c++11 compile error in Mac OS X

[firatyenidunya]

I have been developing a C++ OpenGL game project. CMake is used as the build system. I'm using nanogui in the project as the external GUI library.

I was using glfw and glad outside of the nanogui and I managed to link them externally to the nanogui's CMake.

• I can successfully build the project on Linux.
• I could successfully build the library by itself from an another directory with the glfw and glad in it.
• But when I'm trying to build the same project on macOS Sierra, I get the following Make errors.

---

Everything successfully built and until up here

In file included from /Users/firat/Desktop/dungeon-defense/main.cpp:11:
In file included from /Users/firat/Desktop/dungeon-defense/include/GUI.h:5:
In file included from /Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/nanogui.h:14:
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:124:6: warning: scoped enumerations are a C++11 extension [-Wc++11-extensions]
enum class Cursor {
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:136:18: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
using Vector2f = Eigen::Vector2f;
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:138:18: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
using Vector3f = Eigen::Vector3f;
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:140:18: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
using Vector4f = Eigen::Vector4f;
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:142:18: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
using Vector2i = Eigen::Vector2i;
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:144:18: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
using Vector3i = Eigen::Vector3i;
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:146:18: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
using Vector4i = Eigen::Vector4i;
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:148:18: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
using Matrix3f = Eigen::Matrix3f;
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:150:18: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
using Matrix4f = Eigen::Matrix4f;
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:152:18: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
using VectorXf = Eigen::VectorXf;
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:154:18: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
using MatrixXf = Eigen::MatrixXf;
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:160:18: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
using MatrixXu = Eigen::Matrix<uint32_t, Eigen::Dynamic, Eigen::Dynamic>;
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:195:15: error: delegating constructors are permitted only in C++11
Color() : Color(0, 0, 0, 0) {}
^~~~~
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:216:11: error: delegating constructors are permitted only in C++11
: Color(color(0), color(1), color(2), alpha) { }
^~~~~
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:231:11: error: delegating constructors are permitted only in C++11
: Color(color.cast() / 255.f, alpha / 255.f) { }
^~~~~
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:240:43: error: delegating constructors are permitted only in C++11
Color(const Eigen::Vector3f &color) : Color(color, 1.0f) {}
^~~~~
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:250:11: error: delegating constructors are permitted only in C++11
: Color((Vector3f)(color.cast() / 255.f)) { }
^~~~~
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:260:11: error: delegating constructors are permitted only in C++11
: Color((Vector4f)(color.cast() / 255.f)) { }
^~~~~
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:272:11: error: delegating constructors are permitted only in C++11
: Color(Vector3f::Constant(intensity), alpha) { }
^~~~~
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:285:11: error: delegating constructors are permitted only in C++11
: Color(Vector3i::Constant(intensity), alpha) { }
^~~~~
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:302:49: error: delegating constructors are permitted only in C++11
Color(float r, float g, float b, float a) : Color(Vector4f(r, g, b, a)) { }
^~~~~
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:320:41: error: delegating constructors are permitted only in C++11
Color(int r, int g, int b, int a) : Color(Vector4i(r, g, b, a)) { }
^~~~~
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:475:65: error: a space is required between consecutive right angle brackets (use '> >')
file_dialog(const std::vector<std::pair<std::string, std::string>> &filetypes,
^~
> >
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:494:65: error: a space is required between consecutive right angle brackets (use '> >')
file_dialog(const std::vector<std::pair<std::string, std::string>> &filetypes,
^~
> >
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/common.h:521:61: error: a space is required between consecutive right angle brackets (use '> >')
extern NANOGUI_EXPORT std::vector<std::pair<int, std::string>>
^~
> >
In file included from /Users/firat/Desktop/dungeon-defense/main.cpp:11:
In file included from /Users/firat/Desktop/dungeon-defense/include/GUI.h:5:
In file included from /Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/nanogui.h:15:
In file included from /Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/widget.h:15:
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/object.h:45:43: error: expected ';' at end of declaration list
void decRef(bool dealloc = true) const noexcept;
^
;
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/object.h:52:30: error: function definition does not declare parameters
mutable std::atomic m_refCount { 0 };
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/object.h:31:30: error: member initializer 'm_refCount' does not name a non-static data member or base class
Object(const Object &) : m_refCount(0) {}
^~~~~~~~~~~~~
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/object.h:34:38: error: use of undeclared identifier 'm_refCount'; did you mean 'getRefCount'?
int getRefCount() const { return m_refCount; };
^~~~~~~~~~
getRefCount
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/object.h:34:9: note: 'getRefCount' declared here
int getRefCount() const { return m_refCount; };
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/object.h:37:29: error: use of undeclared identifier 'm_refCount'
void incRef() const { ++m_refCount; }
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/object.h:87:13: warning: rvalue references are a C++11 extension [-Wc++11-extensions]
ref(ref &&r) noexcept : m_ptr(r.m_ptr) {
^
/Users/firat/Desktop/dungeon-defense/external/nanogui/include/nanogui/object.h:87:17: error: expected ';' at end of declaration list
ref(ref &&r) noexcept : m_ptr(r.m_ptr) {
^
;
fatal error: too many errors emitted, stopping now [-ferror-limit=]
13 warnings and 20 errors generated.
make[3]: *** [CMakeFiles/dungeon-defense.dir/main.cpp.o] Error 1
make[2]: *** [CMakeFiles/dungeon-defense.dir/all] Error 2
make[1]: *** [CMakeFiles/dungeon-defense.dir/rule] Error 2
make: *** [dungeon-defense] Error 2

From what I can understand, it has something to do with the compiler not being c++11.

• I checked that I do have clang with c++11 support when I built some side projects with it.
• I checked that nothing is wrong with nanogui's CMakeFiles.txt that keeps it from using c++11
• I recently added following lines to the main CMakeFiles.txt in case it overrides? (I don't know a lot about CMake as you can see)
  if (POLICY CMP0058)
  cmake_policy(SET CMP0058 NEW)
  endif()
  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")

What do you think about it, what could be the problem? If you need more information let me know!

[svenevs]

Hi @firatyenidunya, in order to use NanoGUI, you need more than just a c++11 capable compiler -- you have to compile with c++11 (or higher).

I checked that nothing is wrong with nanogui's CMakeFiles.txt that keeps it from using c++11

It goes the other way, you have to tell CMake which standard to use. The most platform-agnostic way to do this is at the beginning:

cmake_minimum_required(VERSION 3.1.3)
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)  # not necessary, but encouraged

The 3.1.3 minimum version is important, as that's when CMAKE_CXX_STANDARD was introduced (as far as I can tell). What the second line does is inform CMake to use the right C++11 flag for the current compiler. With clang, this will typically be -std=c++11, but with GCC it may be e.g. -std=gnu++11. The flag depends on the compiler.

So the compiler errors you are seeing are almost certainly because you need to compile your library with C++11.

NOTE: I advise doing it at the beginning because this has to be done before your CMake "target" is created. If the target is created before you set CMAKE_CXX_STANDARD, it will not apply to that target. So for example

# DOES work
set(CMAKE_CXX_STANDARD 11)
add_executable(myExe main.cpp) # compiled with c++11

# does NOT work
add_executable(myExe main.cpp)
set(CMAKE_CXX_STANDARD 11) # does not apply to `myExe`

I recently added following lines to the main CMakeFiles.txt in case it overrides? (I don't know a lot about CMake as you can see)

if (POLICY CMP0058)
  cmake_policy(SET CMP0058 NEW)
endif()
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")

This is independent of the compiler errors you have. In C++ there's something called "ABI", where libc++ comes in is with clang specifically. NanoGUI by default uses libc++ when clang is the compiler, but this shouldn't cause you problems on OSX (if anything, it would be a problem on Linux). Sparing the gory details, if you really want to make sure libc++ is always used with your project, you could mirror what NanoGUI does (with proper citation of course 😉):

1. The following macro is used, I think you can use it in your own project after doing add_subdirectory(nanogui):

   nanogui/CMakeLists.txt

   Lines 53 to 60 in 3e0b2c8

   	macro(CHECK_CXX_COMPILER_AND_LINKER_FLAGS _RESULT _CXX_FLAGS _LINKER_FLAGS)
   	set(CMAKE_REQUIRED_FLAGS ${_CXX_FLAGS})
   	set(CMAKE_REQUIRED_LIBRARIES ${_LINKER_FLAGS})
   	set(CMAKE_REQUIRED_QUIET TRUE)
   	check_cxx_source_runs("int main(int argc, char **argv) { return 0; }" ${_RESULT})
   	set(CMAKE_REQUIRED_FLAGS "")
   	set(CMAKE_REQUIRED_LIBRARIES "")
   	endmacro()

2. Further down, when clang is the compiler:

   nanogui/CMakeLists.txt

   Lines 174 to 192 in 3e0b2c8

   	# Always use libc++ on Clang
   	if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
   	CHECK_CXX_COMPILER_AND_LINKER_FLAGS(HAS_LIBCPP "-stdlib=libc++" "-stdlib=libc++")
   	if (HAS_LIBCPP)
   	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
   	set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -stdlib=libc++")
   	set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -stdlib=libc++")
   	CHECK_CXX_COMPILER_AND_LINKER_FLAGS(HAS_LIBCPPABI "-stdlib=libc++" "-stdlib=libc++ -lc++abi")
   	if(HAS_LIBCPPABI)
   	set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -lc++abi")
   	set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -lc++abi")
   	message(STATUS "NanoGUI: using libc++ and libc++abi.")
   	else()
   	message(STATUS "NanoGUI: using libc++.")
   	endif()
   	else()
   	message(STATUS "NanoGUI: NOT using libc++.")
   	endif()
   	endif()

This would always get triggered for you on OSX unless you are using a non-default compiler.

I hope that helps get you in the right direction :)