Two libraries I use in my application both use zlib, which causes a conflict when linking my project. I want to compile these libraries without zlib; I want to statically link the zlib library in my own project and have this libraries use that instead. How can I do that?
If both libraries are statically linked to the executable and zlib is also statically linked to the executable, then you just build the two libraries without linking them against zlib and add zlib to the linker dependencies when building the executable.
If both libraries are DLLs then you need to check why you're exporting the zlib symbols from them - normally you should be able to just link two DLLs to an executable with both DLLs using overlapping dependencies and not run into an issues from the overlapping dependencies.
Related
My library has minimal, straightforward CMake code with the pertinent lines
add_library(MyLib <sources>)
install(
TARGETS MyLib
LIBRARY DESTINATION ${destination}/lib
RUNTIME DESTINATION ${destination}/lib
COMPONENT Libraries)
install(
FILES mylib.h
DESTINATION ${destination}/include
COMPONENT Headers)
When executed under Windows, the system generates mylib.dll in ...\build\Release, and mylib.lib and mylib.exp (what's that?) in ...\build\lib\Release. It only installs mylib.dll.
My application has minimal, straightforward CMake code to search for my library:
find_path(MyLib_INCLUDE_DIR mylib.h)
find_library(MyLib_LIBRARIES NAMES MyLib)
include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(MyLib DEFAULT_MSG MyLib_LIBRARIES MyLib_INCLUDE_DIR)
Which works under Linux, but under Windows results in
-- Could NOT find MyLib (missing: MyLib_LIBRARIES)
From experimentation I know that this error occurs whenever there is only a .DLL file, and no associated .LIB import library.
Shall I correct MyLib to install mylib.lib? How?
Or is it possible to modify my application so that it is satisfied with mylib.dll only? How?
Research done so far
This is not about static vs dynamic linking (DLL and LIB files - what and why?, cmake link against dll/lib): I want dynamic linking; if a .LIB file is required, it has nothing to do with static linking.
This link cmake : shared library : how to get the .lib name instead of .dll name? may be pertinent, but is not explicit enough. Two other questions CMake generated VS project expecting lib instead of dll, Linking dll/lib to a cmake project seem related, but have no answer.
Command install classifies .lib file for a shared library as ARCHIVE. This is explicitly stated in the documentation:
For DLL platforms (all Windows-based systems including Cygwin), the DLL import library is treated as an ARCHIVE target.
So you need to add ARCHIVE clause to install() for install .lib file as well:
install(
TARGETS MyLib
ARCHIVE DESTINATION ${destination}/lib
LIBRARY DESTINATION ${destination}/lib
RUNTIME DESTINATION ${destination}/bin
COMPONENT Libraries)
Not also, that RUNTIME DESTINATION is usually specified as bin, the same as destination for executables. This helps the executables on Windows to locate the shared libraries (.dll).
I've installed the Nana library and I've read from their website that the library needs some shared libraries to work.. So during linking (gcc) i need to put all links (-lXft, -l...).
Is there a solution to auto link shared libraries needed by Nana?
I am using ubuntu 18.04 and I've read that I can do that with Makefile but I haven't understood how.. I want to use Premake to organize my project so that I can say to Premake that it needs to include the Nana library and then Premake "smartly" find all shared libraries..
When I used Premake and I linked the Nana library (statically) the compiler gaves me a lot of errors...
all the errors say:
undefined reference to: X...
So I need to include all the shared libraries that Nana needs, but how?
gcc has no idea about inter-library dependencies. You need a build system (which would use gcc as the compiler) for that.
Now, the Nana library uses the CMake build system. Thus a good solution to the problem should be to get the authors of Nana to properly export the library's CMake targets, and distribute a .cmake file which you can then import if you also build with CMake.
Alternatively - perhaps such a CMake file already exists somewhere (I haven't been able to quickly find it though).
I would ask about this in the Nana forums.
I'm trying to build libmcrypt library to use it with my project. It happened so, that they do not provide any kind of assistance.
First I've faced a problem with -no-undefined flag for gcc which is not further supported. I've replaced -no-undefined with -Wl,-no-undefined in makefiles and it does the trick.
But anyway I'am having problems. Lib is builded in .a files. I can see them in my C:\MinGW\msys\1.0\local\lib folder (it is analogue for /usr/local/lib folder in MinGW). But I need .dll library, not static .a .
So: what else must I change in makefiles to make MinGW build dll with header and debug info for it?
I've installed GCC 4.6.3 into a non-system path on a Mac system and it works fine. However, GCC wants to use code from libgcc for all the binaries I compile, and running otool -L shows that these compiled programs look for libgcc_s.1.dylib in GCC's install path. I can override this by passing -static-libgcc, which just compiles the stuff needed into the binary and that's fine. The problem is this only seems to work with executables, not shared libraries. If I use GCC to compile some third-party lib I want to use in one of my programs as a .dylib, these libraries still look for libgcc_s.1.dylib in the local GCC install path even if I specify -static-libgcc! Needless to say, this is a problem as there's no guarantee that those libraries will find libgcc when run on some other system.
I tried this with ffmpeg. If I look at config.log, the -static-libgcc is most certainly being used. GCC is just not linking libgcc statically with the resulting dylibs. I even tried the -nostdlib, -nostartfiles and -nodefaultlibs options but they were ignored. Again, I checked config.log and they're definitely there!
I believe this is to do with throwing exceptions across the shared library boundary. This page says:
There are several situations in which an application should use the
shared libgcc instead of the static version. The most common of these
is when the application wishes to throw and catch exceptions across
different shared libraries. In that case, each of the libraries as
well as the application itself should use the shared libgcc.
Therefore, the G++ and GCJ drivers automatically add -shared-libgcc
whenever you build a shared library or a main executable, because C++
and Java programs typically use exceptions, so this is the right thing
to do.
The rest of that sections gives a possible workaround (it appears) and that is to use the GCC driver to link your shared library, however if the statically-linked library throws exceptions you'll probably get a Segmentation Violation.
I am able to build the shared object successfully using the holy native compiler "xlc" on AIX.It does build the shared object library but does not install the shared object library.
Configure command is:
./configure --prefix=/PATH/to/install --exec-prefix=/PATH/to/install --enable-shared --enable-static=no --enable-module=so --build=powerpc-ibm-aix5.3.0.0 --host=powerpc-ibm-aix5.3.0.0 LDFLAGS="-G -shared"
Any help would be appreciated?
So you are trying to compile to the shared library location.
I would suggest seeing if you can compile/link to your local directory.
If that works, try copying the new library to the correct directory. It may be that the oldshared library is open by some process and therefore can't be overwritten.
Are you getting any error messages?
I could install the shared library successfully when i had to exclusively export LDFLAGS as "-brtl -L/path/to/install".
Under AIX, there are two types of shared libraries, AIX style, and SysV compat libs.
AIX style libs are archvies that can contain static libraries as well as multiple versions of shared libraries, and have names like libFOO.a
SysV-compat libs have names like libFoo.so and are more like what you would find on Linux.
Libtool will build either type. If you want SysV-compat libs, add -Wl,-brtl to LDFLAGS.
My guess is that you see /PATH/to/install/lib/libFOO.a and are assuming that it's a static library, when in fact, it's an AIX shared library.