[arch-general] Issue linking 32-bit GAS assembly

[Dutch Ingraham]

On Wed, Oct 17, 2018 at 08:14:48PM -0700, Anatol Pomozov via arch-general wrote:
> Hello
> On Wed, Oct 17, 2018 at 12:37 PM Dutch Ingraham <stoa at gmx.us> wrote:
> >
> > Hi all:
> >
> > I'm having a problem linking 32-bit GAS assembly code that references external
> > C libraries on an up-to-date 64-bit Arch installation.
> >
> > I have enabled the 32-bit repositories and installed the multilib-devel group
> > and lib32-glibc. I have updated the library cache with ldconfig and rebooted.
> >
> > The command to assemble is: <as --32 -o filename.o filename.s>.  Assembly
> > succeeds.
> >
> > However, when linking using the command
> > <ld -melf_i386 --dynamic-linker /lib32/ld-linux.so.2 -lc -o filename filename.o>
> >
> > the command fails with:
> >         ld: skipping incompatible /usr/lib/libc.so when searching for -lc
> >         ld: skipping incompatible /usr/lib/libc.a when searching for -lc
> >         ld: cannot find -lc
> >
> > Note this linker command (or a hierarchy-appropriate one) seems standard, and
> > succeeds on a 64-bit Debian OS.
> >
> > There is a fairly recent Forum question (but pre-dating the discontinuance of
> > i686 support) regarding the same issue at
> > https://bbs.archlinux.org/viewtopic.php?id=229235 which indicates the command
> > should be:
> >
> > <ld -melf_i386 -shared -L /usr/lib32 -dynamic-linker /lib/ld-linux.so.2 -o \
> > filename filename.o -lc>
> >
> > This command succeeds, insofar as the linker returns an exit code of 0. However,
> > running the program (and all other similar programs) fails with "Illegal
> > instruction (core dumped)." Assembling with debugging symbols and running a
> > backtrace didn't enlighten me.
> >
> > Note that changing /lib/ld-linux to /usr/lib32/ld-linux in the command immediately
> > above produces the same result, as confirmed by the output of <ldconfig -p>
> >
> > Anyone see something I've missed of have any suggestions?  Thanks.
> >
> >
> > -----------
> >
> > Here is some simple code to test with:
> >
> >
> > # paramtest2.s - Listing system environment variables
> > .section .data
> > output:
> >    .asciz "%s\n"
> > .section .text
> > .globl _start
> > _start:
> >    movl %esp, %ebp
> >    addl $12, %ebp
> > loop1:
> >    cmpl $0, (%ebp)
> >    je endit
> >    pushl (%ebp)
> >    pushl $output
> >    call printf
> >    addl $12, %esp
> >    addl $4, %ebp
> >    loop loop1
> > endit:
> >    pushl $0
> >    call exit
> 
> 
> Here is what I ran to make your example working on my Arch Linux machine
> 
> 
> sudo pacman -S lib32-glibc
> as --32 -o asm.o asm.s
> ld -melf_i386 --dynamic-linker /lib/ld-linux.so.2 -L/usr/lib32 -lc -o asm asm.o
> ./asm
> 
> 
> The only difference that I specified -L (library search path) to make
> sure the linked can find 32-bit version of libc.

Hi Anatol:

I was able assemble and link with gcc, then look at the library paths
used with ldd.

Actually, your command is the same as the command above, minus the
'shared' option, from the Forum post.  That command was core dumping for
me; not sure how it was working for them.

Thanks for your help; your command works fine.