I'm having trouble linking my program to a library. I've never done this before so I'm probably doing something stupid, but as far as I can tell I'm doing the right thing. I need to link my program foo.f90 to a library libbar.a which is in a directory elsewhere below my home directory. I enter the command:
gfortran -c foo.f90
gfortran -o foo foo.f90 -L/directory/of/library -llibbar.a
But this throws:
ld: library not found for -llibhealpix.a
Where of course libhealpix.a is the real library (rather than libbar.a)
Any ideas as to why this would occur?
Try -lbar (or perhaps -lhealpix, if that's the real library name).
-lxyz results in a search for a file named libxyz.a. Consequently, if you specify -llibbar.a then the file needs to be named liblibbar.a.a.
You could also simply specify the path and full name of the archive file on the gfortran command line: gfortran -o foo foo.f90 /directory/of/library/libbar.a
Related
The book Advanced Linux Programming contains:
The system searches only /lib and /usr/lib, by default. If a shared library that is linked into your program is installed outside those directories, it will not be found, and the system will refuse to run the program.
One solution to this problem is to use the -Wl, -rpath option when linking the program. Another solution to this problem is to set the LD_LIBRARY_PATH environment variable when running the program.
So from information above, I assume adding path to $LD_LIBRARY_PATH is equivalent to passing argument to linker when compiling something like -Wl,-rpath,SOME_PATH until I hit this problem:
I am trying to generate a shared library and this shared library depends on some .so files somewhere at my system. Here's the command for compilation:
g++ -fPIC -shared -Wl,-soname,libA.so -o libA.so SRC.cpp -L PATH_A -I PATH_B -Wl,-rpath,PATH_C:PATH_D:PATH_E -la -lb -lc
After I compile, I use ldd to check if there's any dependency issue and something unexpected to me happens:
Some of dependency are found and some of them are not (libA.so => not found), however all the paths it needs (PATH_C PATH_DPATH_E) have been passed to argument -Wl,-rpath.
So it seems -Wl,-rpath does not work for this case , the only solution to make it work is to add the path to libA.so to $LD_LIBRARY_PATH and ldd returns that all the dependency are found.
I would like to know why -Wl,-rpath fails in, what's the difference between adding the path to $LD_LIBRARY_PATH and passing an argument to -Wl,-rpath?
Good Day Everyone,
N.B - This problem has been solved - I have provided my own solution in the answer section however the solution provided by Jonathan is much shorter. Nevertheless, this was the following question I originally posted:
I am basically trying to compile a serial library (for UART communication) on Linux however I am not really sure how to correctly compile (I have mentioned what I have done so far below), any suggestions would be highly valuable. I am using the serialib library - which is composed of 2 main files (serialib.h and serialib.cpp) , you may directly view the source code of these files here (scroll all the way to the bottom and view the files in new tabs): http://serialib.free.fr/html/classserialib.html
I transferred these files (serialib.h and serialib.cpp) to my BeagleBone Black micro-controller which is running Debian (Wheezy) , g++/gcc (Debian 4.6.3-14) 4.6.3. I wrote my own program (uart.cpp is my file name) to access the functions provided by this library, this is what I wrote:
#include <iostream>
#include "serialib.h"
#ifdef __linux__
#define DEVICE_PORT "/dev/ttyO1"
#endif
int main()
{
serialib LS;
return 0;
}
So as you can see I am trying to access the 'seriallib' class. serialib.h, serialib.cpp and uart.cpp are all in the home directory. I also manually added the iostream library in serialib.cpp as I did not see it being declared in the original source code.
Now I am really unsure of how to compile such external libraries but so far I tried the following steps:
g++ -c -Wall -Werror -fPIC serialib.c to convert to PIC which gives the following error:
distcc[3142] (dcc_parse_hosts) Warning: /home/debian/.distcc/zeroconf/hosts contained no hosts; can't distribute work
distcc[3142] (dcc_zeroconf_add_hosts) CRITICAL! failed to parse host file.
distcc[3142] (dcc_build_somewhere) Warning: failed to distribute, running locally instead
g++ serialib.cpp -L /home/debian/serialib.h which gives the following error:
/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../arm-linux-gnueabihf/crt1.o: In function _start':
(.text+0x30): undefined reference tomain'
collect2: ld returned 1 exit status
distcc[3210] ERROR: compile serialib.cpp on localhost failed
As of now I am still finding out how to compile this and if I manage to work this out then I'll post my solution here too. Once again any suggestion will be highly valuable. Thank you all :) .
g++ -c -Wall -Werror -fPIC serialib.c to convert to PIC which gives the following error:
The "error" is not an error, it's a warning, telling you that your distcc setup is broken, but that it compiled locally.
That command doesn't "convert to PIC", it compiles the file serialib.c and produces a compiled object file, serialib.o
g++ serialib.cpp -L /home/debian/serialib.h
This is just nonsense. It tries to build a program from serialib.cpp and use the directory /home/debian/serialib.h (which isn't a directory!) to find libraries.
You don't need to "compile a library" you can just compile both the source files and link them together into a program. Either:
g++ -c serialib.cpp
g++ -c uart.cpp
g++ serialib.o uart.o -o uart
Or all in one command:
g++ serialib.cpp uart.cpp -o uart
You should read An Introduction to GCC to understand the commands, not just enter bogus commands without understanding them.
I have found a solution to this problem, hope this helps for all the future readers with similar problems. I have my own source code uart.cpp (Given in the question) which I want to compile, the external library is serialib that contains two main files (serialib.h and serialib.cpp), you will want to replace the following commands with respect to the files you have
Step 1: Compiling with position independent code
g++ -c -Wall -Werror -fpic serialib.cpp
Step 2: Creating a shared library
g++ -shared -o libserialib.so serialib.o , here the library is libserialib.so.
Step 3: Linking your source code with library
g++ -L /home/debian -lserialib uart.cpp -o uart
g++ -L /home/debian -Wall -o test uart.cpp -lserialib
You may save the library at a different path and you may have a different name of course. Suppose you have a library called libabc.so at the directory /home/user/myDir then the commands will be like:
g++ -L /home/user/myDir -labc your_code.cpp -o your_code
g++ -L /home/user/myDir -Wall -o test your_code.cpp -labc
test is out own program, lserialib is actually looking for libserialib.so and not serialib.o as gcc/g++ assumes all libraries start with lib and end with .so or .a and you can see the same goes for labc as it will look for libabc.so thus it is important to make sure your library name begins with lib and ends with .so or .a
Step 4: Making library available at run time
Here we provide the path where the library is actually stored, I saved it in the directory /home/debian which is why my command looks like:
export LD_LIBRARY_PATH=/home/debian:$LD_LIBRARY_PATH
if your library is saved at /path/to/file then the command will look like:
export LD_LIBRARY_PATH=/path/to/file:$LD_LIBRARY_PATH
This is to help the loader find the shared library and to view this path: echo $LD_LIBRARY_PATH and to unset this: unset LD_LIBRARY_PATH
To execute the program type either ./test or ./uart and in case of any modification to the main source code (uart.cpp in this case) , simply repeat step 3. I found the following link very useful: http://www.cprogramming.com/tutorial/shared-libraries-linux-gcc.html . Thank you to all of you who took time to read this question and especially those who gave me suggestions. If anyone has more or better solutions, feel free to post them here to assist future readers :).
I use MinGW32 more specifically TDM-GCC-32. I have very simple project I link to one custom library but this error pops out:
>g++ -D_WIN32 -D_MINGW -lgdi32 -lgdiplus -Linterception/x86 -linterception main.cpp -o interceptor.exe
interception/x86/libinterception.a(dgnes00125.o):(.text+0x0): multiple definitio
n of `atexit'
C:/TDM-GCC-32/bin/../lib/gcc/mingw32/5.1.0/../../../crt2.o:crt1.c:(.text+0x2c0):
first defined here
interception/x86/libinterception.a(dgnes00109.o):(.text+0x0): multiple definitio
n of `_onexit'
C:/TDM-GCC-32/bin/../lib/gcc/mingw32/5.1.0/../../../crt2.o:crt1.c:(.text+0x2d0):
first defined here
C:/TDM-GCC-32/bin/../lib/gcc/mingw32/5.1.0/../../../../mingw32/bin/ld.exe: C:/TD
M-GCC-32/bin/../lib/gcc/mingw32/5.1.0/../../../crt2.o: bad reloc address 0x20 in
section `.eh_frame'
collect2.exe: error: ld returned 1 exit status
Commands I use to build the library:
gcc -DINTERCEPTION_EXPORT -D_WIN32 -D_MINGW -shared -o interception.dll interception.c
dlltool -z interception.def --export-all-symbol interception.dll
dlltool -d interception.def -l libinterception.a
I guess I have to use different options for compiling the library to avoid redefinitions..
The dlltool method I believe is currently deprecated. I can't fault you here though, as most of the available documentation still says to do it this way.
Gcc will link directly against .dll files, making .a files obsolete (at least for dealing with dll's - the only current reason to use a .a file is for static linking). You don't even have to specify the dll with the -l flag, although you have to specify the path of the dll if it's not in your current directory
C:\Users\burito>gcc main.o opengl32.dll -o main.exe
gcc: error: opengl32.dll: No such file or directory
C:\Users\burito>gcc main.o c:\Windows\system32\opengl32.dll -o main.exe
C:\Users\burito>
Ok, opengl32.dll is perhaps not a great example, but I hope I've given you the general idea.
I believe MSVC still needs its .lib files to use a .dll, for which there are several ways of making them if the library doesn't come with one.
In your specific case, the command that should work would be...
g++ -D_WIN32 -D_MINGW -lgdi32 -lgdiplus interception/x86/interception.dll main.cpp -o interceptor.exe
If for whatever reason you really do need to create a .a file from a .dll, the command that has worked for me is...
gendef interception.dll
dlltool -l interception.a -d interception.def -k -A
As the repository you linked does provide .dll files in its releases, you shouldn't have to build them yourself
I am trying to generate a c++ library using the g++ compiler. My library has another C library as dependency and I have compiled it in order to obtain the .so files.
I have the following structure:
src:
include/linux:
libcustom.a
libcustom.la
libcustom.so
libcustom.so.0
libcustom.so.0.0.0
Now, when I have all the .o files of my cpp classes, and I want to link the library, I execute the following command:
g++ -shared -L/usr/lib/R/lib -Wl,-Bsymbolic-functions -Wl,-z,relro -o mylibrary.so File1.o File2.o File3.o -L./include/linux -lc++ -lutil -lm -lcustom -Wl,-rpath='$ORIGIN/include/linux' -L/usr/lib/R/lib -lR
But it throws me the error:
libcustom.so.0: cannot open shared object file: No such file or directory
I am executing the command from the src directory.
I know it could be fixed editing the LD_LIBRARY_PATH, but the idea it is someone can use my library without the need of configuring anything, so I am trying to do that with the c++'s -rpath flag.
Any idea how can I fix it, or the reason for the error?
The error message you got seems to come from the run-time loader ld.so instead of the linker ld (I know the names are confusing). You have to distinguish between finding so's at link-time and at run-time. The -L flag you give at link-time has nothing to do with localizing the library at run-time.
Your rpath=./include/linux value is not correct, because dot is not recognized by the ld as relative path. Relative searching path should be given like
-Wl,-rpath='$ORIGIN/include/linux'
where the $ORIGIN represents the folder where your executable (not mylibrary.so) locates. Make sure to use single quote and not double quote because the string $ORIGIN should be passed to the linker literally and hard coded into the executable file.
More details goes
how to link to shared lib from shared lib with relative path
ld: Using -rpath,$ORIGIN inside a shared library (recursive)
I am trying to compile a project that depends on the Xerces XML Parser. The project compiles for Windows without any difficulty, but I'm having some trouble compiling it with g++ in Cygwin.
In order to use Xerces, I am trying to compile my code against the static library libxerces-c.a. But when I do so, I get errors that look like this:
/tmp/cc2QGvMh.o:test.cpp:(.text+0x3a): undefined reference to `xercesc_2_8::DOMImplementationRegistry::getDOMImplementation(unsigned short const*)'
I've inspected the static library using ar, and confirmed that it contains the DOMImplementationRegistry.o file that defines the function that I am calling.
ar -t libxerces-c.a
...
DOMImplementationImpl.o
DOMImplementationRegistry.o
DOMLocatorImpl.o
...
I've also extracted the object files from the library, and used 'nm' to make sure that the function I am calling actually exists:
ar -x libxerces-c.a
nm --demangle DOMImplementationRegistry.o
...
00000080 T xercesc_2_8::getDOMImplSrcVectorMutex()
00000300 T xercesc_2_8::DOMImplementationRegistry::getDOMImplementation(unsigned short const*)
000002a0 T xercesc_2_8::DOMImplementationRegistry::addSource(xercesc_2_8::DOMImplementationSource*)
...
Since I can compile everything for Windows but not with g++, I thought that the error could be in the linker order (similar to the problem described in this question). However, even after changing the linker order, I am still getting the same compiler error. I have tried both
g++ -o test.exe test.cpp -Llib -lxerces-c
and
g++ -o test.exe test.cpp lib/libxerces-c.a
Any ideas?
Your project uses method from xercesc_2_6 namespace as pointed by compiler error message but your library offers xercesc_2_8 version. Problem is probably caused by mismatch between headers you use and library object file.
You didn't say the source of the archive. If it isn't compiled with cygwin, it could be a name mangling problem. Compiling the library from source might well fix this.
It could also be that the archive is built incorrectly so that it has internal resolution problems. Try giving the library name twice.
g++ -o test.exe test.cpp lib/libxerces-c.a lib/libxerces-c.a
If this works, the archive is broken and you should look for or build a new one.
Try the linker option --enable-stdcall-fixup (see 'man ld'). It will care for name mangling and calling conventions:
g++ -o test.exe test.o -Wl,--enable-stdcall-fixup -Llib -lxerces-c