Dear Xi Ruoyao, thanks again. From: Xi Ruoyao <xry111@xxxxxxxxxxxxxxxx> Subject: Re: Problem building older versions of gcc Date: Sat, 19 Jun 2021 15:28:16 +0800 >> 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: I said that libstdc++.so.6 was NOT THERE WHEN cc1plus WAS BUILT, and the newly built cc1plus should depend on the system's. >> /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. You pointed at the error occured, where the newly built cc1plus was USED, and the newly built libstdc++.so.6 was used to build "-o x86_64-pc-linux-gnu/bits/stdc++.h.gch/O2g.gch" or something like that. >> 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. What about the success of gcc-9.4.0 and gcc-8.5.0 builds? > 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. It may be so for the gcc-10.3.0 build, but for gcc-8.5.0 build, > [furutaka@localhost gcc-8.5.0-bld]$ strings /lib64/libstdc++.so.6 | grep "^GLIBCXX_3.4.2" | sort | uniq > GLIBCXX_3.4.2 > GLIBCXX_3.4.20 > GLIBCXX_3.4.21 > GLIBCXX_3.4.22 > GLIBCXX_3.4.23 > GLIBCXX_3.4.24 > GLIBCXX_3.4.25 > GLIBCXX_3.4.26 > GLIBCXX_3.4.27 > GLIBCXX_3.4.28 > [furutaka@localhost gcc-8.5.0-bld]$ strings ./stage1-x86_64-pc-linux-gnu/libstdc++-v3/src/.libs/libstdc++.so.6 | grep "^GLIBCXX_3.4.2" | sort | uniq > GLIBCXX_3.4.2 > GLIBCXX_3.4.20 > GLIBCXX_3.4.21 > GLIBCXX_3.4.22 > GLIBCXX_3.4.23 > GLIBCXX_3.4.24 > GLIBCXX_3.4.25 that is, I think the newly built library do not have at least a few symbols that the sytem library have. Can we think they are still compatible? Could you be kind enought to point me to some good web pages or books in/on which GCC's 3-stage building processes and how the linker works? Thanks, Kazuyoshi -- Kazuyoshi Furutaka furutaka@xxxxxxxxxxxxxxxx
