[erlang-questions] Building erl_interface with mingw (an unfinished tale)

Davide Marquês <>
Thu Apr 23 05:43:57 CEST 2009


Hi again!

I just did a fresh R13B install on an linux box and came across
the same problem while compiling the erl_interface tutorial example.

If I try this:
    :~/port$ gcc -o extprg erl_comm.c ei.c -lei
-lerl_interface -I/usr/local/lib/erlang/lib/erl_interface-3.6.1/include/
-L/usr/local/lib/erlang/lib/erl_interface-3.6.1/lib/

I get a bunch of "undefined reference" warnings:

/usr/local/lib/erlang/lib/erl_interface-3.6.1/lib//liberl_interface.a(erl_eterm.o):
In function `erl_mk_var':
    /home/nonroot/otp_src_R13B/lib/erl_interface/src/legacy/erl_eterm.c:498:
undefined reference to `__erl_errno_place'
    ... the list continues ...

(I did forgot -lpthread there.)

But if I unpack the contents of libei.a and include the .o files instead of
adding the -lei flag then the linking succeeds and the program works
perfectly:

    :~/port$ gcc -o extprg erl_comm.c ei.c
lib_ei_extracted/*.o -lerl_interface -lpthread
-I/usr/local/lib/erlang/lib/erl_interface-3.6.1/include/
-L/usr/local/lib/erlang/lib/erl_interface-3.6.1/lib/
    :~/port$ erl
    Erlang R13B (erts-5.7.1) [source] [rq:1] [async-threads:0] [hipe]
[kernel-poll:false]

    Eshell V5.7.1  (abort with ^G)
    1> complex:start("./extprg").
    <0.35.0>
    2> complex:foo(1).
    1

What am I missing here? :|
It must be something really trivial but I'm fresh out of ideas on what it
might be.

Cheers,
Davide :)

2009/4/22 Davide Marquês <>

> Hi there!
>
> I was (almost) able to compile erl_interface using mingw (with some
> unhealthy hacks along the way) and I'd like to get your feedback on whether
> this would be the correct way to go.
> Actually, since I have no *useful* experience using gcc and related tools
> I'm prepared to have someone telling me that I really didn't had to
> recompile erl_interface.
> Either way, this might be useful for others that might be thinking of
> taking the same path... :)
>
> My setup: Windows XP, OTP_R13B (I started off with OTP_R13A so paths will
> vary), MSYS + MinGW.
>
> I started off following the erl_interface tutorial (
> http://erlang.org/doc/tutorial/erl_interface.html) and things broke when I
> tried to compile:
>      /c/Projectos/eNotify/src/native/port
>     $ gcc.exe ei.c erl_comm.c -o extprg.exe
> -Ic:/erl5.7/lib/erl_interface-3.6/include
> -Lc:/erl5.7/lib/erl_interface-3.6/lib -lei -lerl_interface
>     Warning: .drectve `/DEFAULTLIB:"uuid.lib" /DEFAULTLIB:"uuid.lib"
> /DEFAULTLIB:"LIBCMT" /DEFAULTLIB:"OLDNAMES" ' unrecognized
>     Warning: .drectve `/DEFAULTLIB:"uuid.lib" /DEFAULTLIB:"uuid.lib"
> /DEFAULTLIB:"LIBCMT" /DEFAULTLIB:"OLDNAMES" ' unrecognized
>     Warning: .drectve `/DEFAULTLIB:"uuid.lib" /DEFAULTLIB:"uuid.lib"
> /DEFAULTLIB:"LIBCMT" /DEFAULTLIB:"OLDNAMES" ' unrecognized
>     Warning: .drectve `/DEFAULTLIB:"uuid.lib" /DEFAULTLIB:"uuid.lib"
> /DEFAULTLIB:"LIBCMT" /DEFAULTLIB:"OLDNAMES" ' unrecognized
>     Warning: .drectve `/DEFAULTLIB:"uuid.lib" /DEFAULTLIB:"uuid.lib"
> /DEFAULTLIB:"LIBCMT" /DEFAULTLIB:"OLDNAMES" ' unrecognized
>
> c:/erl5.7/lib/erl_interface-3.6/lib/erl_interface.lib(C:/cygwin/ldisk/daily_build/otp_build_win32_r13a.2009-03-16_22/otp_src_R13A/lib/erl_interface/
> obj.mt/win32/erl_malloc.o):(.text+0x47<http://obj.mt/win32/erl_malloc.o%29:%28.text+0x47>):
> undefined reference to `ei_malloc'
>
> c:/erl5.7/lib/erl_interface-3.6/lib/erl_interface.lib(C:/cygwin/ldisk/daily_build/otp_build_win32_r13a.2009-03-16_22/otp_src_R13A/lib/erl_interface/
> obj.mt/win32/erl_malloc.o):(.text+0x7c<http://obj.mt/win32/erl_malloc.o%29:%28.text+0x7c>):
> undefined reference to `ei_realloc'
>     (...)
>
>
> c:/erl5.7/lib/erl_interface-3.6/lib/erl_interface.lib(C:/cygwin/ldisk/daily_build/otp_build_win32_r13a.2009-03-16_22/otp_src_R13A/lib/erl_interface/
> obj.mt/win32/erl_error.o):(.text+0xa2<http://obj.mt/win32/erl_error.o%29:%28.text+0xa2>):
> more undefined references to `__iob_func' follow
>     collect2: ld returned 1 exit status
>
> ??? :|
> The ei.lib and erl_interface.lib files were in
> c:/erl5.7/lib/erl_interface-3.6/lib so I was expecting this to work. :\
>
> A little online research (
> http://erlang.org/pipermail/erlang-questions/2003-September/009854.html)
> lead me think that the .lib files weren't GCC-compliant (and what I needed
> were .a files).
> So it would be a simple matter of getting the source and compiling
> erl_interface again (famous last words).
>
> This is were someone can come in and say "No! No! No! You just had to do
> XPTO."
> Considering no XPTO existed I went along to try and build erl_interface.
>
> First I tried to just build it using the files that were available on the
> windows binary distribution but it failed complaining about a missing /make/
> target.mk.
> So I:
>
>    - got the otp_src_R13A sourcecode
>    - did a ./configure
>    - exported ERL_TOP=c:/otp_src_R13A
>    - IIRC
>       - got something about a missing
>       c:/otp_src_R13A/make/i686-pc-mingw32/otp.mk folder
>       - which I copied and renamed from c:/otp_src_R13A/make/otp.mk.in(I'm guessing something is responsible for this step)
>       - added the necessary LIBS = -lwsock32 to
>    c:/otp_src_R13A/lib/erl_interface/src/i686-pc-mingw32/Makefile
>    - did a successful build
>       - which resulted in two files: libei.a and liberl_interface.a
>       getting placed in
>       c:/otp_src_R13A/lib/erl_interface/obj.debug/i686-pc-mingw32/
>       - I created a folder c:/otp_src_R13A/lib/erl_interface/lib
>       - and copied the two files there
>
> I then tried using those two files to build the erl_interface tutorial
> program with this result:
>          /c/Projectos/eNotify/src/native/port
>         $ gcc.exe ei.c erl_comm.c -o extprg.exe
> -Ic:/otp_src_R13A/lib/erl_interface/include
> -Lc:/otp_src_R13A/lib/erl_interface/lib -lei -lerl_interface
>
> c:/otp_src_R13A/lib/erl_interface/lib/liberl_interface.a(erl_malloc.o): In
> function `erl_malloc':
>         c:/otp_src_R13A/lib/erl_interface/src/legacy/erl_malloc.c:221:
> undefined reference to `ei_malloc'
>
> c:/otp_src_R13A/lib/erl_interface/lib/liberl_interface.a(erl_malloc.o): In
> function `erl_realloc':
>         c:/otp_src_R13A/lib/erl_interface/src/legacy/erl_malloc.c:231:
> undefined reference to `ei_realloc'
>
> c:/otp_src_R13A/lib/erl_interface/lib/liberl_interface.a(erl_malloc.o): In
> function `erl_free':
>         c:/otp_src_R13A/lib/erl_interface/src/legacy/erl_malloc.c:238:
> undefined reference to `ei_free'
>         ...
>
> c:/otp_src_R13A/lib/erl_interface/lib/liberl_interface.a(erl_fix_alloc.o):
> In function `erl_eterm_alloc':
>         c:/otp_src_R13A/lib/erl_interface/src/legacy/erl_fix_alloc.c:111:
> undefined reference to `__erl_errno_place'
>         collect2: ld returned 1 exit status
>
> Which (other than the initial warnings) is exactly the same problem as the
> one I got with the original compilation.
> Here I took a look at the build process and realized that the erl_interface
> build process had also produced a bunch of .o files in another folder:
> c:/erl5.7/lib/erl_interface/obj.st.debug/i686-pc-mingw32/
>
> Since the compiler was nagging me about missing .o files I just included
> them all in:
>          /c/Projectos/eNotify/src/native/port
>         $ gcc.exe ei.c erl_comm.c -o extprg.exe
> c:/otp_src_R13A/lib/erl_interface/include/*.o
> -Ic:/otp_src_R13A/lib/erl_interface/include
> -Lc:/otp_src_R13A/lib/erl_interface/lib -lei -lerl_interface -lwsock32
>         c:/otp_src_R13A/lib/erl_interface/include/erl_resolve.o: In
> function `erl_gethostbyname_r':
>         c:/otp_src_R13A/lib/erl_interface/src/legacy/erl_resolve.c:58:
> undefined reference to `ei_gethostbyname_r'
>         c:/otp_src_R13A/lib/erl_interface/include/erl_resolve.o: In
> function `erl_gethostbyaddr_r':
>         c:/otp_src_R13A/lib/erl_interface/src/legacy/erl_resolve.c:70:
> undefined reference to `ei_gethostbyaddr_r'
>         collect2: ld returned 1 exit status
>
> :| This is another struggle.
> Under certain circumstances (mine) the functions ei_gethostbyname_r and
> ei_gethostbyaddr_r aren't included in the compilation of the ei_resolve.c
> file.
> Being completely astray from my original goal, and after figuring out that
> these were the reentrant versions of the same functions without the _r and
> that on windows the original ones are already thread safe (
> http://daniel.haxx.se/projects/portability/), I just went ahead and added
> these *_r functions calling out to original ones (on the $ifdef __WIN32__
> part ). This was the unhealthy hack part. :)
> Of course that worked (to shut the compiler up at least). :P
>      /c/Projectos/eNotify/src/native/port
>     $ gcc.exe ei.c erl_comm.c -o extprg.exe
> c:/otp_src_R13A/lib/erl_interface/include/*.o
> -Ic:/otp_src_R13A/lib/erl_interface/include
> -Lc:/otp_src_R13A/lib/erl_interface/lib -lei -lerl_interface -lwsock32
>
> Finally that got me a working extprg.exe that I was able to complete the
> tutorial with!
>
> <sleep break + upgrade to R13B>
>
> I picked up were I left off: being able to compile IF including all of the
> .o files.
> Some [n00b] research -> http://en.wikipedia.org/wiki/Ar_(Unix)<http://en.wikipedia.org/wiki/Ar_%28Unix%29>&
> http://linux.die.net/man/1/ar
> Got me to check if all the .o files the linker was complaining about were
> getting archived in the two .a files.
> And indeed, all of them were on libei.a.
>
> I unpacked the .o files from libeia.a and replaced it with a call to those
> .o:
>      /c/Projectos/eNotify/src/native/port
>     $ gcc.exe -o extprg.exe ei.c erl_comm.c
> /c/otp_src_R13B/lib/erl_interface/obj/i686-pc-mingw32/*.o
> /c/otp_src_R13B/lib/erl_interface/obj/i686-pc-mingw32/liberl_interface.a
> -Ic:/otp_src_R13B/lib/erl_interface/include -lwsock32
>
> And guess what... It worked! :)
>
> So what am I missing here? Is it normal that "ar"ed files don't link
> correctly? Is it mingw? Or is it just me? :)
> Any(!!!) clues are more than welcome! :)
>
> Cheers,
> Davide :)
>
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