From: "H.J. Lu" <hjl.tools@gmail.com>
To: Christian Biesinger <cbiesinger@google.com>
Cc: Joseph Myers <joseph@codesourcery.com>,
Matthias Klose <doko@ubuntu.com>,
GCC Patches <gcc-patches@gcc.gnu.org>,
Binutils <binutils@sourceware.org>,
GDB <gdb-patches@sourceware.org>
Subject: Re: V3 [PATCH 5/5] gnulib: Support variables from the top level Makefile
Date: Tue, 5 Jan 2021 06:06:44 -0800 [thread overview]
Message-ID: <CAMe9rOoSp9LOk8GAeezparWk_jBJO2YKispw_3dK8=pvtwPX3A@mail.gmail.com> (raw)
In-Reply-To: <CAPTJ0XGAPAn=QQ-d8Vm1mp0_Szd8+xn0eob9Hni6_+Ysqifbqg@mail.gmail.com>
On Tue, Jan 5, 2021 at 5:27 AM Christian Biesinger
<cbiesinger@google.com> wrote:
>
> On Fri, Jan 1, 2021 at 1:07 AM H.J. Lu via Gdb-patches
> <gdb-patches@sourceware.org> wrote:
> >
> > On Thu, Dec 31, 2020 at 3:50 PM Joseph Myers <joseph@codesourcery.com> wrote:
> > >
> > > On Sat, 19 Dec 2020, H.J. Lu via Gcc-patches wrote:
> > >
> > > > Work around what appears to be a GNU make bug handling MAKEFLAGS
> > > > values defined in terms of make variables, as is the case for CC and
> > > > friends when we are called from the top level Makefile.
> > >
> > > This description, and the comment in Makefile.am repeating it, is rather
> > > unhelpful as it provides no way for a reader to know what the supposed bug
> > > is. Reviewers need to be able to work out whether the proposed workaround
> > > is correct or the right approach for working around the bug. Maintainers
> > > in future need to be able to tell what the bug is. So the comment needs
> > > to explain what the bug is and give a reference to a report for the bug in
> > > the GNU make bug tracker, so that subsequent maintainers can look at that
> > > bug to tell if the workaround is still needed at all.
> > >
> >
> > I just copied the same workaround from other directories in GCC.
>
> But could you explain under which circumstances the bug happens?
>
To rebuild a subdirectory with different CFLAGS/CXXFLAGS without
regenerating new Makefiles, like bootstrapping GCC and doing PGO
build in binutils/GDB, we pass new CFLAGS/CXXFLAGS from
toplevel Makefile to the subdirectory. Without this workaround, the old
CFLAGS/CXXFLAGS are used in the subdirectory. The same workaround
is used in subdirectories for bootstrapping GCC. My patch extends
it to GDB for PGO build.
--
H.J.
next prev parent reply other threads:[~2021-01-05 14:07 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-19 18:10 V3 [PATCH 0/5] Support the PGO build for binutils+gdb H.J. Lu
2020-12-19 18:10 ` V3 [PATCH 1/5] GCC: Pass --plugin to AR and RANLIB H.J. Lu
2020-12-19 18:10 ` V3 [PATCH 2/5] Binutils: " H.J. Lu
2020-12-19 18:10 ` V3 [PATCH 3/5] Support the PGO build for binutils+gdb H.J. Lu
2021-02-28 7:01 ` Mike Frysinger
2021-02-28 12:44 ` [PATCH] Add missing changes to Makefile.tpl H.J. Lu
2020-12-19 18:10 ` V3 [PATCH 4/5] Set TESTS to gdb.dwarf2/*.exp for PGO build training H.J. Lu
2020-12-19 18:10 ` V3 [PATCH 5/5] gnulib: Support variables from the top level Makefile H.J. Lu
2020-12-31 23:50 ` Joseph Myers
2021-01-01 0:06 ` H.J. Lu
2021-01-05 13:26 ` Christian Biesinger
2021-01-05 14:06 ` H.J. Lu [this message]
2021-01-02 19:22 ` V3 [PATCH 0/5] Support the PGO build for binutils+gdb Segher Boessenkool
2021-01-02 19:46 ` H.J. Lu
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