On Sat, 2021-06-19 at 16:12 +0900, Kazuyoshi Furutaka via Gcc-help wrote: > Dear Xi Ruoyao, thanks for your suggestion. > > From: Xi Ruoyao <xry111@xxxxxxxxxxxxxxxx> > Subject: Re: Problem building older versions of gcc > Date: Sat, 19 Jun 2021 12:26:38 +0800 > > > On Fedora 33 there should be the same problem. But Fedora 33 may have > > a > > same libstdc++.so.6 version with gcc-10.x, so the newly built library > > is > > compatible completely with the system one and no issue is observed. > > In the Fedora-33 testing system on QEMU/KVM (with gcc-10.3.1 installed), > I've also tried the builds of gcc-9.4.0 and gcc-8.5.0, and the builds > ended > successfully. (by the way, the versions of libstdc++ are the same, > 6.0.29, > on both testing Fedora-33 and Fedora-34 systems) > > > From: Xi Ruoyao <xry111@xxxxxxxxxxxxxxxx> > Subject: Re: Problem building older versions of gcc > Date: Sat, 19 Jun 2021 12:29:19 +0800 > > > On Sat, 2021-06-19 at 12:26 +0800, Xi Ruoyao via Gcc-help wrote: > > > > > Anyway, GCC executables should not link to libstdc++.so.6. Is > > > libstdc++.a installed on your Fedora 34? Note that Fedora > > > maintainers > > > may split it into a seperate package. > > > > A quick search confirmed my guess: > > > > https://fedora.pkgs.org/34/fedora-x86_64/libstdc++-static-11.0.1-0.3.fc34.x86_64.rpm.html > > I'm sorry but what are your points? > > Indeed, as I mentioned in the previous post, in Fedora there's > a separate package for static libstdc++ library, and as I wrote, > only after installing it, the build with simple (--prefix only) > configuration succeeded on a Fedora-34 system. > > And, the cc1plus installed in Fedora-34 does not depend on > the system's libstdc++: > > > [furutaka@peart-furu-or-jp gcc]$ rpm -ql gcc-c++|grep cc1plus > > /usr/libexec/gcc/x86_64-redhat-linux/11/cc1plus > > [furutaka@peart-furu-or-jp gcc]$ ldd /usr/libexec/gcc/x86_64-redhat- > > linux/11/cc1plus > > linux-vdso.so.1 (0x00007ffd00acc000) > > libdl.so.2 => /lib64/libdl.so.2 (0x0000153c91528000) > > libmpc.so.3 => /lib64/libmpc.so.3 (0x0000153c91508000) > > libmpfr.so.6 => /lib64/libmpfr.so.6 (0x0000153c91458000) > > libgmp.so.10 => /lib64/libgmp.so.10 (0x0000153c913b0000) > > libz.so.1 => /lib64/libz.so.1 (0x0000153c91390000) > > libzstd.so.1 => /lib64/libzstd.so.1 (0x0000153c91298000) > > libm.so.6 => /lib64/libm.so.6 (0x0000153c91150000) > > libc.so.6 => /lib64/libc.so.6 (0x0000153c90f80000) > > /lib64/ld-linux-x86-64.so.2 (0x0000153c91568000) > > libpthread.so.0 => /lib64/libpthread.so.0 (0x0000153c90f58000) > > On the other hand, the stage-1 cc1plus is built in advance > to libstdc++.so, and therefore I think it's inevitable that > the stage-1 cc1plus depends on the system's libstdc++.so > (or else the stage-1 cc1plus should be statically linked). > > So... > > > I think gcc building system is setting LD_LIBRARY_PATH somewhere. So > > during building process the newly built libstdc++.so.6 is found, > > instead > > of the system library. > I think that the newly built stage-1 cc1plus CAN NOT use > for itself the new libstdc++.so.6 because it does NOT exist. >From your log, it can be seen it's already built: > /home/furutaka/work/gcc/gcc-10.3.0-bld/./gcc/cc1plus: > /home/furutaka/work/gcc/gcc-10.3.0-bld/x86_64-pc-linux-gnu/libstdc++- v3/src/.libs/libstdc++.so.6: > version `GLIBCXX_3.4.29' not found (required by > /home/furutaka/work/gcc/gcc-10.3.0-bld/./gcc/cc1plus) x86_64-pc-linux-gnu/libstdc++-v3/src/.libs/libstdc++.so.6 is there. > By the way, LD_LIbRARY_PATH is not defined on both F33 & F34 systems. It's not F33 or F34 sets LD_LIBRARY_PATH, it's GCC building system setting it. > So, I'm still wondering the cause of the differences between > the two systems. Fedora 33 is using GCC 10, which matches the GCC version you are building. When libstdc++.a is not installed, stage 1 cc1plus etc. links to system libstdc++.so. GCC building system (automatically) sets LD_LIBRARY_PATH to contain newly built runtime libraries. So a newly built libstdc++.so is found anyway. On Fedora 33 system the libstdc++.so built in stage 1 is compatible with system one. On Fedora 34 it's not. -- Xi Ruoyao <xry111@xxxxxxxxxxxxxxxx> School of Aerospace Science and Technology, Xidian University
