Picolibc is a fork of newlib designed and tested on embedded systems. It
offers a smaller memory footprint (both ROM and RAM), and native TLS
support, which uses the Zephyr TLS support.
By default, the full printf version is included in the executable, which
includes exact floating point and long long input and output. A
configuration option has been added to switch to the integer-only
version (which also omits long long support).
Here are some size comparisons using qemu-cortex-m3 and this application
(parameters passed to printf to avoid GCC optimizing it into puts):
void main(void)
{
printf("Hello World! %s %d\n", CONFIG_BOARD, 12);
}
FLASH SRAM
minimal 8696 3952
picolibc int 7600 3960
picolibc float 12304 3960
newlib-nano int 11696 4128
newlib-nano float 30516 4496
newlib 34800 6112
---
v2:
Include picolibc-tls.ld
v3:
Document usage in guides/c_library.rst and
getting_started/toolchain_other_x_compilers.rst
v4:
Lost the lib/libc/picolibc directory somehow!
v5:
Add PICOLIBC_ALIGNED_HEAP_SIZE configuration option.
Delete PICOLIBC_SEMIHOST option support code
v6:
Don't allocate static RAM for TLS values; TLS
values only need to be allocated for each thread.
v7:
Use arm coprocessor for TLS pointer storage where supported for
compatibility with the -mtp=cp15 compiler option (or when the
target cpu type selects this option)
Add a bunch of tests
Round TLS segment up to stack alignment so that overall stack
remains correctly aligned
Add aarch64 support
Rebase to upstream head
v8:
Share NEWLIB, NEWLIB_NANO and PICOLIBC library configuration
variables in a single LIBC_PARTITIONS variable instead of
having separate PICOLIBC_PART and NEWLIB_PART variables.
v9:
Update docs to reference pending sdk-ng support for picolibc
v10:
Support memory protection by creating a partition for
picolibc shared data and any pre-defined picolibc heap.
v11:
Fix formatting in arch/arm/core/aarch64/switch.S
v12:
Remove TLS support from this patch now that TLS is upstream
Require THREAD_LOCAL_STORAGE when using PICOLIBC for architectures
that support it.
v13:
Merge errno changes as they're only needed for picolibc.
Adapt cmake changes suggested by Torsten Tejlmand Rasmussen
v14:
Update to picolibc 1.7 and newer (new stdin/stdout/stderr ABI)
v15:
Respond to comments from dcpleung:
* switch kernel/errno to use CONFIG_LIBC_ERRNO instead of
CONFIG_PICOLIBC
* Add comment to test/lib/sprintf as to why the %n test
was disabled for picolibc.
v16:
Switch picolibc to a module built with Zephyr. This eliminates
toolchain dependencies and allows compiler settings for Zephyr
to also be applied to picolibc.
v17:
Provide Zephyr-specific 'abort' implementation.
Support systems with MMU
v18:
Allow use of toolchain picolibc version.
v19:
Use zephyr/ for zephyr headers
v20:
Add locking
Use explicit commit for picolibc module
v21:
Create PICOLIBC_SUPPORTED config param. Set on arc, arm, arm64,
mips and riscv architectures.
Signed-off-by: Keith Packard <keithp@keithp.com>
Keith Packard