From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-x72b.google.com (mail-qk1-x72b.google.com [IPv6:2607:f8b0:4864:20::72b]) by sourceware.org (Postfix) with ESMTPS id 90DAD384144C for ; Tue, 21 Jun 2022 08:03:59 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 90DAD384144C Received: by mail-qk1-x72b.google.com with SMTP id d23so9483135qke.0 for ; Tue, 21 Jun 2022 01:03:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=+huzy1pEGPDasRIT2MZeg1JGy+yG9DFRPDIWSJpu4lM=; b=IVEI9KO707udaZvOPXKNT6WRO48d6dEdkke6HZKUdAU+l2UJsvWFjAhDIyjFlfQ7Cu j6qPYLvYajwA91+uxwYQeoPdkPJZSGoSWWYeDhnE7VZDaHCm9nvJ3efDV94mueBIS69B 0PYJDQY37vgWCIZY/egKIdjF1ZW0EktTdVv4+/t8gnoGJLhaH8Fo5gaQ+XSNbgsiDSix g/Y5RoOI3lN74iooTkK4EpcpmEWGJIrwzxzDjqA+V4Uj06MPSNdyFCP9T+lerEdxHPAp D/lnRz2HGcsaADAaxP/qJlEfRNPIlyOI4m2+xrLWYObImmKg5LspnGog5Qbox5jaNSSV RZAw== X-Gm-Message-State: AJIora+EuwutwBVGLSiURQJDiIOCwD8MUj3NJ0pomk9O/lab9vVxSB4w AJm7EOWsvzK0fJb0m2mE1+zMEAGarG+PlXbg0Ms= X-Google-Smtp-Source: AGRyM1trNWxWbKS6DIVgbyurqWFtelE2zErp5QQdq/WlQX7Kmp2FmaPhCw3gI6gK8g0hhGBFA+z3bKyjMLYiguYfq7I= X-Received: by 2002:a05:620a:16d4:b0:6a6:b1cd:4f71 with SMTP id a20-20020a05620a16d400b006a6b1cd4f71mr18922125qkn.581.1655798638912; Tue, 21 Jun 2022 01:03:58 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Richard Biener Date: Tue, 21 Jun 2022 10:03:47 +0200 Message-ID: Subject: Re: [PATCH] Introduce -nolibstdc++ option To: Fangrui Song Cc: Alexandre Oliva , GCC Patches , Nathan Sidwell , Joseph Myers Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-8.0 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 21 Jun 2022 08:04:05 -0000 On Tue, Jun 21, 2022 at 9:53 AM Fangrui Song wrote: > > On Tue, Jun 21, 2022 at 1:43 AM Richard Biener via Gcc-patches > wrote: > > > > On Tue, Jun 21, 2022 at 7:56 AM Alexandre Oliva via Gcc-patches > > 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. 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