libc/config/config.json

{
  "errno": {
    "LIBC_CONF_ERRNO_MODE": {
      "value": "LIBC_ERRNO_MODE_DEFAULT",
      "doc": "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, and LIBC_ERRNO_MODE_SYSTEM_INLINE."
    }
  },
  "threads": {
    "LIBC_CONF_THREAD_MODE": {
      "value": "LIBC_THREAD_MODE_PLATFORM",
      "doc": "The implementation used for Mutex, acceptable values are LIBC_THREAD_MODE_PLATFORM, LIBC_THREAD_MODE_SINGLE, and LIBC_THREAD_MODE_EXTERNAL."
    }
  },
  "printf": {
    "LIBC_CONF_PRINTF_DISABLE_FLOAT": {
      "value": false,
      "doc": "Disable printing floating point values in printf and friends."
    },
    "LIBC_CONF_PRINTF_DISABLE_INDEX_MODE": {
      "value": false,
      "doc": "Disable index mode in the printf format string."
    },
    "LIBC_CONF_PRINTF_DISABLE_WRITE_INT": {
      "value": false,
      "doc": "Disable handling of %n in printf format string."
    },
    "LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_MEGA_LONG_DOUBLE_TABLE": {
      "value": false,
      "doc": "Use large table for better printf long double performance."
    },
    "LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_DYADIC_FLOAT": {
      "value": false,
      "doc": "Use dyadic float for faster and smaller but less accurate printf doubles."
    },
    "LIBC_CONF_PRINTF_FLOAT_TO_STR_NO_SPECIALIZE_LD": {
      "value": false,
      "doc": "Use the same mode for double and long double in printf."
    },
    "LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_FLOAT320": {
      "value": false,
      "doc": "Use an alternative printf float implementation based on 320-bit floats"
    },
    "LIBC_CONF_PRINTF_DISABLE_FIXED_POINT": {
      "value": false,
      "doc": "Disable printing fixed point values in printf and friends."
    },
    "LIBC_CONF_PRINTF_DISABLE_STRERROR": {
      "value": false,
      "doc": "Disable handling of %m to print strerror in printf and friends."
    },
    "LIBC_CONF_PRINTF_RUNTIME_DISPATCH": {
      "value": true,
      "doc": "Use dynamic dispatch for the output mechanism to reduce code size."
    },
    "LIBC_CONF_PRINTF_DISABLE_WIDE": {
      "value": false,
      "doc": "Disable handling wide characters for printf and friends."
    },
    "LIBC_COPT_PRINTF_DISABLE_BITINT": {
      "value": false,
      "doc": "Disable bitint length modifiers to reduce code size. Specifically the wNUM and wfNUM modifiers."
    },
    "LIBC_CONF_PRINTF_MODULAR": {
      "value": false,
      "doc": "Split printf implementation into modules that can be lazily linked in."
    }
  },
  "scanf": {
    "LIBC_CONF_SCANF_DISABLE_FLOAT": {
      "value": false,
      "doc": "Disable parsing floating point values in scanf and friends."
    },
    "LIBC_CONF_SCANF_DISABLE_INDEX_MODE": {
      "value": false,
      "doc": "Disable index mode in the scanf format string."
    },
    "LIBC_CONF_SCANF_PROVIDE_ISOC99_ALIASES": {
      "value": false,
      "doc": "Add __isoc99_* aliases for scanf's functions."
    }
  },
  "str_to_float": {
    "LIBC_CONF_STRTOFLOAT_DISABLE_EISEL_LEMIRE": {
      "value": false,
      "doc": "Disable Eisel-Lemire algorithm for string to float conversion."
    },
    "LIBC_CONF_STRTOFLOAT_DISABLE_SIMPLE_DECIMAL_CONVERSION": {
      "value": false,
      "doc": "Disable simple decimal conversion for string to float conversion."
    },
    "LIBC_CONF_STRTOFLOAT_DISABLE_CLINGER_FAST_PATH": {
      "value": false,
      "doc": "Disable Clinger's fast path for string to float conversion."
    }
  },
  "string": {
    "LIBC_CONF_STRING_LENGTH_IMPL": {
      "value": "element",
      "doc": "Selects the implementation for string-length: 'element', 'word', 'clang_vector', or 'arch_vector'."
    },
    "LIBC_CONF_FIND_FIRST_CHARACTER_IMPL": {
      "value": "element",
      "doc": "Selects the implementation for find-first-character-related functions: 'element', 'word', 'clang_vector', or 'arch_vector'."
    },
    "LIBC_CONF_MEMSET_X86_USE_SOFTWARE_PREFETCHING": {
      "value": false,
      "doc": "Inserts prefetch for write instructions (PREFETCHW) for memset on x86 to recover performance when hardware prefetcher is disabled."
    },
    "LIBC_CONF_MEMCPY_X86_USE_NTA_STORES": {
      "value": true,
      "doc": "Use Non-temporal stores in memcpy on x86 to improve performance of large copies."
    },
    "LIBC_CONF_USE_MEM_BUILTINS": {
      "value": false,
      "doc": "Use builtins for memory utility functions."
    }
  },
  "ctype": {
    "LIBC_CONF_CTYPE_SMALLER_ASCII": {
      "value": false,
      "doc": "Shrinks b36_char_to_int by assuming the character encoding is ASCII."
    }
  },
  "codegen": {
    "LIBC_CONF_KEEP_FRAME_POINTER": {
      "value": true,
      "doc": "Keep frame pointer in functions for better debugging experience."
    },
    "LIBC_CONF_ENABLE_STRONG_STACK_PROTECTOR": {
      "value": true,
      "doc": "Enable -fstack-protector-strong to defend against stack smashing attack."
    }
  },
  "pthread": {
    "LIBC_CONF_TIMEOUT_ENSURE_MONOTONICITY": {
      "value": true,
      "doc": "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."
    },
    "LIBC_CONF_RAW_MUTEX_DEFAULT_SPIN_COUNT": {
      "value": 100,
      "doc": "Default number of spins before blocking if a mutex is in contention (default to 100)."
    },
    "LIBC_CONF_RWLOCK_DEFAULT_SPIN_COUNT": {
      "value": 100,
      "doc": "Default number of spins before blocking if a rwlock is in contention (default to 100)."
    }
  },
  "math": {
    "LIBC_CONF_MATH_OPTIMIZATIONS": {
      "value": 0,
      "doc": "Configure optimizations for math functions. Values accepted are LIBC_MATH_SKIP_ACCURATE_PASS, LIBC_MATH_SMALL_TABLES, LIBC_MATH_NO_ERRNO, LIBC_MATH_NO_EXCEPT, LIBC_MATH_FAST, LIBC_MATH_INTERMEDIATE_COMP_IN_FLOAT, and LIBC_MATH_ASSUME_ROUND_NEAREST_ONLY."
    },
    "LIBC_CONF_FREXP_INF_NAN_EXPONENT": {
      "value": "",
      "doc": "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."
    },
    "LIBC_CONF_MATH_USE_SYSTEM_FENV": {
      "value": false,
      "doc": "Use C standard fenv.h calls from the system libc instead our internal fenv implementations."
    }
  },
  "qsort": {
    "LIBC_CONF_QSORT_IMPL": {
      "value": "LIBC_QSORT_QUICK_SORT",
      "doc": "Configures sorting algorithm for qsort and qsort_r. Values accepted are LIBC_QSORT_QUICK_SORT, LIBC_QSORT_HEAP_SORT."
    }
  },
  "setjmp": {
    "LIBC_CONF_SETJMP_AARCH64_RESTORE_PLATFORM_REGISTER": {
      "value": true,
      "doc": "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."
    }
  },
  "general": {
    "LIBC_ADD_NULL_CHECKS": {
      "value": true,
      "doc": "Add nullptr checks in the library's implementations to some functions for which passing nullptr is undefined behavior."
    }
  },
  "wctype": {
    "LIBC_CONF_WCTYPE_MODE": {
      "value": "LIBC_WCTYPE_MODE_ASCII",
      "doc": "The implementation used for wctype, acceptable values are LIBC_WCTYPE_MODE_ASCII and LIBC_WCTYPE_MODE_UTF8."
    }
  },
  "fenv": {
    "LIBC_CONF_TRAP_ON_RAISE_FP_EXCEPT": {
      "value": false,
      "doc": "Trap with SIGFPE when feraiseexcept is called with unmasked floating point exceptions, similar to glibc's behavior.  This is currently working only on x86 with SSE."
    }
  },
  "baremetal": {
    "LIBC_COPT_BAREMETAL_HEAP_ENABLE_FREESTORE_ROTATION": {
      "value": false,
      "doc": "Enable rotational dual freestore in FreeListHeap to delay reuse of freed memory. This, when combined with sanitizers, helps detect Use-After-Free (UAF) bugs more reliably by preventing rapid reallocation of recently freed blocks. It costs one extra flag bit in the block header, which doubles the minimum allocation alignment on 32-bit targets."
    }
  },
  "assert": {
    "LIBC_COPT_USE_C_ASSERT": {
      "value": false,
      "doc": "Use the system assert macro for LIBC_ASSERT."
    },
    "LIBC_COPT_HARDENING_MODE": {
      "value": "LIBC_HARDENING_MODE_NONE",
      "doc": "Hardening mode for the library."
    }
  }
}