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

[Maarten de Vries]

Why not let gcc take care of what compiler/assembler and linker to 
invoke with which precise flags:

$ gcc -m32 -o foo filename.s
$ ./foo # great success!

It will probably link to libc without you even asking for it. And if 
that works and you really want to know what linker flags you need, you 
can add -v to make gcc spam you about it.


-- Maarten

(Sent off-list by accident before, sending to the list now.)


On 10/17/18 9:36 PM, Dutch Ingraham 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