Re: [PATCH] configure: do not require gcc runtime library for firmwares

[Michael Tokarev]

16.02.2024 21:12, Marek Marczykowski-Górecki :
> probe_target_compiler() when checking for multilib support checks if
> -nostdlib works together with -lgcc. It isn't necessary for building
> various components in pc-bios/optionrom, as evidenced by looking at
> actually used link flags there.
> Alpine Linux for x86_64 does not ship with 32bit libgcc, but its gcc is
> otherwise perfectly capable of building firmwares in pc-bios/optionrom
> dir. Make configure recognize this situation.

This is exactly the same situation as I faced on debian.  However it was
easy to work around in debian, - there, there's an i386 cross-compiler
available, which is found automatically by the current ./configure just
fine, and it is named the same way on debian and fedora for example.

> Keep requiring functional -lgcc in other places.
>
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> ---
>   configure | 10 +++++++---
>   1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/configure b/configure
> index ff058d6c48..7721999f49 100755
> --- a/configure
> +++ b/configure
> @@ -1216,7 +1216,7 @@ have_target() {
>     return 1
>   }
>   
> -# probe_target_compiler TARGET
> +# probe_target_compiler TARGET [nostdlib-extra-ldflags]
>   #
>   # Look for a compiler for the given target, either native or cross.
>   # Set variables target_* if a compiler is found, and container_cross_*
> @@ -1226,6 +1226,9 @@ have_target() {
>   #
>   # If TARGET is a user-mode emulation target, also set build_static to
>   # "y" if static linking is possible.
> +# When testing -nostdlib build, -lgcc will be added for more extensive multilib
> +# support test, but the -lgcc can be overriden with the second argument to the
> +# function.
>   #
>   probe_target_compiler() {
>     # reset all output variables
> @@ -1243,6 +1246,7 @@ probe_target_compiler() {
>     container_cross_strip=
>   
>     target_arch=${1%%-*}
> +  nostdlib_ldflags=${2--lgcc}

This is a) difficult to follow, and b) difficult to override too,
if we don't need any options besides removing -lgcc (like using " "
which will be removed by the shell down the line).  At the very
least this ${..} is better to be written in double quotes, to allow
more options in one arg.

Maybe it's better to do it other way around?  Like, to pass additional
options required for -nostdlib case, including -lgcc, in the places where
it is actually required?

Also, I'd use an option here, - positional parameter is definitely too
difficult to follow.  Like

  probe_target_compiler [-nostdlib-ldflags=foo] TARGET

  nostdlib_ldflags=
  case "$1" in
    -nostdlib-ldflags=*) nostdlib_ldflags="${1#*=}"; shift;;
  esac

>     case $target_arch in
>       aarch64) container_hosts="x86_64 aarch64" ;;
>       alpha) container_hosts=x86_64 ;;
> @@ -1432,7 +1436,7 @@ probe_target_compiler() {
>       case $1 in
>         *-softmmu)
>           if do_compiler "$target_cc" $target_cflags -o $TMPO -c $TMPC &&
> -          do_compiler "$target_cc" $target_cflags -r -nostdlib -o 
> "${TMPDIR1}/${TMPB}2.o" "$TMPO" -lgcc; then
> +          do_compiler "$target_cc" $target_cflags -r -nostdlib -o 
> "${TMPDIR1}/${TMPB}2.o" "$TMPO" $nostdlib_ldflags; then
>             got_cross_cc=yes
>             break
>           fi
> @@ -1544,7 +1548,7 @@ echo "# Automatically generated by configure - do not 
> modify" > Makefile.prereqs
>   if have_target i386-softmmu x86_64-softmmu && \
>           test "$host_os" != "darwin" && test "$host_os" != "sunos" && \
>           test "$host_os" != "haiku" && \
> -        probe_target_compiler i386-softmmu; then
> +        probe_target_compiler i386-softmmu ""; then
>       subdirs="$subdirs pc-bios/optionrom"
>       config_mak=pc-bios/optionrom/config.mak
>       echo "# Automatically generated by configure - do not modify" > 
> $config_mak