I'm trying to open a dynamic library file (.so) using dlopen().
So I created libhello.so file in Linux using gcc and compiled the main.c file with --preload-file libhello.so option.
However, I got the following error in a browser:
(index):29 To use dlopen, you need to use Emscripten's linking support, see https://github.com/emscripten-core/emscripten/wiki/Linking
Should I compile .so file using emcc instead of gcc in order to be used in a web browser?
reference: https://emscripten.org/docs/porting/files/packaging_files.html#preloading-files
Related
I am using gcc 8.1.0 on Windows. To install it I set up Code::Blocks on my computer and updated the environment variable list by adding the path to the gcc.exe program within the installation folder of CodeBlocks. The file editor I used was the built-in editor in Visual Studio. The terminal to compile was the power shell from Visual Studio as well.
In the library development folder I have the files mul.c and mul.h. Their content is irrelevant.
To compile the library I use the command:
gcc -c mul.c
When I run it, it creates a file object mul.o and not mul.lib. I needed to use the option -o mul.lib to successfully create the desired extension file. After placing the header, the .lib file and the main.c in the same parent folder I am obvioudly able to build the executable by running.
gcc main.c -I./include -L/static -lmul -o my_program.exe
I have two questions:
Why does gcc produces a .o if I am in a Windows environment?
I followed a tutorial that compile the static library under Linux and it names it libmul.o, in this way the -lmul option is able to retrieve the library. But if I call my generated static library libul.lib it generates the error:
C:/Program Files/CodeBlocks/MinGW/bin/../lib/gcc/x86_64-w64-ingw32/8.1.0/../../../../x86_64-w64-mingw32/bin/ld.exe: cannot find -lmul
collect2.exe: error: ld returned 1 exit status
Are these a normal behaviours by gcc, or is it side effect of making gcc available just by updating the Windows environmental variables list?
Thank you to the community in advance.
GCC comes from the *nix world where libraries have the .a extension. When using GCC+MinGW this remains the case.
Shared libraries in MinGW are .dll files but their libraries for linking are .dll.a files.
The advantage of .a files is that a lot of sources build out of the box on Windows with MinGW, especially when using MSYS2 shell.
If you use -l it will look for .a (or .dll.a for shared build) file adding the lib prefix and the extension automatically.
So -lmul will look for libmul.a (static, e.g. when --static linker flag is given) or libmul.dll.a (shared).
By the way, you are using quite an old GCC 8.1.0.
As I write this current version is 12.2.0. Check https://winlibs.com/ for a standalone download (instructions on how to configure in Code::Blocks are on the site) or use MSYS2's package manager pacman.
I have a shared library (*.so) created using Real View Compiler Tools (RVCT 3.2) on windows target. Then I try to link this *.so file with my application using gcc on linux system.
What is the gcc option to link this shared library with my application linux?
My question is, is the -shared option, which is used as
gcc -shared myfile.so
..., used to create the SO file or to link the SO file? I believe it creates something like:
gcc -lmyfile.so
Is this enough? Or is there any other switch to tell the linker that it's a dynamic library (shared object)?
What worked for me was:
gcc -L. -l:myfile.so
gcc -lmyfile should be enough (provided that your library is named libmyfile.so). The linker searches for shared objects when possible and AFAIK prefers them.
I have a JNI project, which I have to make work on Windows (I am working on Linux). This project actually depends on third-party library file which is static (archived i.e .a files). I am trying to create a JNI shared library file using i686-w64-mingw32-g++ and including -static followed by static third-party library name. Following is the command I am using
i686-w64-mingw32-g++ -v -L./ -L/home/user/jre1.8.0_40/lib/amd64/ -I/user/all/apps/Linux2/x86_64/gcc/4.8.2/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.8.2/include -shared -o test.dll test.cpp -lstdc++ -static -thirdparty
In-spite of placing the third party library in the current working directory, I keep getting error
/user/all/apps/Linux2/src/mxe/2013_12_03/usr/bin/../lib/gcc/i686-w64-mingw32/4.8.1/../../../../i686-w64-mingw32/bin/ld: cannot find -thirdparty
Please note : I included -I/user/all/apps/Linux2/x86_64/gcc/4.8.2/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.8.2/include to avoid the error cannot find jni.h which I hit before including the path.
I also tried to compile using gcc, in place of g++.
Do I need to create .dll of this third-party library(currently it is archived .a containing .obj files)?
Being a newbie in cross compilers, I might be doing something wrong. Please correct me and any suggestions with this will be very helpful. Thank you.
-Wl,--export-all-symbols -Wl,--add-stdcall-alias -v adding this solved my problem
I'm trying to play an mp3 file in terminal using C and I followed this link to do so.
I've installed the two libraries libmpg123 and libao. Also, I've compiled the play.c program using the command:
gcc -O2 -o play play.c -lmpg123 -lao
But I get the following error when I run it:
./play: error while loading shared libraries: libao.so.4: cannot open shared object file: No such file or directory
Can you figure it out why it happened.
The executable can be linked, but at run-time, it cannot find the shared libraries. Add the libraries to your LD_LIBRARY_PATH so the program can find them at run time.
I'm Linux rookie and I'm trying to move my library from windows to Linux. It is native binary (mylib.so), but it will be loaded by mono ( [DllImport()] ). I'm using a pcre (Perl Compatible Regular Expressions) in this library. When my .NET executable tries to load mylib.so it throws exception (lib not found). When I set MONO_LOG_LEVEL=debug. I says that my library is found, but pcre library is not.
I've tried to to load it dynamically (dlopen(), dlsym()). When I build executable version of my library linking it with dl (-ldl) it works fine. But when I load it from mono I got SIGSEGV.
I create this library like (for version with dl):
g++ -fPIC -c *.cpp
g++ -shared -Wl,-soname,libmylib.so.1.1 -ldl -o libmylib.so.1.1 *.o
I've create simple test program that link against mylib.so and dl (-l:libmylib.so.1.1 -ldl) and it works.
I think I need to force mylib to link with dl (or directly with pcre), but I don't know how. (I hope it's possible)
All what I want is to create library that use pcre and work under mono.
You incorrectly linked your library: if it uses libpcre you must link it, too, with the -lpcre option.