On Tue, Jun 21, 2022 at 7:56 AM Alexandre Oliva via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
>
> Using g++ to link without libstdc++, as in g++.dg/abi/pure-virtual1.C,
> is error prone, because there's no way to tell g++ to drop libstdc++
> without also dropping libc and any other libraries that the target
> implicitly links in.
>
> This has often led to the need for manual adjustments to this
> testcase.
>
> I figured adding support for -nolibstdc++, even though redundant,
> makes some sense. One could presumably use gcc rather than g++ for
> linking, for the same effect, but sometimes changing the link command
> is harder than adding an option, as in our testsuite.
>
> Regstrapped on x86_64-linux-gnu, also tested with a cross to
> aarch64-rtems6. Ok to install?
OK in case nobody objects in 24h.
Richard.
>
> for gcc/ChangeLog
>
> * common.opt (nolibstdc++): New.
> * doc/invoke.texi (-nolibstdc++): Document it.
>
> for gcc/cp/ChangeLog
>
> * g++spec.c (lang_specific_driver): Implement -nolibstdc++.
>
> for gcc/testsuite/ChangeLog
>
> * g++.dg/abi/pure-virtual1.C: Use -nolibstdc++.
> ---
> gcc/common.opt | 3 +++
> gcc/cp/g++spec.cc | 1 +
> gcc/doc/invoke.texi | 6 +++++-
> gcc/testsuite/g++.dg/abi/pure-virtual1.C | 2 +-
> 4 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/gcc/common.opt b/gcc/common.opt
> index 32917aafcaec1..e00c6fc2fb098 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -3456,6 +3456,9 @@ Driver
> nolibc
> Driver
>
> +nolibstdc++
> +Driver
> +
> nostdlib
> Driver
>
> diff --git a/gcc/cp/g++spec.cc b/gcc/cp/g++spec.cc
> index 8174d652776b1..539e6ca089d85 100644
> --- a/gcc/cp/g++spec.cc
> +++ b/gcc/cp/g++spec.cc
> @@ -160,6 +160,7 @@ lang_specific_driver (struct cl_decoded_option
> **in_decoded_options,
> {
> case OPT_nostdlib:
> case OPT_nodefaultlibs:
> + case OPT_nolibstdc__:
> library = -1;
> break;
>
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 50f57877477bc..469b6d97e0dfa 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -652,7 +652,7 @@ Objective-C and Objective-C++ Dialects}.
> @item Linker Options
> @xref{Link Options,,Options for Linking}.
> @gccoptlist{@var{object-file-name} -fuse-ld=@var{linker} -l@var{library}
> @gol
> --nostartfiles -nodefaultlibs -nolibc -nostdlib @gol
> +-nostartfiles -nodefaultlibs -nolibc -nolibstdc++ -nostdlib @gol
> -e @var{entry} --entry=@var{entry} @gol
> -pie -pthread -r -rdynamic @gol
> -s -static -static-pie -static-libgcc -static-libstdc++ @gol
> @@ -16787,6 +16787,10 @@ absence of a C library is assumed, for example
> @option{-lpthread} or
> @option{-lm} in some configurations. This is intended for bare-board
> targets when there is indeed no C library available.
>
> +@item -nolibstdc++
> +@opindex nolibstdc++
> +Do not link with standard C++ libraries implicitly.
> +
> @item -nostdlib
> @opindex nostdlib
> Do not use the standard system startup files or libraries when linking.
> diff --git a/gcc/testsuite/g++.dg/abi/pure-virtual1.C
> b/gcc/testsuite/g++.dg/abi/pure-virtual1.C
> index 538e2cb097a0d..889c33e4952f4 100644
> --- a/gcc/testsuite/g++.dg/abi/pure-virtual1.C
> +++ b/gcc/testsuite/g++.dg/abi/pure-virtual1.C
> @@ -1,7 +1,7 @@
> // Test that we don't need libsupc++ just for __cxa_pure_virtual.
> // { dg-do link }
> // { dg-require-weak }
> -// { dg-additional-options "-fno-rtti -nodefaultlibs -lc" }
> +// { dg-additional-options "-fno-rtti -nolibstdc++" }
> // { dg-additional-options "-Wl,-undefined,dynamic_lookup" { target
> *-*-darwin* } }
> // { dg-xfail-if "AIX weak" { powerpc-ibm-aix* } }
>
>
> --
> Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
> Free Software Activist GNU Toolchain Engineer
> Disinformation flourishes because many people care deeply about injustice
> but very few check the facts. Ask me about <https://stallmansupport.org>
