[PATCH] Check if linker supports -Wl,--undefined-version

[Sam James]

Adhemerval Zanella <adhemerval.zanella@linaro.org> writes:

> Although binutils has supported --no-undefined-version for a long timei
> (319416359200 back in 2002), --undefined-version was only added more
> recently (27fb6a1a7fcd on 2.40).

OK (and sorry for missing it, I should have checked up on that feeling I
had before).

Reviewed-by: Sam James <sam@gentoo.org>

> ---
>  Makerules    |  2 +-
>  configure    | 36 ++++++++++++++++++++++++++++++++++++
>  configure.ac |  6 ++++++
>  3 files changed, 43 insertions(+), 1 deletion(-)
>
> diff --git a/Makerules b/Makerules
> index caa1e43faa..89ef44d7c5 100644
> --- a/Makerules
> +++ b/Makerules
> @@ -510,7 +510,7 @@ map-file = $(firstword $($(@F:.so=-map)) \
>  				   $(filter $(@F:.so=.map),$(version-maps))))
>  # The map version is created with multiple symbols that might not be
>  # exported depending of the ABI.
> -load-map-file = $(map-file:%=-Wl,--version-script=%) -Wl,--undefined-version
> +load-map-file = $(map-file:%=-Wl,--version-script=%) $(have-undefined-version)
>  endif
>  
>  # Compiler arguments to use to link a shared object with libc and
> diff --git a/configure b/configure
> index 1999d12f44..d5bd639586 100755
> --- a/configure
> +++ b/configure
> @@ -9246,6 +9246,42 @@ printf "%s\n" "$libc_linker_feature" >&6; }
>  config_vars="$config_vars
>  have-ld-gcs = $libc_cv_ld_gcs"
>  
> +
> +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for linker that supports --undefined-version" >&5
> +printf %s "checking for linker that supports --undefined-version... " >&6; }
> +libc_linker_feature=no
> +cat > conftest.c <<EOF
> +int _start (void) { return 42; }
> +EOF
> +if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
> +		  -Wl,--undefined-version -nostdlib -nostartfiles
> +		  -fPIC -shared -o conftest.so conftest.c
> +		  1>&5'
> +  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> +  (eval $ac_try) 2>&5
> +  ac_status=$?
> +  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> +  test $ac_status = 0; }; }
> +then
> +  if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp -Wl,--undefined-version -nostdlib \
> +      -nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \
> +      | grep "warning: --undefined-version ignored" > /dev/null 2>&1; then
> +    true
> +  else
> +    libc_linker_feature=yes
> +  fi
> +fi
> +rm -f conftest*
> +if test $libc_linker_feature = yes; then
> +  libc_cv_ld_undefined_version=-Wl,--undefined-version
> +else
> +  libc_cv_ld_undefined_version=
> +fi
> +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5
> +printf "%s\n" "$libc_linker_feature" >&6; }
> +config_vars="$config_vars
> +have-undefined-version = $libc_cv_ld_undefined_version"
> +
>  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if we can build programs as PIE" >&5
>  printf %s "checking if we can build programs as PIE... " >&6; }
>  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> diff --git a/configure.ac b/configure.ac
> index 46a354dfbc..aaf686494a 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -2066,6 +2066,12 @@ LIBC_LINKER_FEATURE([-z gcs=always], [-Wl,-z,gcs=always],
>  		    [libc_cv_ld_gcs=yes], [libc_cv_ld_gcs=no])
>  LIBC_CONFIG_VAR([have-ld-gcs], [$libc_cv_ld_gcs])
>  
> +
> +LIBC_LINKER_FEATURE([--undefined-version], [-Wl,--undefined-version],
> +		    [libc_cv_ld_undefined_version=-Wl,--undefined-version],
> +		    [libc_cv_ld_undefined_version=])
> +LIBC_CONFIG_VAR([have-undefined-version], [$libc_cv_ld_undefined_version])
> +
>  AC_MSG_CHECKING(if we can build programs as PIE)
>  AC_COMPILE_IFELSE([AC_LANG_SOURCE([[#ifdef PIE_UNSUPPORTED
>  # error PIE is not supported