Re: [PATCH] Only add -fno-var-tracking-assignments workaround for old GCC versions.

Sedat Dilek
2020-10-14T15:31:54Z

On Mon, Oct 12, 2020 at 9:12 PM Mark Wielaard <mark@klomp.org> wrote:
>
> Hi,
>
> On Mon, 2020-10-12 at 11:59 -0700, Nick Desaulniers wrote:
> > On Sat, Oct 10, 2020 at 3:57 PM Ian Rogers <irogers@google.com>
> > wrote:
> > > On Sat, Oct 10, 2020 at 3:08 PM Mark Wielaard <mark@klomp.org>
> > > wrote:
> > > > -DEBUG_CFLAGS := $(call cc-option, -fno-var-tracking-
> > > > assignments)
> > > > +# Workaround https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61801
> > > > +# for old versions of GCC.
> > > > +DEBUG_CFLAGS := $(call cc-ifversion, -lt, 0500, $(call cc-
> > > > option, -fno-var-tracking-assignments))
> >
> > Should this be wrapped in: `ifdef CONFIG_CC_IS_GCC`/`endif`?
>
> I don't think so. It wasn't before. And call cc-option makes sure to
> only add the flag if the compiler supports it (clang doesn't and it
> also has a much higher version).
>

I am also in favour of `ifdef CONFIG_CC_IS_GCC` to clearly say this is
a GCC bug.

For the comment something like:

# Workaround for GCC version <= 5.0
# GCC Bug: <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61801>

Think of people grepping in the Linux source code for supported or
broken compiler (versions)...
As a reference see ClangBuiltLinux issue #427 "audit use of __GNUC__".
[2] says:
"There's also a ton of __GNUC_MINOR__ checks against unsupported GCC versions."

- Sedat -

[1] https://github.com/ClangBuiltLinux/linux/issues/427
[2] https://github.com/ClangBuiltLinux/linux/issues/427#issuecomment-700935241