without. I can compile Vala code for X11 just fine, but how do I use the Quartz libraries?
This is probably a C question, but I only ever used that toolchain through valac.
When using valac, it gets the appropriate compile and link flags from pkg-config based on the --pkg flags. You can see what is being included with pkg-config --cflags --libs gtk+-2.0. If you wish to change this you have two opions:
Use valac -C to only produce C files and manage the compilation and linking yourself.
Set export PKG_CONFIG_PATH=/usr/lib/pkgconfig:/sw/lib/pkgconfig or whatever collection of directories to get your packages coming in the desired order.
I'm not quite sure where your GTK+ installs are located, presumably in a MacPorts tree.

How to statically compile an SDL game on Windows

I have been trying to produce a statically linked "single binary" version of my game for windows. I want to link with sdl, sdl_image and sdl_mixer which in turn pull in a few support libraries. Unfortunately I haven't found a way to get them all to compile and link using cygwin/mingw/gcc. As far as I can tell all existing public versions are only shared libraries / dlls.
Please note that I'm not talking about licencing here. The source will be open thus the GPL/LGPLness of sdl is not relevant.
When compiling your project, you need to make just a couple changes to your makefile.
Instead of sdl-config --libs, use sdl-config --static-libs
Surround the use of the above-mentioned sdl-config --static-libs with -Wl,-Bstatic and -Wl,-Bdynamic. This tells GCC to force static linking, but only for the libraries specified between them.
If your makefile currently looks like:
SDLLIBS=`sdl-config --libs`
Change it to:
SDLLIBS=-Wl,-Bstatic `sdl-config --static-libs` -Wl,-Bdynamic
These are actually the same things you should do on Unix-like systems, but it usually doesn't cause as many errors on Unix-likes if you use the simpler -static flag to GCC, like it does on Windows.
Via this SDL mailing list post it seems that the sdl development tools ship with a sdl-config script that you can use with the --static-libs flag to determine what linker flags you need to use.
Environment: VMWare Virtual Machine with Windows 7 x64 and Equipment we Dev c + + build 7.4.2.569, complilador g+ + (tdm-1) 4.6.1
Once, SDL2-2.0.3 API installed as configuration Dev c ++ is not very clear what I've done as tradition requires command line.
The first problem is that Windows 7 appears to have changed the methodology and they go to his ball. Inventory. Ref. https://stackoverflow.com/users/464581/cheers-and-hth-alf
After the first hurdle, SDL_platform.h is that bad, it's down another, I do not remember where I downloaded, but the next does not work in the indicated version.
We must put SDL2.h ls in the directory of the executable.
D:\prg_desa\zsdl2>g++ bar.cpp main.cpp -o pepe1 -ID:\SDL2-2.0.3\i686-w64-mingw32\include\SDL2 -LD:\SDL2-2.0.3\i686-w64-mingw32\lib -lmingw32 -lSDL2main -lSDL2 -mwindow
I've finally compiled and works SDL2 testing.
That's because the SDL libs are under the LGPL-license.
If you want to static link the libs (you can do that if your recompile them. It needs some hacking into the makefiles though) you have to place your game under some compatible open source license as well.
The SDL-libs come as shared libraries because most programs that use them are closed source. The binary distribution comes in a form that most people need.
On my system (Ubuntu) I have to use the following flags:
-Wl,Bstatic -lSDL_image `sdl-config --libs` -lpng12 -lz -ltiff -ljpeg -lasound -laudio -lesd -Wl,-Bdynamic `directfb-config --libs` -lpulse-simple -lcaca -laa -ldl
That links SDL, SDL_image, and many of their dependencies as static. libdl you never want static, so making a fully-static binary that uses SDL_image is a poor idea. pulse,caca,aa, and directfb can probably be made static. I haven't got far enough to figure them out yet.

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