Error when installing FLTK 1.3.3 on mac OS X 10.10

Question

So I am trying to install FLTK on my mac OS X 10.10. I follow the README.OSX.txt file, but when I get to actually installing it on the make command, I get the following error and warning:

Fl_cocoa.mm:4080:5: error: unknown type name 'NSOperatingSystemVersion'
    NSOperatingSystemVersion version = [[NSProcessInfo processInfo] operatingSystemVersion];
    ^
Fl_cocoa.mm:4080:69: warning: instance method '-operatingSystemVersion' not found (return type defaults to 'id') [-Wobjc-method-access]
    NSOperatingSystemVersion version = [[NSProcessInfo processInfo] operatingSystemVersion];
                                                                    ^~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSProcessInfo.h:20:12: note: 
      receiver is instance of class declared here
@interface NSProcessInfo : NSObject {

Does anyone have any idea what is causing this error or anything that I could do to fix it? Thanks!

Answer 1

First go to the fltk-1.3.3 folder and type export CXX=c++. This will tell the compiler to use Clang++ to compile FLTK. Then type ./configure and sudo make install. That's it. After this, you might want to check if FLTK is properly installed by typing fltk-config --version and to if it gives 1.3.3.