On Wed, Oct 17, 2018 at 9:37 PM Dutch Ingraham <stoa@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

Silly question perhaps but does that file actually exist, /lib32/ld-linux.so.2? I haven't set up 32 bit etc and that file doesn't exist on my machine, and I get the exact same errors as you.

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

On 10/17/18 3:36 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.

So, this is magical, why do you think it's supposed to work? Since Arch isn't Debian, the first major issue is it violates the hierarchy... and you didn't fix it, because there is no /lib32. Second issue: the *error* it is showing is that it cannot find a libc.so/libc.a, so the question you should be asking yourself is, what's the search path? Apparently, the default search path on Debian works, but here on Arch, /usr/lib32 is not in fact in the search path. Fix those two problems and it compiles fine, and runs too. But no.....

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.

This fixes both problems, therefore it compiles cleanly. But it also adds the "-shared" flag, which you have not asked yourself why you are using it. Did you read the manpage for this? -shared Create a shared library. This is currently only supported on ELF, XCOFF and SunOS platforms. On SunOS, the linker will automatically create a shared library if the -e option is not used and there are undefined symbols in the link. ... Think, then do. -- Eli Schwartz Bug Wrangler and Trusted User