Jakub Jelinek 于2023年12月18日周一 16:10写道：
>
> On Mon, Dec 18, 2023 at 11:44:21AM +0800, YunQiang Su wrote:
> > The function `reconcat` cannot append string(s) to NULL,
> > as the concat process will stop at the first NULL.
> >
> > Let's initialize `ret` with `concat (" ", NULL)`, then
> > it can be used by reconcat.
> >
> > gcc/
> >
> > PR target/112759
> > * config/mips/driver-native.cc (host_detect_local_cpu):
> > initialize ret with concat, so that it can be used by
> > reconcat later.
> > ---
> > gcc/config/mips/driver-native.cc | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/gcc/config/mips/driver-native.cc
> > b/gcc/config/mips/driver-native.cc
> > index afc276f5278..471d1925eff 100644
> > --- a/gcc/config/mips/driver-native.cc
> > +++ b/gcc/config/mips/driver-native.cc
> > @@ -44,7 +44,7 @@ const char *
> > host_detect_local_cpu (int argc, const char **argv)
> > {
> >const char *cpu = NULL;
> > - char *ret = NULL;
> > + char *ret = concat(" ", NULL);
> >char buf[128];
> >FILE *f;
> >bool arch;
> > --
> > 2.39.2
>
> The formatting is wrong (no space after concat), but more importantly,
I will fix the format.
> I don't think you want to return " " rather than NULL if there isn't
> anything known and it is unnecessary to prefix everything with a space
> when
> gnu-user.h: " %{march=native:% gnu-user.h: " %{mtune=native:% space is already present. Given the simple thing the function does,
> I think much better would be to avoid any reconcat calls and just do one
> concat, i.e.
> --- gcc/config/mips/driver-native.cc2023-01-02 09:32:58.422764590 +0100
> +++ gcc/config/mips/driver-native.cc2023-12-18 09:08:39.547609739 +0100
> @@ -44,6 +44,7 @@ const char *
> host_detect_local_cpu (int argc, const char **argv)
> {
>const char *cpu = NULL;
> + const char *nan2008 = "";
>char *ret = NULL;
>char buf[128];
>FILE *f;
> @@ -90,7 +91,7 @@ host_detect_local_cpu (int argc, const c
>
> fallback_cpu:
> #if defined (__mips_nan2008)
> - ret = reconcat (ret, " -mnan=2008 ", NULL);
> + nan2008 = "-mnan=2008 ";
> #endif
>
> #ifdef HAVE_GETAUXVAL
> @@ -104,7 +105,9 @@ fallback_cpu:
> #endif
>
>if (cpu)
> -ret = reconcat (ret, ret, "-m", argv[0], "=", cpu, NULL);
> +ret = concat (nan2008, "-m", argv[0], "=", cpu, NULL);
> + else if (nan2008)
> +ret = concat (nan2008, NULL);
>
>return ret;
> }
>
>
> Or, if you really want to use reconcat, drop that space from
> before -mnan=2008 and use
> ret = reconcat (ret, ret ? ret : "", "-m", argv[0], "=", cpu, NULL);
>
Good idea.
Maybe that we can use
ret = reconcat (ret, "-m", argv[0], "=", cpu, ret, NULL);
Then won't worry about ret is NULL here.
One reason I want to use reconcat is that I try to avoid something
wrong in future,
if somebody else add some new detect conditions.
With reconcat, the person will need only copy/paste ;)
It will reduce the possibility for doing something wrong in future.
And let's add a comment here.
> Jakub
>
