I'm struggling to link my program on Linux. I've given up and hacked the Makefile I'm using to use an archive group. However, I've still got a bunch of undefined references to things I know I export- the build succeeds on Windows and if I build LLVM from source.
The full command is
g++ -o ../Build/x64/Release/SemanticTest -s -m64 -L/usr/lib64 -L/usr/lib/llvm-3.6/lib -L/opt/wide/boost_1_59_0/stage/lib -L../Build/x64/Release -Wl,--start-group ../Obj/SemanticTest/x64/Release/test.o ../Obj/SemanticTest/x64/Release/main.o -lUtil -lSemantic -lParser -lLexer -lm -lstdc++ -lclangFrontend -lclangSerialization -lclangDriver -lclangTooling -lclangCodeGen -lclangParse -lclangSema -lclangAnalysis -lclangRewriteFrontend -lclangRewrite -lclangEdit -lclangAST -lclangLex -lclangBasic -lLLVMLTO -lLLVMObjCARCOpts -lLLVMLinker -lLLVMBitWriter -lLLVMIRReader -lLLVMAsmParser -lLLVMR600CodeGen -lLLVMipo -lLLVMVectorize -lLLVMR600AsmParser -lLLVMR600Desc -lLLVMR600Info -lLLVMR600AsmPrinter -lLLVMSystemZDisassembler -lLLVMSystemZCodeGen -lLLVMSystemZAsmParser -lLLVMSystemZDesc -lLLVMSystemZInfo -lLLVMSystemZAsmPrinter -lLLVMHexagonDisassembler -lLLVMHexagonCodeGen -lLLVMHexagonDesc -lLLVMHexagonInfo -lLLVMNVPTXCodeGen -lLLVMNVPTXDesc -lLLVMNVPTXInfo -lLLVMNVPTXAsmPrinter -lLLVMCppBackendCodeGen -lLLVMCppBackendInfo -lLLVMMSP430CodeGen -lLLVMMSP430Desc -lLLVMMSP430Info -lLLVMMSP430AsmPrinter -lLLVMXCoreDisassembler -lLLVMXCoreCodeGen -lLLVMXCoreDesc -lLLVMXCoreInfo -lLLVMXCoreAsmPrinter -lLLVMMipsDisassembler -lLLVMMipsCodeGen -lLLVMMipsAsmParser -lLLVMMipsDesc -lLLVMMipsInfo -lLLVMMipsAsmPrinter -lLLVMAArch64Disassembler -lLLVMAArch64CodeGen -lLLVMAArch64AsmParser -lLLVMAArch64Desc -lLLVMAArch64Info -lLLVMAArch64AsmPrinter -lLLVMAArch64Utils -lLLVMARMDisassembler -lLLVMARMCodeGen -lLLVMARMAsmParser -lLLVMARMDesc -lLLVMARMInfo -lLLVMARMAsmPrinter -lLLVMPowerPCDisassembler -lLLVMPowerPCCodeGen -lLLVMPowerPCAsmParser -lLLVMPowerPCDesc -lLLVMPowerPCInfo -lLLVMPowerPCAsmPrinter -lLLVMSparcDisassembler -lLLVMSparcCodeGen -lLLVMSparcAsmParser -lLLVMSparcDesc -lLLVMSparcInfo -lLLVMSparcAsmPrinter -lLLVMTableGen -lLLVMDebugInfo -lLLVMOption -lLLVMX86Disassembler -lLLVMX86AsmParser -lLLVMX86CodeGen -lLLVMSelectionDAG -lLLVMAsmPrinter -lLLVMX86Desc -lLLVMMCDisassembler -lLLVMX86Info -lLLVMX86AsmPrinter -lLLVMX86Utils -lLLVMMCJIT -lLLVMLineEditor -lLLVMInstrumentation -lLLVMInterpreter -lLLVMExecutionEngine -lLLVMRuntimeDyld -lLLVMCodeGen -lLLVMScalarOpts -lLLVMProfileData -lLLVMObject -lLLVMMCParser -lLLVMBitReader -lLLVMInstCombine -lLLVMTransformUtils -lLLVMipa -lLLVMAnalysis -lLLVMTarget -lLLVMMC -lLLVMCore -lLLVMSupport -ldl -lpthread -lncurses -lboost_program_options -larchive -lz -Wl,--end-group
How can I convince ld to actually find the stuff I export?
This has something to do with incompatible ABIs. I had old cached binaries lying around that I needed to clear out. I rebuilt my own work with Clang 3.6 and now I can mostly link. There's just functions that use std::string left between my code and my used libraries, namely LLVM&Clang and Boost.
Ultimately, I think this is probably due to all the stuff I did to try to work with both Precise and Willy with the same build scripts, like install Clang 3.6 and try to use that as the compiler. A clean install of Willy doing the obvious thing works just fine.
Related
I am very much lost here and could really use some help.
I'm working on an Honours project for next year that involves a physics simulation using Bullet and Vulkan for rendering. After a few months of work I have most of the project functioning. It needs a lot of refactoring and cleaning which will be the next stage.
I have been using a makefile but wish to migrate to CMake for a few reasons. Mainly because it seems to be the standard and because I want to compile for different OS's in the future (I'm running Linux but may need to deploy on Windows or Mac). Finally, I was recompiling the whole project for even a small change, which was beginning to become a problem as I started Unit Testing more.
The old makefile is as follows :
ROOT_DIR:=$(shell dirname $(realpath $(firstword $(MAKEFILE_LIST))))
OWN_INCLUDES = \
-I$(ROOT_DIR)/src/Domain \
-I$(ROOT_DIR)/src/Vk \
-I$(ROOT_DIR)/src/Ui \
-I$(ROOT_DIR)/src/Service
ADD_INCLUDES = \
-I/opt/bullet3-master/src \
-I/opt/vk_mem_alloc \
-I/opt/stb_image \
-I/opt/tiny_obj_loader/ \
-I/opt/imgui-vulkan/
BULLET_INCLUDE_PATHS_LIBS = -L/opt/bullet3-master/src/BulletCollision/ \
-L/opt/bullet3-master/src/BulletDynamics/ \
-L/opt/bullet3-master/src/LinearMath/ \
-lBulletDynamics -lBulletCollision -lLinearMath
VULKAN_SDK_PATH = /opt/Vulkan_SDK/1.2.162.1/x86_64
CFLAGS = -std=c++17 -I$(VULKAN_SDK_PATH)/include $(OWN_INCLUDES) $(ADD_INCLUDES)
LDFLAGS = -L$(VULKAN_SDK_PATH)/lib `pkg-config --static --libs glfw3` -lvulkan $(BULLET_INCLUDE_PATHS_LIBS)
IMGUI_CPP_PATHS = /opt/imgui-vulkan/*.cpp
OWN_CPP_PATHS = src/*.cpp src/Domain/*.cpp src/Vk/*.cpp src/Ui/*.cpp src/Service/*.cpp
###### Unit Testing Paths
UNIT_TEST_INCLUDE = -I/opt/catch-header/
UNIT_TESTS_PATH = $(ROOT_DIR)/unit_tests/*.cpp
VulkanRun: $(OWN_CPP_PATHS) $(IMGUI_CPP_PATHS)
g++ $(CFLAGS) -o VulkanRun $(OWN_CPP_PATHS) $(IMGUI_CPP_PATHS) $(LDFLAGS)
Unit_Test: $(UNIT_TESTS_PATH) src/Domain/*.cpp src/Vk/*.cpp src/Ui/*.cpp src/Service/*.cpp $(IMGUI_CPP_PATHS)
g++ $(UNIT_TEST_INCLUDE) $(CFLAGS) -o Unit_Test $(UNIT_TESTS_PATH) src/Domain/*.cpp src/Vk/*.cpp src/Ui/*.cpp src/Service/*.cpp $(IMGUI_CPP_PATHS) $(LDFLAGS)
VulkanDebug: $(OWN_CPP_PATHS) $(IMGUI_CPP_PATHS)
g++ $(CFLAGS) -g -o VulkanDebug $(OWN_CPP_PATHS) $(IMGUI_CPP_PATHS) $(LDFLAGS)
VulkanOpt: $(OWN_CPP_PATHS) $(IMGUI_CPP_PATHS)
g++ $(CFLAGS) -O3 -o VulkanOpt $(OWN_CPP_PATHS) $(IMGUI_CPP_PATHS) $(LDFLAGS)
.PHONY: test clean
run: VulkanRun
LD_LIBRARY_PATH=$(VULKAN_SDK_PATH)/lib
VK_LAYER_PATH=$(VULKAN_SDK_PATH)/etc/vulkan/explicit_layer.d
./VulkanRun
test: Unit_Test
LD_LIBRARY_PATH=$(VULKAN_SDK_PATH)/lib
VK_LAYER_PATH=$(VULKAN_SDK_PATH)/etc/vulkan/explicit_layer.d
./Unit_Test
debug: VulkanDebug
LD_LIBRARY_PATH=$(VULKAN_SDK_PATH)/lib
VK_LAYER_PATH=$(VULKAN_SDK_PATH)/etc/vulkan/explicit_layer.d
optimise: VulkanOpt
LD_LIBRARY_PATH=$(VULKAN_SDK_PATH)/lib
VK_LAYER_PATH=$(VULKAN_SDK_PATH)/etc/vulkan/explicit_layer.d
./VulkanOpt
7 clean:
rm -f VulkanRun
rm -f Unit_Test
rm -f VulkanDebug
rm -f VulkanOpt
I installed cmake using the latest install script for 3.21.0.
I created a CMakeLists.txt in the root of the project as follows :
cmake_minimum_required(VERSION 3.21.0)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17")
project(LanderSim)
file(GLOB_RECURSE SOURCES "src/**.cpp")
add_executable(main ${SOURCES})
find_package(Bullet CONFIG REQUIRED)
if (BULLET_FOUND)
include_directories(${BULLET_INCLUDE_DIRS})
target_link_libraries(main PRIVATE LinearMath Bullet3Common BulletDynamics BulletSoftBody)
endif (BULLET_FOUND)
After many hours of trying I decided to try vcpkg. Following the install instructions from bullet :
git clone https://github.com/Microsoft/vcpkg.git
cd vcpkg
./bootstrap-vcpkg.sh
./vcpkg integrate install
./vcpkg install bullet3
This resulted in errors of
CMake Error at CMakeLists.txt:11 (find_package):
Could not find a package configuration file provided by "Bullet" with any
of the following names: BulletConfig.cmake bullet-config.cmake
Looking in CMakeCache.txt i see "Bullet_DIR:PATH=Bullet_DIR-NOTFOUND"
I found the BulletConfig.make file in "/home/ash/vcpkg/installed/x64-linux/share/bullet3" and in "/home/ash/vcpkg/packages/bullet3_x64-linux/share/bullet3" and set the MakeCache.txt var Bullet_DIR:PATH to these variables (tested one at a time).
Running again I get CMake set_and_check() function not recognised. Or something to that effect. Looking in the BulletConfig.make file I see these set_and_check() functions aren't recognised by the linter. I cant find any information about them being deprecated online but I assume this is the case. So I change to set() and CMake then succeeds and builds its files.
Running make I then get an error.
fatal error: btBulletDynamicsCommon.h: No such file or directory,
#include <btBulletDynamicsCommon.h>
I tried prepending bullet/ to the include path as others had this issue but it causes the same error.
So I must be doing something wrong and I'm obviously not understanding the process that CMake uses to add includes and link libraries. I'm sure, given the popularity of CMake, that there must be something obvious. But I've spent about 10 hours over a few days searching and trying different variations and I'm starting to get very frustrated.
I've bounced off CMake before (hence why I was working with a makefile for months), but I'm determined to do this properly. I just could really use some help if anyone knows how to get CMake to generate a makefile that can see a package installed with vcpkg.
Or indeed if the vcpkg of Bullet is out of date, then a way to link and include it with CMake alone would be great. I just thought vcpkg would be easier as it provides a cleaner file structure by default as well as a CMake config file.
Thanks.
EDIT1
I've used 'cmake .' and 'cmake . -DCMAKE_TOOLCHAIN_FILE=/home/ash/vcpkg/scripts/buildsystems/vcpkg.cmake' to build the makefile. Both result in the same missing headers errors when calling make.
EDIT2
All CMake files were removed from the project (except CMakeLists.txt) before each call to cmake to ensure no values were stored there.
EDIT3
Poked around a bit more. Here is the BulletConfig.cmake file :
#
# BulletConfig.cmake(.in)
#
# Use the following variables to compile and link against Bullet:
# BULLET_FOUND - True if Bullet was found on your system
# BULLET_USE_FILE - The file making Bullet usable
# BULLET_DEFINITIONS - Definitions needed to build with Bullet
# BULLET_INCLUDE_DIR - Directory where Bullet-C-Api.h can be found
# BULLET_INCLUDE_DIRS - List of directories of Bullet and it's dependencies
# BULLET_LIBRARIES - List of libraries to link against Bullet library
# BULLET_LIBRARY_DIRS - List of directories containing Bullet' libraries
# BULLET_ROOT_DIR - The base directory of Bullet
# BULLET_VERSION_STRING - A human-readable string containing the version
set(PACKAGE_PREFIX_DIR /home/ash/installed/x64-linux)
set ( BULLET_FOUND 1 )
set ( BULLET_USE_FILE "${PACKAGE_PREFIX_DIR}/share/bullet3/UseBullet.cmake" )
set ( BULLET_DEFINITIONS "" )
set ( BULLET_INCLUDE_DIR "${PACKAGE_PREFIX_DIR}/include/bullet" )
set ( BULLET_INCLUDE_DIRS "${PACKAGE_PREFIX_DIR}/include/bullet" )
set ( BULLET_LIBRARIES "LinearMath;Bullet3Common;BulletInverseDynamics;BulletCollision;BulletDynamics;BulletSoftBody" )
set ( BULLET_LIBRARY_DIRS "${PACKAGE_PREFIX_DIR}/lib" )
set ( BULLET_ROOT_DIR "${PACKAGE_PREFIX_DIR}" )
set ( BULLET_VERSION_STRING "3.17" )
# Load targets
if(NOT TARGET Bullet3Common)
file(GLOB CONFIG_FILES "${PACKAGE_PREFIX_DIR}/share/bullet3/*Targets.cmake")
foreach(f ${CONFIG_FILES})
include(${f})
endforeach()
set(_DIR)
endif()
As stated before a few of the set functions were set_and_check(). So I changed to set() as apparently cmake 3.21 has no set_and_check() function. After a little testing by printing message(), i found that PACKAGE_PREFIX_DIR was not being set anywhere. So that is why I've set it explicitly in this file. The variables are now set correctly as reported by message() in the CMakeLists.txt file. But still it make cannot find the header files.
EDIT4
I created an empty project and ran through each library I wanted to include. Everything works except for Bullet3. However it does now see the header files. What changed between the two CMakeFiles? Nothing as far as I can tell. I'll need to find out because I have to port this project over but in the meantime this is another issue with the package.
from /home/ash/projects/C++/CMakeImportTests/src/main.cpp:22:
/home/ash/vcpkg/installed/x64-linux/include/bullet/BulletCollision/CollisionDispatch/btCollisionWorld.h:77:10:
fatal error: LinearMath/btVector3.h: No such file or directory
77 | #include "LinearMath/btVector3.h"
I think this is the same issue as described #7877
If i remove all includes of Bullet but leave the CMakeList.txt untouched, we get this error:
[ 50%] Building CXX object CMakeFiles/main.dir/src/main.cpp.o
[100%] Linking CXX executable main
/usr/bin/ld: cannot find -lLinearMath
/usr/bin/ld: cannot find -lBullet3Common
/usr/bin/ld: cannot find -lBulletDynamics
/usr/bin/ld: cannot find -lBulletSoftBody
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/main.dir/build.make:104: main] Error 1
make[1]: *** [CMakeFiles/Makefile2:83: CMakeFiles/main.dir/all] Error 2
make: *** [Makefile:91: all] Error 2
Is this a clue that some environment variable is not set?
EDIT5
There seems to be an ordering dependency for the target_link_library call. The suggested usage is:
target_link_libraries(main PRIVATE LinearMath Bullet3Common BulletDynamics BulletSoftBody)
Checking bullet.pc in the libs/ directory i found
Libs: -L${libdir} -lBulletSoftBody -lBulletDynamics -lBulletCollision -lLinearMath
So I tried rearranging and following the pattern:
target_link_libraries(main PRIVATE BulletSoftBody BulletDynamics BulletCollision Bullet3Common LinearMath)
Additionally there was also a need to manually link directories.
target_link_directories(main PRIVATE ${BULLET_LIBRARY_DIRS})
This now compiles without error in my test project. It seems LinearMath must be after most of the other libraries (although it can be before Bullet3Common it seems).
For some reason it's still not finding the header files when I copy the exact same CMake commands over to my main project. So I'm not free of this yet.
I should say that I was able to remove the change I made to BulletConfig.cmake of setting PACKAGE_PREFIX_DIR statically.
So just to recap my issue. A small test project works and I can use bullet and number of other libraries that I use in my main project. But if i copy this working CMakeLists.txt to my main project it can no longer find the headers and throws this error :
btBulletDynamicsCommon.h: No such file or directory
8 | #include <btBulletDynamicsCommon.h>
Bullet_DIR:PATH=/home/ash/vcpkg/installed/x64-linux/share/bullet3 is the same in both cases.
After all that.
The set_and_include() error is a known issue and mathisloge over at vcpkg git said the Bullet package needs to be updated. The workaround is to change the calls to set().
The ordering of the target libraries is important. The suggested way in the Bullet vcpkg package is :
target_link_libraries(main PRIVATE LinearMath Bullet3Common BulletDynamics BulletSoftBody)
But this fails to compile. It should be:
target_link_libraries(main PRIVATE BulletSoftBody BulletDynamics BulletCollision Bullet3Common LinearMath)
Also had to tell cmake the link directories using :
target_link_directories(main PRIVATE ${BULLET_LIBRARY_DIRS})
Then I still had header missing errors. But after a restart things just started working again. Hopefully there is enough here to help someone if they hit similar problems.
As an alternative to accelerate, I'm trying to call CUDA code over Haskell's FFI.
Here's a simple program that fails to compile:
cuda_code.cu:
void cuda_init() {
cudaFree (0);
cudaThreadSynchronize ();
}
Test.hs:
foreign import ccall unsafe "cuda_init" cuda_init :: IO ()
main = cuda_init
I compiled with
$> nvcc -c -o cuda_code.o cuda_code.cu
$> ghc Test cuda_code.o
and got several linking errors (undefined reference to cudaFree, etc). This isn't terribly surprising, and the obvious solution (to me) is to link with NVCC using -pgml nvcc. (This worked when I was using Intel CILK+ in my C code: I simply changed the linker to ICC, and everything worked just fine.)
Howver, using NVCC to link results in the linking error:
ghc Test -pgml nvcc cuda_code.o
[1 of 1] Compiling Main ( Test.hs, Test.o )
Linking Test ...
nvcc fatal : Unknown option 'u'
Running
strace -v -f -e execve ghc Test -pgml nvcc cuda_code.o
(is there an easier way?) I discovered ghc is calling nvcc with
nvcc ... -L~/ghc... -L... -l... -l... -u ghczmprim_GHC... -u ghc...
I assume the -u options are intended for linking gcc (and apparently icc) with undefined symbols, something nvcc clearly doesn't like.
I have no knowledge about how GHC links files. Thoughts on how I can get GHC to link to my CUDA code?
--------EDIT-----------------
Someone suggested that I try linking with GCC (as usual), but pass in the necessary linker options to gcc so that it can link to the CUDA libraries. If anyone knows what these might be, this would probably work!
GHC uses /usr/lib/ghc/settings to determine compiler and linker options, and per-package files like /var/lib/ghc/package.conf.d/builtin_rts.conf to determine package-specific linker options. (Custom directory installation will have them in ${GHC}/lib/ghc-${VERSION}/settings and ${GHC}/lib/ghc-${VERSION}/package.conf.d respectively.)
Here is what I found for the RTS:
ld-options: -u ghczmprim_GHCziTypes_Izh_static_info -u
ghczmprim_GHCziTypes_Czh_static_info -u
ghczmprim_GHCziTypes_Fzh_static_info -u
ghczmprim_GHCziTypes_Dzh_static_info
...
According to the ld man page, the -u option defines a symbol as an undefined extern that must be defined somewhere else.
As far as I know this is the ONLY package that has these custom -u options in the ld-options: section of package.conf.d.
These must be unfortunately translated for a compiler/linker that uses a different option interface.
Be so kind and keep people posted about it on haskell-cafe#haskell.org. I'm sure there are others trying something like this too!
I figured out how to make this work.
cudaTest.cu:
// the `extern "C"` is important! It tells nvcc to not
// mangle the name, since nvcc assumes C++ code by default
extern "C"
void cudafunc() {
cudaFree(0);
cudaThreadSynchronize();
}
Test.hs
foreign import ccall unsafe "cudafunc" cudaFunc :: IO ()
main = cudaFunc
Compile with:
>nvcc -c -o cudaTest.o cudaTest.cu
>ghc --make Test.hs -o Test cudaTest.o -optl-lcudart
I also tried giving GHC the option -pgmc g++ and removing the extern "C" (which I expected to work), but got compile errors in some CUDA header files. There's probably some easy way to fix this so that you don't need to explicitly tag every function with extern "C".
I'm trying to write a simple program that uses EGL, but when I include bcm_host.h, gcc says it doesn't exist, so I add /opt/vc/include to the makefile, it says that another header is missing, I add another directory, and now, after 6 folders, I don't really want to do it anymore but gcc wants more. I have looked at the /opt/vc/src/hello_pi/Makefile.include file, and it adds just 3 folders. So the question is: what am I doing wrong?
Here's the makefile:
LIB_DIR = -L/opt/vc/lib
INCLUDE_DIRS = -I/opt/vc/include -I/opt/vc/include/interface/vcos/ -I/opt/vc/include/interface/vcos/pthreads -I/opt/vc/include/interface/vmc_host/linux -I/opt/vc/include/interface/vmcs_host -I/opt/vc/include/interface/vchi -I/usr/include/SDL -I-
LIBS = -lSDL
bin:
gcc $(LIB_DIRS) $(INCLUDE_DIRS) $(LIBS) main.c
I included bcm_host.h in a project where I was using code from the dispmax example. I have very similar makefile settings, with the exception that I added -lbcm_host as a library:
# Include the Broadcom hardware interface library
XINCDIR += /opt/vc/include
XINCDIR += /opt/vc/include/interface/vcos/pthreads
XLIBS += -L/opt/vc/lib/ -lbcm_host
That worked for me, although I wasn't trying to use EGL specifically. You probably need -lEGL instead or in addition.
Been dealing in linker hell for the past day and figured I'd throw this out there and see if anyone could help me out.
I have two shared libraries that I'm building: one called "libhttp" that has some helper functions for the http protocol which seems to be building for better or worse OK. The second is called "libvpcutil" which is causing the issues. It depends on symbols that are in libhttp so I link it against libhttp. Here's the compilation directive (exploded from the make file) with minor things like my personal path to openssl generified:
g++ -shared -Wl,-soname,libvpcutil.so.1 -o libvpcutil.so.1.0 vpcreg/registry.o \
vpcreg/vpcreg2.o dbase/dbase.o dbase/sqlutils.o diaglog/diaglog.o errmsg/errmsg.o \
faillib/faillib.o failover/failover.o initerr/init_err.o kmq/kmq.o kmq/publish.o \
kthread/kcom.o kthread/kthread.o libobdi/odi_serv.o mutex/mutex.o netserv/netserv.o \
newmem/newmem.o rmtstore/avlmem.o rmtstore/rmtstore.o rmtstore/shm_aloc.o \
servhand/servhand.o timers/timers.o vpcstamp/vpcstamp.o websql/websql.o types/blob.o \
types/hitime.o types/ticks.o types/timestamp.o odasm/odasm.o webvibapi/webvibapi.o \
vibusfeed/vibusfeed.o propstore/propstore2.o cardlib/cardlib.o cardlib/sortlist.o \
gapi/genapi.o -L/usr/lib/i386-linux-gnu -lm -lrt -lxml2 -lodbc -L/usr/lib/i386-linux-gnu -\
lcurl -Wl,-Bsymbolic-functions -Wl,-z,relro \
-L/pathtoopenssl/openssl -lssl -lcrypto -lxml2 -lreadline -\
lcurses -Wl,-rpath=.:/pathtobin/bin http/libhttp.so.1.0 ../ddldata/ddldata.o
../cardddl/cardddl.o ../gendata/generic.o
The compilation and linking completes successfully. Hopefully you noted the link step to http/libhttp.so.1.0.
Now, if I do a nm on libhttp.so.1.0, I get the following output (amongst others):
00015d5a T _ZN12http_cookiesC1Ev
00015d5a T _ZN12http_cookiesC2Ev
00015d7e T _ZN12http_cookiesD1Ev
00015d7e T _ZN12http_cookiesD2Ev
00011574 T _ZN12http_headers11url_expressERSo
00011466 T _ZN12http_headers12http_expressERSo
But when I do a nm on libvpcutil.so.1.0 I get essentially:
U _ZN12http_cookiesC1Ev
U _ZN12http_cookiesD1Ev
U _ZN12http_headers11url_expressERSo
U _ZN12http_headers3setEPKcRKSs
U _ZN12http_headers3setEPKcS1_
U _ZN12http_headersC1Ev
U _ZN12http_headersD1Ev
I'm obviously snipping here, but where I'm stuck here is the symbols are clearly defined in libhttp, I link against it for libvpcutil, but then the symbols are undefined in libvpcutil. This creates runtime errors.
Anyone see the issue?
That looks like the expected behaviour.
Linking to a shared library is not like linking to a static library, the required symbols do not get copied into the output file, you just get a reference to the symbol which must still be resolved at run-time. So it's normal that the symbols are shown as U by nm.
What are the run-time errors? It probably means the libhttp.so.1.0 library isn't found at run-time. You should be able to run ldd on libvpcutil.so and on the executable to see if they depend on libhttp.so.1.0 and if they're finding the right one.
Does libhttp.so.1.0 have a soname set? If it's not the same as the filename, do you have a symlink with the same name as the soname? (e.g. if the soname is libhttp.so.1 you'll need a symlink libhttp.so.1 -> libhttp.so.1.0). I also see your libhttp.so.1.0 is in a directory called http but that's not in your RPATH, so won't be found at runtime.
I am porting an application from Solaris to Linux
The object files which are linked do not have a main() defined. But compilation and linking is done properly in Solaris and executable is generated. In Linux I get this error
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../lib64/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
My problem is, I cannot include new .c/.o files since its a huge application and has been running for years. How can I get rid of this error?
Code extractes of makefile:
RPCAPPN = api
LINK = cc
$(RPCAPPN)_server: $(RPCAPIOBJ)
$(LINK) -g $(RPCAPIOBJ) -o $(RPCAPPN)_server $(IDALIBS) $(LIBS) $(ORALIBS) $(COMMONLIB) $(LIBAPI) $(CCLIB) $(THREADLIB) $(DBSERVERLIB) $(ENCLIB)
Try adding -nostartfiles to your linker options, i.e.
$(LINK) -nostartfiles -g ...
From the gcc documentation:
-nostartfiles
Do not use the standard system startup files when linking. The standard system libraries are used normally, unless -nostdlib or -nodefaultlibs is used.
This causes crt1.o not to be linked (it's normally linked by default) - normally only used when you implement your own _start code.
-shared link option must be used when you compile a .so
The issue for me was, I by mistake put int main() in a namespace. Make sure don't do that otherwise you will get this annoying link error.
Hope this helps anyone :)
I had similar result when trying to build a new test project with boost, and it turned out that I was missing one declaration :
#define BOOST_TEST_MODULE <yourtestName>
I had this same problem when creating my c project, and I forgot to save my main.c file, so there was no main function.
I had a similar result when compiling a Fortran program that had C++ components linked in. In my case, CMake failed to detect that Fortran should be used for the final linking. The messages returned by make then ended with
[100%] Linking CXX executable myprogram
/lib/../lib64/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
make[3]: *** [myprogram] Error 1
make[2]: *** [CMakeFiles/myprogram.dir/all] Error 2
make[1]: *** [CMakeFiles/myprogram.dir/rule] Error 2
make: *** [myprogram] Error 2
The solution was to add
set_target_properties(myprogram PROPERTIES LINKER_LANGUAGE Fortran)
to the CMakeLists.txt, so that make prints out:
[100%] Linking Fortran executable myprogram
[100%] Built target myprogram
I had the same issue with a large CMake project, after I moved some functions from one code file to another. I deleted the build folder, recreated it and rebuilt. Then it worked.
Generally, with suddenly appearing linker errors, try completely deleting your build folder and rebuilding first. That can save you the headaches from trying to hunt down an error that actually simply shouldn't be there: There might be CMake cache variables floating around that have the wrong values, or something was renamed and not deleted, ...
I had the same issue as to OP but on on FreeBSD 13.1.
What solved the issue was simply adding:
int main()
{
}
Since the .cpp file was only an object file containing definitions and declarations using:
extern "C"
{
<all definitions and declarations code goes here>
}
Every time I tried compiling this, the compiler kept throwing the same error as to OP.
So all I did was add an empty main() function all the way at the bottom and code compiled with no errors.