From: Richard Biener <richard.guenther@gmail.com>
To: Fangrui Song <maskray@google.com>
Cc: Alexandre Oliva <oliva@adacore.com>,
GCC Patches <gcc-patches@gcc.gnu.org>,
Nathan Sidwell <nathan@acm.org>,
Joseph Myers <joseph@codesourcery.com>
Subject: Re: [PATCH] Introduce -nolibstdc++ option
Date: Tue, 21 Jun 2022 10:03:47 +0200 [thread overview]
Message-ID: <CAFiYyc1s4kUXQi3XNgx58G6yT9D=OEOOuuyFiBFDRJgp83N+Mw@mail.gmail.com> (raw)
In-Reply-To: <CAFP8O3Jsq88T_EwCtzKADKR-+oJTNszzekjZ78HOABcd_fGxNQ@mail.gmail.com>
On Tue, Jun 21, 2022 at 9:53 AM Fangrui Song <maskray@google.com> wrote:
>
> On Tue, Jun 21, 2022 at 1:43 AM Richard Biener via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > 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.
>
> Is this similar to clang -nostdlib++ ?
> When libstdc++ is selected, clang -nostdlib++ removes -lstdc++.
Probably. Note that we have -static-libstdc++ already so
-nolibstdc++ matches that. We also have -nolibc, not -noclib.
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>
next prev parent reply other threads:[~2022-06-21 8:03 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-21 5:55 Alexandre Oliva
2022-06-21 7:37 ` Richard Biener
2022-06-21 7:53 ` Fangrui Song
2022-06-21 8:03 ` Richard Biener [this message]
2022-06-21 8:19 ` Fangrui Song
2022-06-22 0:36 ` Alexandre Oliva
2022-06-22 18:39 ` Iain Sandoe
2022-06-22 23:28 ` Alexandre Oliva
2022-06-22 23:42 ` Fangrui Song
2022-06-23 11:27 ` Alexandre Oliva
2022-06-24 5:23 ` Alexandre Oliva
2022-09-16 11:52 ` Jason Merrill
2022-09-16 11:53 ` Jason Merrill
2022-11-28 17:56 ` Jason Merrill
2023-02-11 9:09 ` Gerald Pfeifer
2023-03-30 11:23 ` Alexandre Oliva
2023-03-30 13:38 ` Arsen Arsenović
2023-03-30 23:13 ` Gerald Pfeifer
2023-04-06 1:25 ` Alexandre Oliva
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