From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yw1-x112f.google.com (mail-yw1-x112f.google.com [IPv6:2607:f8b0:4864:20::112f]) by sourceware.org (Postfix) with ESMTPS id DCCB23857B98 for ; Tue, 21 Jun 2022 07:53:46 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org DCCB23857B98 Received: by mail-yw1-x112f.google.com with SMTP id 00721157ae682-317710edb9dso122467107b3.0 for ; Tue, 21 Jun 2022 00:53:46 -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=37M7sxLDfKOkUk3W9WuOwAK7W3leblHYU/0UlgBiooQ=; b=eEdVi7woACLf3AW242qMQQVHpGZE5u8o++GLnJc8YBjpRPfa3NA/YWvjPtF8dYT+gw UstDH2YniQwD9LGdnoHnWKcvcEjl1++2GIsKDM4cs6kjBFFVps4iA1G2aZp/xpGP1HiX n8ZKlJQXRzAoczghj+S49xpZXEeTtrTMpt0UdNGZmCABuCTguWXXD3hJLW8sUp2r9Bgj ABt421oXRquRYJWRRBzY40cRJxXuP7HoVPU62pwTELH55MZBwem2t7lTfnZIfEDQ9cwp RWSyj18oyE17L/YCxGsP1LdmtlB5zfwvBrOtukO8tD1CHyiFb3SDs0qiQ4EiH9GynBt5 9eqw== X-Gm-Message-State: AJIora9aOZVIp4n+tAus/iductITMO3wJyXvYpYBrMQSiUX80qiSnAb4 Bcw3xoYlW21g72z9rAy5yD350MbB/1qbDIdZYHSx3w== X-Google-Smtp-Source: AGRyM1uoT5k2AzWm2sUZ0Yc2Jotw9Q640Y0blCoYsXf/yiCPhTmrtfOkD5fG+PcUOVI1lB/0k6sejWFR2KILDr6W1Xk= X-Received: by 2002:a81:3ac5:0:b0:317:8cb0:99b0 with SMTP id h188-20020a813ac5000000b003178cb099b0mr21237745ywa.71.1655798025996; Tue, 21 Jun 2022 00:53:45 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Fangrui Song Date: Tue, 21 Jun 2022 01:53:34 -0600 Message-ID: Subject: Re: [PATCH] Introduce -nolibstdc++ option To: Richard Biener , Alexandre Oliva Cc: GCC Patches , Nathan Sidwell , Joseph Myers Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-23.6 required=5.0 tests=BAYES_00, DKIMWL_WL_MED, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, ENV_AND_HDR_SPF_MATCH, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE, USER_IN_DEF_DKIM_WL, USER_IN_DEF_SPF_WL 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 07:53:48 -0000 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++. > > > > 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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