How To Call D Code from Objective C?

[Mike McKee via Digitalmars-d]

So I'm having trouble figuring out the D and C code.

Created dfunc.d with this:

extern (C) string dfunc(string s) {
         return s ~ "response";
}

Then compiled:

$ dmd -c dfunc.d

This created dfunc.o without error.

Next, I created C code like so:

extern char * dfunc(char *);
char * c_dfunc(char *s) {
   return dfunc(s);
}

But when I try to compile on Linux (as a test -- I could have 
done this slightly differently on OSX), it throws this error:

$ gcc -dynamiclib -o cfunc.o cfunc.c dfunc.o -L/usr/local/lib 
-lphobos2 -lpthread -lm
cc1: warning: unrecognized gcc debugging option: y [enabled by 
default]
cc1: warning: unrecognized gcc debugging option: n [enabled by 
default]
cc1: warning: unrecognized gcc debugging option: m [enabled by 
default]
cc1: warning: unrecognized gcc debugging option: i [enabled by 
default]
cc1: warning: unrecognized gcc debugging option: c [enabled by 
default]
cc1: warning: unrecognized gcc debugging option: l [enabled by 
default]
cc1: warning: unrecognized gcc debugging option: i [enabled by 
default]
cc1: warning: unrecognized gcc debugging option: b [enabled by 
default]
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 0 has invalid symbol index 11
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 1 has invalid symbol index 12
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 2 has invalid symbol index 2
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 3 has invalid symbol index 2
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 4 has invalid symbol index 11
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 5 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 6 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 7 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 8 has invalid symbol index 12
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 9 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 10 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 11 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 12 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 13 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 14 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 15 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 16 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 17 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 18 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 19 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 20 has invalid symbol index 13
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_info): 
relocation 21 has invalid symbol index 22
/usr/bin/ld: 
/usr/lib/debug/usr/lib/i386-linux-gnu/crt1.o(.debug_line): 
relocation 0 has invalid symbol index 2
/usr/lib/gcc/i686-linux-gnu/4.8/../../../i386-linux-gnu/crt1.o: 
In function `_start':
(.text+0x18): undefined reference to `main'
collect2: error: ld returned 1 exit status