[Bug bootstrap/87858] Building old multilib bootstrap GCC: stage1 32-bit libstdc++ fails to build after building 64-bit libstdc++

["mkrupcale at matthewkrupcale dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87858

--- Comment #6 from Matthew Krupcale <mkrupcale at matthewkrupcale dot com> ---
(In reply to Andrew Pinski from comment #5)
> Best way to support this really is to build a 4.8 cross compiler and then
> build a canandian cross GCC 4.8 and then bootstrap a 4.8.x using that newly
> build canandian cross compiler.

I'm not sure I follow exactly because I wasn't trying to build a cross
compiler, although I suppose once you have a GCC 4.8 compiler built (cross or
not), you wouldn't have a problem building 4.8.x with it in theory. But the
problem is building that initial GCC 4.8 (cross or not) with the newer GCC
version.

> New enough GCC uses -static-libstdc++ and that avoids the shared library
> problem mentioned here.

This won't help during stage1 of the bootstrap build if you don't have the
static libstdc++ library installed on the build host. Once the static libstdc++
library is built, this problem won't happen during the later stages. For
stage1, however, GCC will currently attempt to use the build host libstdc++ and
its newer symbols for building host executables. When the old libstdc++ is
built then--and in the absence of a static libstdc++ on the build host--the
host executables will fail to load due to the old libstdc++ being on
LD_LIBRARY_PATH and lacking the newer symbols required by the host executables.

Note that as far as I'm aware, this issue still exists in modern versions of
GCC and is not exclusive to building only GCC 4.8. As shown by comment 3 and
comment 4, this problem is demonstrable by building GCC v8.2.1 or v10 with GCC
11 and possibly other versions. I was also able to confirm in comment 3 that my
patch for GCC 8.2 did resolve the issue when building with GCC 11.