70f44ec6fe
Docgen updates the docs when the config options are changed. This update has been waiting since https://github.com/llvm/llvm-project/pull/143187.
65 lines
4.8 KiB
ReStructuredText
65 lines
4.8 KiB
ReStructuredText
.. _configure:
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..
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Do not edit this file directly. CMake will auto generate it.
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If the changes are intended, add this file to your commit.
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==========================
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Configure Options
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==========================
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Below is the full set of options one can use to configure the libc build.
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An option can be given an explicit value on the CMake command line using
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the following syntax:
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.. code-block:: sh
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$> cmake <other build options> -D<libc config option name>=<option value> <more options>
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For example:
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.. code-block:: sh
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$> cmake <other build options> -DLIBC_CONF_PRINTF_DISABLE_FLOAT=ON <more options>
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See the main ``config/config.json``, and the platform and architecture specific
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overrides in ``config/<platform>/config.json`` and ``config/<platform>/<arch>/config.json,``
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to learn about the defaults for your platform and target.
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* **"codegen" options**
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- ``LIBC_CONF_ENABLE_STRONG_STACK_PROTECTOR``: Enable -fstack-protector-strong to defend against stack smashing attack.
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- ``LIBC_CONF_KEEP_FRAME_POINTER``: Keep frame pointer in functions for better debugging experience.
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* **"errno" options**
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- ``LIBC_CONF_ERRNO_MODE``: The implementation used for errno, acceptable values are LIBC_ERRNO_MODE_DEFAULT, LIBC_ERRNO_MODE_UNDEFINED, LIBC_ERRNO_MODE_THREAD_LOCAL, LIBC_ERRNO_MODE_SHARED, LIBC_ERRNO_MODE_EXTERNAL, LIBC_ERRNO_MODE_SYSTEM, and LIBC_ERRNO_MODE_SYSTEM_INLINE.
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* **"general" options**
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- ``LIBC_ADD_NULL_CHECKS``: Add nullptr checks in the library's implementations to some functions for which passing nullptr is undefined behavior.
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* **"math" options**
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- ``LIBC_CONF_FREXP_INF_NAN_EXPONENT``: The value written back to the second parameter when calling frexp/frexpf/frexpl` with `+/-Inf`/`NaN` is unspecified. Configure an explicit exp value for Inf/NaN inputs.
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- ``LIBC_CONF_MATH_OPTIMIZATIONS``: Configures optimizations for math functions. Values accepted are LIBC_MATH_SKIP_ACCURATE_PASS, LIBC_MATH_SMALL_TABLES, LIBC_MATH_NO_ERRNO, LIBC_MATH_NO_EXCEPT, and LIBC_MATH_FAST.
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* **"printf" options**
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- ``LIBC_CONF_PRINTF_DISABLE_FIXED_POINT``: Disable printing fixed point values in printf and friends.
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- ``LIBC_CONF_PRINTF_DISABLE_FLOAT``: Disable printing floating point values in printf and friends.
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- ``LIBC_CONF_PRINTF_DISABLE_INDEX_MODE``: Disable index mode in the printf format string.
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- ``LIBC_CONF_PRINTF_DISABLE_STRERROR``: Disable handling of %m to print strerror in printf and friends.
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- ``LIBC_CONF_PRINTF_DISABLE_WRITE_INT``: Disable handling of %n in printf format string.
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- ``LIBC_CONF_PRINTF_FLOAT_TO_STR_NO_SPECIALIZE_LD``: Use the same mode for double and long double in printf.
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- ``LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_DYADIC_FLOAT``: Use dyadic float for faster and smaller but less accurate printf doubles.
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- ``LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_FLOAT320``: Use an alternative printf float implementation based on 320-bit floats
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- ``LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_MEGA_LONG_DOUBLE_TABLE``: Use large table for better printf long double performance.
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- ``LIBC_CONF_PRINTF_RUNTIME_DISPATCH``: Use dynamic dispatch for the output mechanism to reduce code size.
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* **"pthread" options**
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- ``LIBC_CONF_RAW_MUTEX_DEFAULT_SPIN_COUNT``: Default number of spins before blocking if a mutex is in contention (default to 100).
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- ``LIBC_CONF_RWLOCK_DEFAULT_SPIN_COUNT``: Default number of spins before blocking if a rwlock is in contention (default to 100).
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- ``LIBC_CONF_TIMEOUT_ENSURE_MONOTONICITY``: Automatically adjust timeout to CLOCK_MONOTONIC (default to true). POSIX API may require CLOCK_REALTIME, which can be unstable and leading to unexpected behavior. This option will convert the real-time timestamp to monotonic timestamp relative to the time of call.
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* **"qsort" options**
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- ``LIBC_CONF_QSORT_IMPL``: Configures sorting algorithm for qsort and qsort_r. Values accepted are LIBC_QSORT_QUICK_SORT, LIBC_QSORT_HEAP_SORT.
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* **"scanf" options**
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- ``LIBC_CONF_SCANF_DISABLE_FLOAT``: Disable parsing floating point values in scanf and friends.
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- ``LIBC_CONF_SCANF_DISABLE_INDEX_MODE``: Disable index mode in the scanf format string.
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* **"setjmp" options**
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- ``LIBC_CONF_SETJMP_AARCH64_RESTORE_PLATFORM_REGISTER``: Make setjmp save the value of x18, and longjmp restore it. The AArch64 ABI delegates this register to platform ABIs, which can choose whether to make it caller-saved.
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* **"string" options**
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- ``LIBC_CONF_MEMSET_X86_USE_SOFTWARE_PREFETCHING``: Inserts prefetch for write instructions (PREFETCHW) for memset on x86 to recover performance when hardware prefetcher is disabled.
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- ``LIBC_CONF_STRING_UNSAFE_WIDE_READ``: Read more than a byte at a time to perform byte-string operations like strlen.
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* **"time" options**
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- ``LIBC_CONF_TIME_64BIT``: Force the size of time_t to 64 bits, even on platforms where compatibility considerations would otherwise make it 32-bit.
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