On Thu, Nov 4, 2021 at 9:03 PM Iain Sandoe via Gcc-patches <gcc-patches@gcc.gnu.org> wrote: > > GCC (currently) has an implementation of pre-compiled-headers, that relies > on being able to launch the compiler executable at the same address each > time. This constraint is not permitted by some system security models. > > The facility is an optimisation; saving the output of parsing a covering > header file (that may include many others) so that the parsing need not be > repeated when the same set of headers is needed in many places in a project. > > The patch series disables the operation of the PCH-related command lines, > but does not cause an error to be emitted. The intent is that build > recipes that expect PCH to work will continue to operate, but the compiler > no longer acts on them and therefore is no longer bound to the requirement > to launch at a fixed address. > > * When invoked to "generate PCH" the compiler will carry out the parsing > as before - producing any diagnostics if relevant and then saving a > stub file (to satisfy build recipe targets). The stub file is marked as > invalid PCH. > > * When an include directive is encountered, the compiler no longer checks > to see if a PCH header is available. > > * The top-level configure option (--disable-host-pch-support) is also > propagated to libstdc++ where it causes the automatic invocation of the > existing --disable-libstdxx-pch. > > tested on x86_64-darwin, aarch64-darwin, and on x86_64, powerpc64le-linux, > OK for master?
I had the impression we have support for PCH file relocation to deal with ASLR at least on some platforms. But it's IMHO nice to have a way to disable PCH and that paves the way to have it disabled by default for a release before we eventually nuke support completely (and then provide a backward-compatible stub implementation). So - OK if there are no complaints from reviewers of their respective area the series touches. Thanks, Richard. > thanks > Iain > > Iain Sandoe (4): > config: Add top-level flag to disable host PCH. > libstdc++: Adjust build of PCH files accounting configured host > support. > libcpp: Honour a configuration without host support for PCH. > c-family, gcc: Allow configuring without support for PCH. > > Makefile.def | 9 ++-- > Makefile.in | 87 +++++++++++++++++++++++++-------------- > configure | 42 +++++++++++++++++++ > configure.ac | 35 ++++++++++++++++ > gcc/c-family/c-pch.c | 23 ++++++++++- > gcc/config.in | 6 +++ > gcc/config/host-darwin.c | 18 ++++++++ > gcc/configure | 29 ++++++++++++- > gcc/configure.ac | 17 ++++++++ > gcc/doc/install.texi | 6 +++ > libcpp/config.in | 3 ++ > libcpp/configure | 24 +++++++++++ > libcpp/configure.ac | 16 +++++++ > libcpp/files.c | 14 +++++++ > libcpp/pch.c | 12 ++++++ > libstdc++-v3/acinclude.m4 | 49 +++++++++++++--------- > libstdc++-v3/configure | 71 +++++++++++++++++++++----------- > libstdc++-v3/configure.ac | 11 ++++- > 18 files changed, 391 insertions(+), 81 deletions(-) > > -- > 2.24.3 (Apple Git-128) >
