Output of 'make' is a shared object and not an executable - c++

Question

Edit: It appears to be a g++ issue, as compiling with clang++ does output an executable file.
I've written a C++ application that has a main function, creates an application window, loads a 3D fbx file and draws that using opengl. To create the Makefile for compiling i'm using a CMakeLists.txt file:
cmake_minimum_required(VERSION 2.8)
project(solight)
set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")
INCLUDE_DIRECTORIES(lib/include)
###########################################
#SET THIS TO X32 IN CASE OF A 32 BIT SYSTEM
###########################################
set (ARCH x64)
set (SRC_LIST
src/assetmanager.cpp src/assetmanager.h
src/mesh.cpp src/mesh.h
src/model.cpp src/model.h
src/modelloader.h
src/main.cpp
src/math.h
src/fbxmodelloader.cpp src/fbxmodelloader.h
src/rendermodule.h
src/openglrendermodule.cpp src/openglrendermodule.h
src/textureloader.h
src/engine.cpp src/enginemodules.cpp src/engine.h
)
##########################
#EXTERNAL LIBRARY HANDLING
##########################
set (LINUX_DEPS
libfbxsdk.a
pthread
libSDL2.a
GL
libGLEW.a
dl
)
set (WIN32_DEPS
)
set (APPLE_DEPS
)
if (UNIX AND NOT APPLE)
set (DEPS ${LINUX_DEPS})
set (OS Linux)
endif()
if (APPLE)
set (DEPS ${APPLE_DEPS})
set (OS Apple)
endif()
if (WIN32)
set (DEPS ${WIN32_DEPS})
set (OS WIN32)
endif()
LINK_DIRECTORIES(${CMAKE_SOURCE_DIR}/lib/${OS}/${ARCH})
####################
#EXECUTBALE CREATION
####################
add_executable(${PROJECT_NAME} ${SRC_LIST})
target_link_libraries(${PROJECT_NAME} ${DEPS})
So after running the makefile that cmake created, the output is not an executable as expected, but a shared object file. If i run the file command on it this is the output:
solight: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=f20c07c8743a70bca20d4a0d9f50fcb108b8140e, not stripped
When executing
/lib64/ld-linux-x86-64.so.2 ./solight --verify
the program executes as it should.
But when i execute the file through the terminal it runs just fine, creates the window and renders the model.
Any explantion as to why this is a shared object file?
Thanks in advance.
Edit:
When running
make VERBOSE=1
the output is:
/usr/bin/cmake -H/home/wouter/Documents/Solight -B/home/wouter/Documents/Solight/build --check-build-system CMakeFiles/Makefile.cmake 0
/usr/bin/cmake -E cmake_progress_start /home/wouter/Documents/Solight/build/CMakeFiles /home/wouter/Documents/Solight/build/CMakeFiles/progress.marks
make -f CMakeFiles/Makefile2 all
make[1]: Entering directory '/home/wouter/Documents/Solight/build'
make -f CMakeFiles/solight.dir/build.make CMakeFiles/solight.dir/depend
make[2]: Entering directory '/home/wouter/Documents/Solight/build'
cd /home/wouter/Documents/Solight/build && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/wouter/Documents/Solight /home/wouter/Documents/Solight /home/wouter/Documents/Solight/build /home/wouter/Documents/Solight/build /home/wouter/Documents/Solight/build/CMakeFiles/solight.dir/DependInfo.cmake --color=
Dependee "/home/wouter/Documents/Solight/build/CMakeFiles/solight.dir/DependInfo.cmake" is newer than depender "/home/wouter/Documents/Solight/build/CMakeFiles/solight.dir/depend.internal".
Dependee "/home/wouter/Documents/Solight/build/CMakeFiles/CMakeDirectoryInformation.cmake" is newer than depender "/home/wouter/Documents/Solight/build/CMakeFiles/solight.dir/depend.internal".
Scanning dependencies of target solight
make[2]: Leaving directory '/home/wouter/Documents/Solight/build'
make -f CMakeFiles/solight.dir/build.make CMakeFiles/solight.dir/build
make[2]: Entering directory '/home/wouter/Documents/Solight/build'
[ 11%] Building CXX object CMakeFiles/solight.dir/src/assetmanager.cpp.o
/usr/bin/c++ -I/home/wouter/Documents/Solight/lib/include -std=c++14 -o CMakeFiles/solight.dir/src/assetmanager.cpp.o -c /home/wouter/Documents/Solight/src/assetmanager.cpp
[ 22%] Building CXX object CMakeFiles/solight.dir/src/mesh.cpp.o
/usr/bin/c++ -I/home/wouter/Documents/Solight/lib/include -std=c++14 -o CMakeFiles/solight.dir/src/mesh.cpp.o -c /home/wouter/Documents/Solight/src/mesh.cpp
[ 33%] Building CXX object CMakeFiles/solight.dir/src/model.cpp.o
/usr/bin/c++ -I/home/wouter/Documents/Solight/lib/include -std=c++14 -o CMakeFiles/solight.dir/src/model.cpp.o -c /home/wouter/Documents/Solight/src/model.cpp
[ 44%] Building CXX object CMakeFiles/solight.dir/src/main.cpp.o
/usr/bin/c++ -I/home/wouter/Documents/Solight/lib/include -std=c++14 -o CMakeFiles/solight.dir/src/main.cpp.o -c /home/wouter/Documents/Solight/src/main.cpp
[ 55%] Building CXX object CMakeFiles/solight.dir/src/fbxmodelloader.cpp.o
/usr/bin/c++ -I/home/wouter/Documents/Solight/lib/include -std=c++14 -o CMakeFiles/solight.dir/src/fbxmodelloader.cpp.o -c /home/wouter/Documents/Solight/src/fbxmodelloader.cpp
[ 66%] Building CXX object CMakeFiles/solight.dir/src/openglrendermodule.cpp.o
/usr/bin/c++ -I/home/wouter/Documents/Solight/lib/include -std=c++14 -o CMakeFiles/solight.dir/src/openglrendermodule.cpp.o -c /home/wouter/Documents/Solight/src/openglrendermodule.cpp
[ 77%] Building CXX object CMakeFiles/solight.dir/src/engine.cpp.o
/usr/bin/c++ -I/home/wouter/Documents/Solight/lib/include -std=c++14 -o CMakeFiles/solight.dir/src/engine.cpp.o -c /home/wouter/Documents/Solight/src/engine.cpp
[ 88%] Building CXX object CMakeFiles/solight.dir/src/enginemodules.cpp.o
/usr/bin/c++ -I/home/wouter/Documents/Solight/lib/include -std=c++14 -o CMakeFiles/solight.dir/src/enginemodules.cpp.o -c /home/wouter/Documents/Solight/src/enginemodules.cpp
[100%] Linking CXX executable solight
/usr/bin/cmake -E cmake_link_script CMakeFiles/solight.dir/link.txt --verbose=1
/usr/bin/c++ -std=c++14 CMakeFiles/solight.dir/src/assetmanager.cpp.o CMakeFiles/solight.dir/src/mesh.cpp.o CMakeFiles/solight.dir/src/model.cpp.o CMakeFiles/solight.dir/src/main.cpp.o CMakeFiles/solight.dir/src/fbxmodelloader.cpp.o CMakeFiles/solight.dir/src/openglrendermodule.cpp.o CMakeFiles/solight.dir/src/engine.cpp.o CMakeFiles/solight.dir/src/enginemodules.cpp.o -o solight -L/home/wouter/Documents/Solight/lib/Linux/x64 -rdynamic -Wl,-Bstatic -lfbxsdk -Wl,-Bdynamic -lpthread -Wl,-Bstatic -lSDL2 -Wl,-Bdynamic -lGL -Wl,-Bstatic -lGLEW -Wl,-Bdynamic -ldl -Wl,-rpath,/home/wouter/Documents/Solight/lib/Linux/x64
/home/wouter/Documents/Solight/lib/Linux/x64/libfbxsdk.a(fbxutils.o): In function `fbxsdk_2015_1::FbxPathUtils::GenerateFileName(char const*, char const*)':
(.text+0x4c8): warning: the use of `tempnam' is dangerous, better use `mkstemp'
make[2]: Leaving directory '/home/wouter/Documents/Solight/build'
[100%] Built target solight
make[1]: Leaving directory '/home/wouter/Documents/Solight/build'
/usr/bin/cmake -E cmake_progress_start /home/wouter/Documents/Solight/build/CMakeFiles 0

Answer 1

This may happen when application is compiled with special CFLAGS e.g. -pie -fPIE:
$ echo 'int main() { return 0; }' | gcc -x c - -fPIE -pie
$ file a.out
a.out: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.24,
Perhaps you could run your make with VERBOSE=1 and see if that's the case? In general file may use heuristics to identify filetype so you shouldn't rely on it too heavily.
As for your error with ld.so, you are using the wrong, 32-bit, dynamic linker to run 64-bit app. Use /lib64/ld-linux-x86-64.so.2 instead (as file told you).
EDIT: Another option is that your GCC is built with --enable-default-pie which seems to be the case for modern Ubuntu. You can disable this feature by cmaking with CFLAGS=-no-pie (or -nopie, depending on GCC version) but I'd rather not do that - PIE'ed executables make your system safer by allowing ASLR to do better job.

Answer 2

I found the root cause is the -shared flag in CMAKE_EXE_LINKER_FLAGS.
when I delete -shared, everything is ok.