libstdc++ is supported with Picolibc only when the toolchain version of
Picolibc is use -- libstdc++ must be built using a specific Picolibc build
and libstdc++ is included with the toolchain.
Ideally, we'd allow the use of the Picolibc module whenever we weren't
using the GNU libstdc++, including when using the minimal libc++. However,
the obvious dependency settings create a loop:
config PICOLIBC
depends on PICOLIBC_SUPPORTED
config PICOLIBC_SUPPORTED
depends on !(GLIBCXX_LIBCPP && "$(ZEPHYR_TOOCHAIN_VARIANT" = "zephyr")
config GLIBCXX_LIBCPP
depends on NEWLIB_LIBC || PICOLIBC
To break this loop, we replace GLIBCXX_LIBCPP in the second block with
CPP:
config PICOLIBC_SUPPORTED
depends on !(CPP && "$(ZEPHYR_TOOCHAIN_VARIANT" = "zephyr")
This means that picolibc cannot be used with any C++ apps when using the
Zephyr SDK, even when not using the GNU libstdc++. However, Zephyr SDK 0.16
will come with an additional Kconfig file that includes:
config PICOLIBC_SUPPORTED
def_bool y
depends on "$(ZEPHYR_TOOLCHAIN_VARIANT)" = "zephyr"
This will override the Kconfig bits included in Zephyr and allow use of the
Picolibc module with C++ code, including using the minimal libc++ bits.
Signed-off-by: Keith Packard <keithp@keithp.com>
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