I am using Ubuntu and my IDE is Aptana 3.0
I am getting the following error when trying to build. The library libfcgi.a is located in /usr/local/lib/.
In the Library C++ Linker section of the project properties, I added /usr/local/lib/ to the search path and the file /usr/local/lib/libfcgi.a.
Why can I still not build?
**** Build of configuration Debug for project rtb ****
make all
Building target: rtb
Invoking: GCC C++ Linker
g++ -L/usr/local/lib -o"rtb" ./src/rtb.o -l/usr/local/lib/libfcgi.a
/usr/bin/ld: cannot find -l/usr/local/lib/libfcgi.a
collect2: ld returned 1 exit status
make: *** [rtb] Error 1
I think this may be what you want;
g++ -L/usr/local/lib -o "rtb" ./src/rtb.o -lfcgi
-l<value> will automatically look in all folders listed with -L for a library named lib<value>.a or lib<value>.so, all you need is the '-lfcgi'.
Try "-lfcgi" instead
g++ -L/usr/local/lib -o"rtb" ./src/rtb.o -lfcgi
Your linker flag is wrong it needs to be -lfcgi and not the whole path with the "lib" prefix and the .a suffix.
You can change it by hand, or in Apatana. To do so you don't have to give him the full qualified path to your lib two times. ( You already gave him the search path, remember? ). Usually you define additional libraries just like this:
cfgi and your IDE does the rest to add it to the linker flags!
You should do
g++ -o "rtb" ./src/rtb.o -lfcgi
In the unlikely case that /usr/local/lib/ is not in your search path, you can either add that path in the command line like
g++ -L/usr/local/lib -o "rtb" ./src/rtb.o -lfcgi
or put it in the environment variable LIBRARY_PATH before calling your compile command, e.g. with bash:
if [ -z "$LIBRARY_PATH" ];
then export LIBRARY_PATH=/usr/local/lib;
else export LIBRARY_PATH="$LIBRARY_PATH":/usr/local/lib;
fi
If you insist in giving the explicit file name, omit the -l:
g++ -L/usr/local/lib -o "rtb" ./src/rtb.o /usr/local/lib/libfcgi.a
However I'd advise against that because it's inflexible. If the issue is that there's another, incompatible version of the library installed, it's better to make sure that the correct one comes first in the search path (or even better, make sure that the wrong one isn't in the search path at all ― maybe even by removing it from the system).
That's for the help all....really appreciate it.
Here is the solution. I had to use -lfcgi++ and I added the
g++ -L/usr/local/include/ -lfcgi++ -o"rtb" ./src/rtb.o
The above was the output from aptanta console. I tried -lfcgi and did not work. Google search lead to using -lfcgi++.
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?
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 have some basic questions regarding linking against a C/C++ library. I am trying to understand the difference in using the two different usages -L/usr/local/lib -lm usage and /usr/local/lib/libm.a usage. E.g., when I compile and link an example from the [SUNDIALS] library, both of the following work
gcc -Wall cvRoberts_dns.c -o cvRoberts_dns.exe -I/usr/local/include -L/usr/local/lib/ -lsundials_cvode -lsundials_nvecserial -lm
OR
gcc -Wall cvRoberts_dns.c -o cvRoberts_dns.exe /usr/local/lib/libsundials_cvode.a /usr/local/lib/libsundials_nvecserial.a
However, to compile and link an example from the library [libsbml], the following works
g++ -Wall readSBML.cpp -o readSBML.exe -I/usr/local/include -L/usr/local/lib -lsbml
but the this does not
g++ -Wall readSBML.cpp -o readSBML.exe /usr/local/lib/libsbml.a
If required, I can post the complete error message I get, but the last line of the message is as follows
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
My questions are as follows:
In the second style of linking (of the first example), there is no information regarding where to find the include files (header files), how does the compiler know the information supplied in -I/usr/local/include which is provided in the first style of the first example?
In the second style of first example there is no /usr/local/lib/libm.a (it actually gives an error message that libm.a cannot be found if I try to include it), then why -lm is required in the first style?
How do I compile the second example in the second style (i.e., using /usr/local/lib/libsbml.a)? I do see that there are files - libsbml.a and libsbml-static.a in the /usr/local/lib folder, but none of them work.
If it helps, I am on an OS X machine.
I would be very thankful if any one could help in this regard.
Just an update - I tried
g++ -Wall readSBML.cpp -o readSBML.exe /usr/local/lib/libsbml.5.dylib
and that compiled and linked just fine.
Thanks
SN
In general
The -L option is meant to find where the libraries themselves are. Each library is a collection of one or more object code (machine language) files. There is no need to find the include files.
The -I option has nothing to with linker, it helps the compiler resolve the header files used in your driver programme( eg Roberts_dns.c). This happens during the pre-processing stage.
In the second style of linking (of the first example), there is no
information regarding where to find the include files (header files),..
If the compilation worked as you expected,it may be because /usr/local/include is in the default include path for gcc. To check the default include path for gcc do gcc -xc -E -v -.
In the second style of first example there is no
/usr/local/lib/libm.a(it actually gives an error message that libm.a
cannot be found if I try to include it), then why -lm is required in
the first style?
In Linux, some libraries like libc.a are directly linked to your execultable by default while libm.a is not. In Mac (your environment), though, libm is directly link to the executable by default. So you don't have to explicitly link it. It is less likely that libm.a is located in /usr/local/lib/. So you got an error. But why link it in the first place?
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 have written a few programs and while trying to compile them using g++,as thus,
$ g++ minIni.c device_datum.cpp fanuc_axis.cpp fanuc_path.cpp service.cpp condition.cpp cutting_tool.cpp string_buffer.cpp logger.cpp client.cpp server.cpp adapter.cpp fanuc_adapter.cpp FanucAdapter.cpp -L/usr/local/lib/ -lfwlib32 -lpthread -o adapter
I keep getting the following error:
/usr/bin/ld: cannot find -lfwlib32
collect2: error: ld returned 1 exit status
fwlib32.h is the library I am trying to include. The shared object file libfwlib32.so is present in /usr/local/lib as well as /usr/lib. But I am unable link to it. I have tried all the solutions offered by similar questions including
$ export LIBRARY_PATH=/usr/local/lib/
$ export LD_LIBRARY_PATH=/usr/local/lib
I have done the above for /usr/lib as well, but still the same error.
I have tried using the -L option in the command line but I still get the error.
I even created a new folder called lib, pasted libfwlib32.so.1.0.1 into it and ran
$ ln -s ~/lib/libfwlib32.so.1.0.1 ~/lib/libfwlib32.so
on the console to create a new .so file and gave ~/lib as argument to -L option on the command line. It made no difference. I am at the point of tearing my hair out so any help will be appreciated.
Thanks alot!
You should put -l option in the very last as:
$ g++ minIni.c device_datum.cpp fanuc_axis.cpp fanuc_path.cpp service.cpp condition.cpp cutting_tool.cpp string_buffer.cpp logger.cpp client.cpp server.cpp adapter.cpp fanuc_adapter.cpp FanucAdapter.cpp -L/usr/local/lib/ -o adapter -lfwlib32 -lpthread
Note: Please make sure that all the header and source file are in the same folder.
Note that specifying -L~/lib won't work as the ~ will not be expanded by the shell. Also you can't add a space between -L and ~/lib. Instead you must specify it as a relative or absolute path.
Have you checked that the libfwlib32.so symlink exists in /usr/local/lib (or /usr/lib) in addition to the libfwlib32.so.1.0.1 file?
Another possibility is that the library is the wrong architecture (ie. 32-bit while your system is 64-bit), but then ld should print a message about skipping incompatible library. You can check the architecture of the library by running 'file libfwlib32.so.1.0.1'.
The error message suggests that -lfwlib32 is being interpreted as a filename not as a -l parameter. Put all the parameters before the files to be compiled
g++ -m32 -L/usr/local/lib/ -lfwlib32 -lpthread -o adapter minIni.c device_datum.cpp fanuc_axis.cpp fanuc_path.cpp service.cpp condition.cpp cutting_tool.cpp string_buffer.cpp logger.cpp client.cpp server.cpp adapter.cpp fanuc_adapter.cpp FanucAdapter.cpp
As has been pointed out by #Erik Johannessen, libfwlib32.so is a 32bit library, so you need to add -m32 to build a 32bit executable.