From: Richard Sandiford <richard.sandiford@arm.com>
To: Keith Packard via Gcc-patches <gcc-patches@gcc.gnu.org>
Cc: gcc@gcc.gnu.org, Keith Packard <keithp@keithp.com>
Subject: Re: [PATCH 0/3] picolibc: Add picolibc linking help
Date: Fri, 02 Sep 2022 13:36:23 +0100 [thread overview]
Message-ID: <mptwnamar7c.fsf@arm.com> (raw)
In-Reply-To: <20220824180426.820576-1-keithp@keithp.com> (Keith Packard via Gcc-patches's message of "Wed, 24 Aug 2022 11:04:23 -0700")
Keith Packard via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> Picolibc is a C library for embedded systems based on code from newlib
> and avr libc. To connect some system-dependent picolibc functions
> (like stdio) to an underlying platform, the platform may provide an OS
> library.
>
> This OS library must follow the C library in the link command line. In
> current picolibc, that is done by providing an alternate .specs file
> which can rewrite the *lib spec to insert the OS library in the right
> spot.
>
> This patch series adds the ability to specify the OS library on the
> gcc command line when GCC is configured to us picolibc as the default
> C library, and then hooks that up for arm, nds32, riscv and sh targets.
Not really my area, but the approach LGTM FWIW. Main question/points:
- In:
+case "${with_default_libc}" in
+glibc)
+ default_libc=LIBC_GLIBC
+ ;;
should there be a default case that raises an error for unrecognised
libcs? Command-line checking for configure isn't very tight, but we
do raise similar errors for things like invalid --enable-threads values.
- I'm not sure either way about adding LIBC_NEWLIB. On the one hand
it makes sense for completeness, but on the other it's write-only.
Adding it means that --with-default-libc=newlib toolchains have a
different macro configuration from a default toolchain even in cases
where newlib is the default.
On balance I think it would be better to accept
--with-default-libc=newlib but set default_libc to the empty string.
- Should we raise an error for toolchains that don't support the given
C library? It feels like we should, but I realise that could be
difficult to do.
- Very minor, but in lines like:
+#if defined(DEFAULT_LIBC) && defined(LIBC_PICOLIBC) && DEFAULT_LIBC == LIBC_PICOLIBC
is LIBC_PICOLIB ever undefined? It looks like config.gcc provides
an unconditional definition. If it is always defined then:
#if DEFAULT_LIBC == LIBC_PICOLIB
would be clearer.
Thanks,
Richard
>
> Keith Packard (3):
> Allow default libc to be specified to configure
> Add newlib and picolibc as default C library choices
> Add '--oslib=' option when default C library is picolibc
>
> gcc/config.gcc | 56 ++++++++++++++++++++++++++++++++-------
> gcc/config/arm/elf.h | 5 ++++
> gcc/config/nds32/elf.h | 4 +++
> gcc/config/picolibc.opt | 26 ++++++++++++++++++
> gcc/config/riscv/elf.h | 4 +++
> gcc/config/sh/embed-elf.h | 5 ++++
> gcc/configure.ac | 4 +++
> 7 files changed, 95 insertions(+), 9 deletions(-)
> create mode 100644 gcc/config/picolibc.opt
next prev parent reply other threads:[~2022-09-02 12:36 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-24 18:04 Keith Packard
2022-08-24 18:04 ` [PATCH 1/3] picolibc: Allow default libc to be specified to configure Keith Packard
2022-08-24 18:04 ` [PATCH 2/3] picolibc: Add newlib and picolibc as default C library choices Keith Packard
2022-08-24 18:04 ` [PATCH 3/3] picolibc: Add '--oslib=' option when default C library is picolibc Keith Packard
2022-08-24 18:24 ` [PATCH 0/3] picolibc: Add picolibc linking help Andrew Pinski
2022-09-02 12:36 ` Richard Sandiford [this message]
2022-09-03 6:02 ` Keith Packard
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