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Picolibc cplusplus #620

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Merged
merged 2 commits into from
Feb 20, 2023
Merged

Picolibc cplusplus #620

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0d764d5
cmake: set TOOLCHAIN_HAS_PICOLIBC
tejlmand Jan 13, 2023
413cbfb
kconfig: define PICOLIBC_SUPPORTED to `y`
tejlmand Jan 13, 2023
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6 changes: 6 additions & 0 deletions cmake/zephyr/Kconfig
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Expand Up @@ -7,3 +7,9 @@ config TOOLCHAIN_ZEPHYR_0_15
config TOOLCHAIN_ZEPHYR_SUPPORTS_THREAD_LOCAL_STORAGE
def_bool y
select TOOLCHAIN_SUPPORTS_THREAD_LOCAL_STORAGE

config PICOLIBC_SUPPORTED
def_bool y
depends on "$(ZEPHYR_TOOLCHAIN_VARIANT)" = "zephyr"
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What effect would this have on other toolchains? For instance, you can add picolibc support to the arm embedded toolkit by downloading the picolibc overlay, you can build native a crosstool-ng toolchain which can have picolibc support included, or you could be using the native Debian arm-none-eabi toolchain, which has picolibc support.

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What effect would this have on other toolchains?

None.
This only sets the setting to y when Zephyr SDK is used.
When another toolchain is used, then the setting inside the Zephyr repo is used.

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oh. How does this detect whether the user is building the picolibc module? Because you could be using the zephyr toolchain but not using the picolibc bits it provides, and that wouldn't work for C++.

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This doesn't allow Zephyr to restrict picolibc usage for boards that don't work, even if picolibc works for the target architecture (like qemu_x86_tiny). Perhaps this should use a new variable, TOOLCHAIN_PICOLIBC_SUPPORTED, and that variable could be used in the computation of PICOLIBC_SUPPORTED?

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This doesn't allow Zephyr to restrict picolibc usage for boards that don't work, even if picolibc works for the target architecture (like qemu_x86_tiny).

Correct, so if we do have such boards then we need to consider how to handle them.

What is the reason that a given board would impact the use of picolibc ?
Especially as from your description, the architecture itself is supported.
(and is it really the board, and not the SoC which are restricting picolibc ?)

Do you have some concrete examples ?

Probably this is something which should be handle directly at the board, and the board Kconfig in fact has a possibility to default the TOOLCHAIN_PICOLIBC_SUPPORTED to n if this is needed.

help
Zephyr SDK >=0.16 always supports Picolibc for C and C++ development.
1 change: 1 addition & 0 deletions cmake/zephyr/generic.cmake
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Expand Up @@ -30,3 +30,4 @@ endif()
set(CROSS_COMPILE ${one_toolchain_root}/${CROSS_COMPILE_TARGET}/bin/${CROSS_COMPILE_TARGET}-)
set(SYSROOT_DIR ${one_toolchain_root}/${SYSROOT_TARGET}/${SYSROOT_TARGET})
set(TOOLCHAIN_HAS_NEWLIB ON CACHE BOOL "True if toolchain supports newlib")
set(TOOLCHAIN_HAS_PICOLIBC ON CACHE BOOL "True if toolchain supports picolibc")