Compiling on Windows and Mac with Autotool

Question

I have a problem trying to use autotools for a simple contrived project, the task is simple, use Objective-C on Mac OSX, and C++ on Windows (mingw) - with some C glue in the middle.

The project is structured like so (minus all the automatically generated files):

    ./aclocal.m4
    ./configure
    ./configure.ac
    ./Makefile.am
    ./src/darwin/greet.m
    ./src/greet.h
    ./src/main.cpp
    ./src/Makefile.am
    ./src/mingw32/greet.cpp    

The contents of the key files are here on github in a gist. (didn't want to spam here)

I'm using the following command between changes:

$ autoreconf -vis && ./configure && make

The error I receive is full output (here in another gist):

....
Making all in src
g++  -g -O2   -o greetings main.o  
Undefined symbols:
  "greet()", referenced from:
      _main in main.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
make[1]: *** [greetings] Error 1
make: *** [all-recursive] Error 1

I'm very new to autotools, and have come a long way with the help of a couple of good people on IRC, but I think I'm making a conceptual mistake here, really hope there's a simple mistake I am making.

It was my understanding from the docs that EXTRA_progname_SOURCES should contain all possible files, and that the conditionals which are setup should work to select the correct ones.

Alarmingly, I don't think my makefiles are being remade, because even when I change the line in src/Makefile.am to include the sources explicitly for my platform (which is Max OS X Darwin, most of the time) -- the output remains completely the same.

Answer 1

g++ -g -O2 -o greetings main.o

This line tries to build greetings executable from main.o. If greet() function is defined in some other file, for example, greet.cpp, it should be:

++ -g -O2 -o greetings main.o greet.o

Possibly, this line from Makefile.am

greetings_SOURCES = main.cpp greet.h

should be something like this:

greetings_SOURCES = main.cpp greet.cpp

In Makefile.am you have:

if OS_DARWIN  
greetings_SOURCES += darwin/greet.mm
endif
if OS_MINGW32  
greetings_SOURCES += mingw32/greet.cpp
endif

This is the place which is not executed properly. You need to check it.

Answer 2

I see that you're referring to greet.mm in the gist, but greet.m in the question. Automake does not appear to natively support Objective-C++ code. For Objective-C code, you need to have AC_PROG_OBJC in your configure.ac. If you really meant Objective-C++ code, you'll need to do this via a suffix rule.