I am having liavcodec.a static library and header files of this library.
libavcodec.a
I added this library and their header files into my project and there is no error. I can see this library added in Target->Info->General and i have edited the Header Search Path also.
I can add header file #import “avcodec.h” into xcode project also. I can use all the variables which have been declared in structure of that file. But i am trying to use any function from that class, i am getting some errors like,
Test.m
—-
“-avcodec_register_all”, referenced from:
-[Test initialize] in Test.o
Symbol(s) not found
collect2: id returned 1 exit status
—-
Do you what is the problem?
Many thanks.
Provide implementation of your [test initialize] method. Also provide the configuration command which you used to build the static library.
Try rebuilding the library, the method avcodec_register_all should be directly accessible through allcodecs.c file if the library is included in target and header search path is properly configured. Probably the library is corrupt, just as tedge says.
Just as a sanity check, verify that your library file contains the expected symbols; Type this in a terminal window (replacing path/to with the correct path):
nm -g /path/to/libavcodec.a | grep avcodec_register_all
(If the command's output is just a blank line, then the library file is probably corrupt).
Related
I am trying to compile a project using cmake. I need to use an external static library in src1.c so I utilized target_link_libraries to link it to the object file. However, I am getting some complains about missing functions in src1.c which should be in the external library.
add_library(input_output OBJECT
src/src1.c
src/src2.c
src/src3.c)
find_library(EXTERNAL_LIB NAMES libexternallib.a PATHS ~/lib)
target_link_libraries(input_output PRIVATE
"${EXTERNAL_LIB}")
So I am not sure what I should do at this point. the logic sounds right at least
UPDATE1: I also added the external library directly into the linker command
add_compile_options(-Wall -Wextra --std=c99 -L~/lib -lexternallib)
add_link_options(-L~/lib -lexternallib)
but this added the library flags before the object file for the linker command, which leads to some other problem with ordering the linker arguments
It's hard to say what is really the reason for your error here, but I'll give it a try.
First of all, you don't need to link manually with add_compile_options or add_link_options. The cmake command target_link_libraries is doing that for you.
What I could imagine, because of the missing functions, that you need to add a header include directory from the dependency.
e.g.:
target_include_directories(input_output PRIVATE /path/to/external_library_header)
I have simple question related to LIB command I have one sum.cpp file which contains one function add(int,int).
Now library name a.lib depends on sum.obj file and one another library name b.lib which depends upon a.lib and sum.obj
so scenario is
a.lib: sum.obj
b.lib : sum.obj a.lib
everything works fine but my doubt is why lib command not issuing duplicate warning or error.
Using CMake I'm able to cross-compile and create a static library which depends on other static libraries. However, the resulting static library doesn't include the "content" of the other static libraries. Therefore, I want to create an archive, i.e. a static library, that actually includes everything (all the object files).
To this aim, I've tried to use the following directive in CMakeLists.txt:
add_custom_target(combined ALL COMMAND ${CMAKE_AR} rc libcombined.a $<TARGET_FILE:target1> $<TARGET_FILE:target2> $<TARGET_FILE:target3>)
CMAKE_AR is set to an absolute path where my cross-compiler(archiver?) is; its values is something like: c:/arm/arm-none-eabi-ar.exe
However, when I try to build the project (make && make install), I receive the following error:
'..' is not recognized as an internal or external command, operable program or batch file.
make[2]: *** [src/CMakeFiles/combined] Error 1
If I open the build.make file where the src/CMakeFiles/combined is, I have something similar to this:
src/CMakeFiles/combined:
cd absolute-path-to-the-build-folder/src && ../../relative-path-to-the-archiver-executable/arm-none-eabi-ar.exe rc libcombined.a absolute-path-to-target1-archive absolute-path-to-target2-archive absolute-path-to-target3-archive
If I manually replace the relative path to the archiver executable with the absolute path, the new archive is created correctly. The same happens if I just add quotes in the specified archiver path.
At this point, I think it might be something related to Windows and/or to the make utility which doesn't interpret correctly the command/path.
Therefore, I have the following question:
Why is the CMAKE_AR value converted to a relative path from an absolute path?
How can I solve this without involving external scripts?
About last point, I tried to escape the CMAKE_AR path with quotes, but then I get the error: "COMMAND may not contain literal quotes".
What you want to do is create an object library that depends on your various static libraries in order to get a single library that contains all the dependencies.
I have a CMake setup to link together 4 static libraries and 1 shared one into a top level shared library (Let's call it Top.dll). This will work fine except for one thing. I have a module definition file that expresses which symbols should be public. Top.dll builds and so far so good.
Now when I try to link an executable with Top.dll via CMake I get linker errors for every public symbol claiming it is defined in two places (Top.dll and the static library in which it was actually defined) even though Top.dll contains no original definitions of its own. If I remove the static library then as expected I get unresolved symbol errors. If I remove the module definition file, I get the same. It seems like it is either there zero times or twice. Is there some setting I am missing here? I don't think I'm using CMake in a non-basic way...
UPDATE An explanation via CMake
# setup the lib
add_subdirectory(vendor/A) #shared library
add_subdirectory(vendor/B) #static library
add_subdirectory(vendor/C) #static library
add_library(Top SHARED ${ALL_SRC_FILES})
target_link_libraries(Top A B C)
set_target_properties(Top PROPERTIES LINK_FLAGS
"/def:${PROJECT_SOURCE_DIR}/definitions.def") #contains symbols from B
add_subdirectory(C/Tests)
# CMakeLists.txt from C/Tests
add_executable(Tests ${SRC_FILES})
target_link_libraries(Tests Top)
The above is simplified, but I will get errors like the following at the point that the C/tests project is compiled:
B.lib(xxx.obj) : error LNK2005: _ABC already defined in Top.lib(Top.dll)
If I remove B.lib from the target_link_libraries call, then as expected I get unresolved symbols. If I remove the /def line, same result.
I've been able to get around this by setting the target_link_libraries of B and C to private. This may or may not be the correct solution and I will wait for other answers. If I don't do this it appears that the dependency is carried up to the final executable (So it links to both Top.dll and B.lib, etc).
I'm trying to compile the MultiBoost Library with C++11 but I can't make it work. The problem seems to be with the BZip2 Library that is used internally. More specificly there is a wrapper called Bzip2Wrapper to provide a c++ interface to the C library. All the files of the C library are included in the same folder. When using the default make file everything works but when I change
project(multiboost)
to
project(multiboost CXX)
I get the following errors:
libMultiBoostLib.a(Serialization.cpp.o): In function `Bzip2WrapperReader::open(char const*)':
Serialization.cpp:(.text._ZN18Bzip2WrapperReader4openEPKc[_ZN18Bzip2WrapperReader4openEPKc]+0x97): undefined reference to `BZ2_bzReadOpen'
Serialization.cpp:(.text._ZN18Bzip2WrapperReader4openEPKc[_ZN18Bzip2WrapperReader4openEPKc]+0xc5): undefined reference to `BZ2_bzReadClose'
libMultiBoostLib.a(Serialization.cpp.o): In function `Bzip2WrapperReader::close()': ...
The CMakeList file looks like this
# Bzip2
file(GLOB bzip2_SRCS "${BASEPATH}/Bzip2/*.cpp" "${BASEPATH}/Bzip2/*.c" "${BASEPATH}/Bzip2/*.h")
add_library(Bzip2Lib STATIC ${bzip2_SRCS})
#add_library(bzip2 SHARED ${bzip2_lib_SRCS})
...
# adding library to the exec
target_link_libraries(multiboost MultiBoostLib Bzip2Lib)
Any ideas what could go wrong? I don't even know what the problem is.
Thanks!
This does not look like a C++11 error but an error in the Build system.
I have not looked at the Code, but from the output you added something like this
target_link_libraries(MultiBoostLib PUBLIC Bzip2Lib)
should add the missing dependency from libMultiBoostLib on libBzip2Lib.
I found the problem. I was adding "CXX" to my project description which disabled the use of C. Therefore the libraries (in C) could not be compiled. Changing it to "project(name C CXX)" solved this issue. I then also needed to include the line "set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")" to enable C++11 support. Now everything is working.
Thanks a lot!