[erlang-questions] Problems with C Erlang interface

J Bhanot <>
Wed Jan 30 14:26:10 CET 2008


Hi,

Got the solution :

to compile :  gcc -c 
-I/usr/local/lib/erlang/lib/erl_interface-3.5.5.3/include test.c
to link :  gcc -L/usr/local/lib/erlang/lib/erl_interface-3.5.5.3/lib/ 
test.o -lerl_interface -lei -lpthread -o test'
to execute : ./test 

:-)

Thanks,
jb

____________________________________________



"Jachym Holecek" <> 
01/30/2008 06:39 PM

To
"J Bhanot" <>, "Tomas Pihl" <>
cc

Subject
Re: [erlang-questions] Problems with C Erlang interface






On Wed, 30 Jan 2008 13:09:43 +0100, J Bhanot <> wrote:
> [ otp_src_R12B-0]# cc -o test
> -I/usr/local/lib/erlang/lib/erl_interface-3.5.5.3/include
> -L/usr/local/lib/erlang/lib/erl_interface-3.5.5.3/lib -lerl_interface 
> -lei
> test.c
>
> got the following error -
>
> /tmp/ccAvr8jd.o: In function `main':
> test.c:(.text+0x28): undefined reference to `erl_init'
> collect2: ld returned 1 exit status
> [ otp_src_R12B-0]#

To quote gcc(1):

   [explanation of '-l' option]
   It makes a difference where in the command you write this option; the 
linker searches and processes
   libraries and object files in the order they are specified.  Thus, 
foo.o 
-lz bar.o searches library
   z after file foo.o but before bar.o.  If bar.o refers to functions in 
z, 
those functions may not be
   loaded.

So you might try to put the arguments in different order:

   [ otp_src_R12B-0]# cc -o test \
   -I/usr/local/lib/erlang/lib/erl_interface-3.5.5.3/include \
   -L/usr/local/lib/erlang/lib/erl_interface-3.5.5.3/lib \
   test.c \
   -lerl_interface \
   -lei

(FWIW the 'erl_init' symbol is defined in liberl_interface.a)

> Also, i tried
>
> [ otp_src_R12B-0]# ld
> -L/usr/local/lib/erlang/lib/erl_interface-3.5.5.3/lib test.o
> -lerl_interface -lei -lpthread -o test

Using ld(1) requires you to know exactly what you're doing. Normally,
you want to let [g]cc(1) compile & link your program (it will invoke ld(1)
internally with the correct options).

HTH,
     -- Jachym


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