Re: Help with static linking

[Kip Warner]

On Mon, 2013-06-03 at 17:06 -0400, Paul Smith wrote:
> I can't think of any reason why adding those flags would cause this to
> happen.  Indeed, I can't think of any reason why ld-linux.so would NOT
> be linked with your application before these flags were added.  I would
> have thought that any executable that had any dynamic libraries linked
> at all would need this (it's the runtime linker).

Who knows. I can't seem to explain it either. =P

> Are you sure that library didn't used to exist in the ldd output?  If
> so, were you linking your executable statically (no shared libs) before?

This is what I see when I run ./configure --enable-dbus-interface &&
make && objdump -p ./viking-extractor

...
Dynamic Section:
  NEEDED               libgio-2.0.so.0
  NEEDED               libgobject-2.0.so.0
  NEEDED               libglib-2.0.so.0
  NEEDED               libpng12.so.0
  NEEDED               libzzip-0.so.13
  NEEDED               libstdc++.so.6
  NEEDED               libm.so.6
  NEEDED               libgcc_s.so.1
  NEEDED               libpthread.so.0
  NEEDED               libc.so.6
...

And with --enable-static appended to ./configure...

...
Dynamic Section:
  NEEDED               libgio-2.0.so.0
  NEEDED               libgobject-2.0.so.0
  NEEDED               libglib-2.0.so.0
  NEEDED               libm.so.6
  NEEDED               libpthread.so.0
  NEEDED               libc.so.6
  NEEDED               ld-linux-x86-64.so.2
...

I should add that I defined some logic for --enable-static in
configure.ac as such...

    # D-Bus interface...
    AC_ARG_ENABLE([static],
        [AS_HELP_STRING([--enable-static],
            [enable static compilation @<:@default: no@:>@])],
        [static=${enableval}], 
        [static=no])

...

# zziplib...

    # Check for C header and library...
    if test "$static" = yes; then
        PKG_CHECK_MODULES_STATIC([libzzip], [zziplib], [have_zzip=yes], 
[have_zzip=no])
    else
        PKG_CHECK_MODULES([libzzip], [zziplib], [have_zzip=yes], [have_zzip=no])
    fi
    if test "x${have_zzip}" = xno; then
        AC_MSG_ERROR([zziplib runtime library is required, but was not 
detected...])
    fi

    # Store the needed compiler flags for automake since this doesn't happen
    #  automatically like with AC_CHECK_LIB. We will take care of linker
    #  flags later...
    CXXFLAGS="$CXXFLAGS $libzzip_CFLAGS"

# Portable network graphics...

    # Check for C++ interface header...
    AC_CHECK_HEADERS([png++/png.hpp], [have_png_cxx=yes], [have_png_cxx=no])
    if test "x${have_png_cxx}" = xno; then
        AC_MSG_ERROR([libpng++ headers are required, but were not detected...])
    fi

    # Check for C header and static library...
    if test "$static" = yes; then
        PKG_CHECK_MODULES_STATIC([libpng], [libpng], [have_png=yes], 
[have_png=no])
    else
        PKG_CHECK_MODULES([libpng], [libpng], [have_png=yes], [have_png=no])
    fi
    if test "x${have_png}" = xno; then
        AC_MSG_ERROR([libpng runtime library is required, but was not 
detected...])
    fi

    # Store the needed compiler flags for automake since this doesn't happen
    #  automatically like with AC_CHECK_LIB. We will take care of linker
    #  flags later...
    CXXFLAGS="$CXXFLAGS $libpng_CFLAGS"

...

# Set additional linker flags...

    # If static compilation is enabled, update linker...
    if test "$static" = yes; then
        
        # libpng and libzzip statically link against...
        LIBS="$LIBS -Wl,-Bstatic $libpng_LIBS $libzzip_LIBS -Wl,-Bdynamic"

        # Static linking against GCC's runtimes and the standard C++ library...
        LDFLAGS="$LDFLAGS -static-libgcc -static-libstdc++"

    # Otherwise insert vanilla linker flags...
    else
        LIBS="$LIBS $libpng_LIBS $libzzip_LIBS"
    fi

...

# If static compilation is enabled, update linker...
if test "$static" = yes; then
    
    # libpng and libzzip statically link against...
    LIBS="$LIBS -Wl,-Bstatic $libpng_LIBS $libzzip_LIBS -Wl,-Bdynamic"

    # Static linking against GCC's runtimes and the standard C++ library...
    LDFLAGS="$LDFLAGS -static-libgcc -static-libstdc++"

# Otherwise insert vanilla linker flags...
else
    LIBS="$LIBS $libpng_LIBS $libzzip_LIBS"
fi

So that's the solution I've come up with so far and it seems to work,
but I'm open to better solutions.

> Anyway, seeing that library doesn't bother me.
> 
> > I wonder if I could do this for a GNU/Linux i386 binary and amd64, and a
> > w32 binary via mingw sysroot, if such a thing is possible.
> 
> It is certainly possible to create a cross-compilation environment to
> build Windows/mingw output on a Linux system; indeed it's becoming a
> very popular way of handling Windows targets.  Some google searching
> will lead you to many examples and write-ups; I don't have anything
> handy that I've tried and can attest to unfortunately.
> 
> However, it WON'T be as simple as you describe above.  Just having a
> different sysroot won't be enough: you'll have to actually create a
> separate cross-compiler toolchain as well.  That's because all the
> Linux-based distributions use the same basic executable layout, calling
> structure, etc. (ELF).  So, the only real difference from a compiler
> standpoint between Red Hat, Debian, etc. are the versions of the various
> shared libraries that are installed.

Alright. Noted.

> Windows, on the other hand uses an entirely different layout for its
> executables and libraries.  It's far more than just some library version
> differences: you need a whole different compiler.

Thankfully it looks as though there are precompiled MinGW debs available
for my distribution (Ubuntu Raring / amd64) and hopefully I'll be able
to get them up and running.

-- 
Kip Warner -- Software Engineer
OpenPGP encrypted/signed mail preferred
http://www.thevertigo.com

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