Re: [Caml-list] static linking

["Török Edwin" <edwin+ml-ocaml@etorok.net>]

On 06/06/2014 06:43 PM, Andreea Costea wrote:
> Hi,
> 
> I'm trying to build a rather big system written in Ocaml, using
> ocamlbuild. I managed to set all the needed flags nicely, so that the
> resulted binaries can run on any Unix machine,

I assume you mean any Linux machine on same architecture, or are you thinking
about something like FatELF?

> independent on their
> Ocaml distribution. However, on certain machines I have problems with
> the compatibility between the C libraries. Hence, I tried using
> "-ccopt -static"  for the -lflags and -cflags, respectively, in order
> to produce the desired statically linked binaries while building the
> project. Unfortunately, this attempt leads to the following error:
> 
> "/usr/bin/ld: dynamic STT_GNU_IFUNC symbol `cos' with pointer
> equality in
> `/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../x86_64-linux-gnu/libm.a(s_sin.o)'
> can not be used when making an executable; recompile with -fPIE and
> relink with -pie"

I don't get such an error for 'cos' on Debian, what distro do you use?

> 
> Does this mean I need to recompile the gcc libraries using -pie? Or
> does it mean I am using the wrong method to build the standalone
> executable? Any recommendation to modify the building process (i
> would prefer to use ocambuild)?
> 
> Your answer is much appreciated, Andreea

Static linking will cause troubles if you use gethostbyname or other functions from the Unix module.
Glibc gives warnings like these when linking:
/usr/lib/ocaml/libunix.a(getaddrinfo.o): In function `unix_getaddrinfo':
(.text+0x241): warning: Using 'getaddrinfo' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/ocaml/libunix.a(gethost.o): In function `unix_gethostbyaddr':
(.text+0x1b6): warning: Using 'gethostbyaddr_r' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking

One alternative would be to use http://www.musl-libc.org/, see here on how to do that with opam:
http://www.donadeo.net/post/2014/installing-opam-1-1-1-on-a-cenos-6-5#commentary

Note that you'll have to recompile any C library that you use, besides the already provided libc and libm, with musl-gcc.
If 4.01.0+musl+static doesn't work for you, then try 4.01.0+musl, and use -ccopt -static just when linking the final executable.

Best regards,
--Edwin