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
