Build failed for a baremetal

git.morello-project.org/.../standalone-baremetal-readme.rst

N.B: Since it is a standalone baremetal program I already commented out the print statements and I have enclosed the cheri.h file code below. This header file is already provided in the sample example of ARM MORELLO.

============bubblesort.c   code below====================================

//==========bubblesort=============

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <time.h>
#include "cheri.h"


#define seq_t uint32_t*__capability

// The __capability qualifier here is not necessary when compiling for "pure" mode
// (because all pointers have capabilities in "pure" mode), but might be needed
// if compiling for "hybrid" mode, so has been left in for convenience and clarity.

#define SEQ_LEN 15

void populate (seq_t __cheri_output sequence, int size);
void sort (seq_t sequence, int size);
void swap (seq_t first, seq_t second);


int main (void) {
    //printf("Morello bare-metal bubble sort example\n\n");

    seq_t sequence = (__cheri_tocap seq_t)malloc(sizeof(uint32_t) * SEQ_LEN);

    populate(sequence, SEQ_LEN);

    //printf("Original sequence:\n  ");
    //print(sequence, SEQ_LEN);

    sort(sequence, SEQ_LEN);

    //printf("Sorted sequence:\n  ");
    //print(sequence, SEQ_LEN);

    free((__cheri_fromcap void*)sequence);

    return 0;
}

void populate (seq_t __cheri_output sequence, int size) {
    srand(time(NULL));

    for (int i = 0; i < size; i++) {
        sequence[i] = rand() % (101);
    }
}


void sort (seq_t sequence, int size) {
    for (int i = 0; i < (size - 1); i++) {
        for (int j = 0; j < (size - i - 1); j++) {
            if (sequence[j] > sequence[j+1]) {
                swap(&sequence[j], &sequence[j+1]);
            }
        }
    }
}

void swap (seq_t first, seq_t second) {
    uint32_t temp = *first;
    *first = *second;
    *second = temp;
}

=============== cheri.h  code below ======================================

/*===---- cheri.h - Header for CHERI capabilities -----------------------===*\
 *
 * Copyright (c) 2014 David Chisnall
 * Copyright (c) 2018 Alex Richardson
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
\*===----------------------------------------------------------------------===*/
#ifndef _CHERI_H
#define _CHERI_H

#pragma once

#ifdef __aarch64__
typedef unsigned int cheri_perms_t;
#else
typedef unsigned short cheri_perms_t;
#endif
typedef unsigned short cheri_flags_t;
typedef unsigned __INT32_TYPE__ cheri_type_t;
#ifdef __cplusplus
#define __cheri_bool bool
#else
#define __cheri_bool _Bool
#endif

#if __has_feature(capabilities)
#define __IF_CAPS(x, y) x
typedef __intcap_t intcap_t;
typedef __uintcap_t uintcap_t;
#ifdef WANT_CHERI_QUALIFIER_MACROS
#define capability __capability
#define output __cheri_output
#define input __cheri_input
#endif
#else
#define __IF_CAPS(x, y) y
typedef __INTPTR_TYPE__ intcap_t;
typedef __UINTPTR_TYPE__ uintcap_t;
#define __capability
#ifdef WANT_CHERI_QUALIFIER_MACROS
#define capability
#define output
#define input
#endif
#endif

#define __CHERI_GET(__name, __type, __get, __default)            \
  static inline __type                                                        \
  cheri_##__name##__get(void * __capability __cap)                              \
  {                                                                           \
    return __IF_CAPS(__builtin_cheri_##__name##__get(__cap), __default);     \
  }

#define __CHERI_SET(__name, __type, __set)                                     \
  static inline void *__capability cheri_##__name##__set(                      \
      void *__capability __cap, __type __val) {                                \
    return __IF_CAPS(__builtin_cheri_##__name##__set(__cap, __val),            \
                     (void *)__cap);                                           \
  }

#define __CHERI_ACCESSOR(__name, __type, __set, __get, __default)            \
  __CHERI_GET(__name, __type, __get, __default)                              \
  __CHERI_SET(__name, __type, __set)                                         \

__CHERI_GET(length, __SIZE_TYPE__, _get, __SIZE_MAX__)
__CHERI_GET(base, __SIZE_TYPE__, _get, __SIZE_MAX__)
__CHERI_ACCESSOR(offset, __SIZE_TYPE__, _set, _get, __SIZE_MAX__)
__CHERI_GET(type, cheri_type_t, _get, 0)
__CHERI_ACCESSOR(perms, cheri_perms_t, _and, _get, 0)
__CHERI_ACCESSOR(flags, cheri_flags_t, _set, _get, 0)
__CHERI_GET(tag, __cheri_bool, _get, 0)
__CHERI_GET(sealed, __cheri_bool, _get, 0)

static inline
void * __capability cheri_offset_increment(void *__capability __cap,
                                         __PTRDIFF_TYPE__ __offset) {
  return __IF_CAPS(__builtin_cheri_offset_increment(__cap, __offset),
                   ((char*)__cap) + __offset);
}

static inline
void * __capability cheri_tag_clear(void * __capability __cap) {
  return __IF_CAPS(__builtin_cheri_tag_clear(__cap), (void*)__cap);
}

static inline
void * __capability cheri_seal(void * __capability __cap,
                               const void * __capability __type) {
  return __IF_CAPS(__builtin_cheri_seal(__cap, __type), (void*)__cap);
}

static inline
void * __capability cheri_unseal(void * __capability __cap,
                                 const void * __capability __type) {
  return __IF_CAPS(__builtin_cheri_unseal(__cap, __type), (void*)__cap);
}

static inline
void * __capability cheri_bounds_set(void *__capability __cap,
                                   __SIZE_TYPE__ __bounds) {
  return __IF_CAPS(__builtin_cheri_bounds_set(__cap, __bounds), (void*)__cap);
}

static inline
__SIZE_TYPE__ cheri_round_representable_length(__SIZE_TYPE__ __length) {
  return __IF_CAPS(__builtin_cheri_round_representable_length(__length), __length);
}

static inline
__SIZE_TYPE__ cheri_round_representable_mask(__SIZE_TYPE__ __mask) {
  return __IF_CAPS(__builtin_cheri_representable_alignment_mask(__mask), __mask);
}

static inline
__SIZE_TYPE__ cheri_copy_from_high(void *__capability __cap) {
  return __IF_CAPS(__builtin_cheri_copy_from_high(__cap), __SIZE_MAX__);
}

static inline
void * __capability
cheri_copy_to_high(const void *__capability __cap, __SIZE_TYPE__ __high) {
  return __IF_CAPS(__builtin_cheri_copy_to_high(__cap, __high), (void*)__cap);
}

static inline __SIZE_TYPE__ cheri_equal_exact(const void * __capability __cap_a,
    const void * __capability __cap_b) {
  return __IF_CAPS(__builtin_cheri_equal_exact(__cap_a, __cap_b), 0);
}

static inline __SIZE_TYPE__ cheri_subset_test(const void * __capability __cap_a,
    const void * __capability __cap_b) {
  return __IF_CAPS(__builtin_cheri_subset_test(__cap_a, __cap_b), 0);
}

#ifndef __CHERI_PURE_CAPABILITY__
static inline
void * __capability
cheri_cap_from_pointer(const void * __capability __cap, void *__ptr) {
  return __IF_CAPS(__builtin_cheri_cap_from_pointer(__cap, __ptr),
                   (void *)__ptr);
}

static inline
void * cheri_cap_to_pointer(const void * __capability __cap,
                            void * __capability __offset) {
  return __IF_CAPS(__builtin_cheri_cap_to_pointer(__cap, __offset),
                   (void *)__offset);
}
#endif

static inline
void cheri_perms_check(const void * __capability __cap, cheri_perms_t __perms) {
  __IF_CAPS(__builtin_cheri_perms_check(__cap, __perms), );
}

static inline
void cheri_type_check(const void * __capability __cap,
                      const void * __capability __type) {
  __IF_CAPS(__builtin_cheri_type_check(__cap, __type), );
}

static inline
void * __capability cheri_global_data_get(void) {
  return __IF_CAPS(__builtin_cheri_global_data_get(), 0);
}

static inline
void * __capability cheri_program_counter_get(void) {
  return __IF_CAPS(__builtin_cheri_program_counter_get(), 0);
}

/* TODO: Should these be builtins to get better diagnostics? */

static inline __attribute__((always_inline)) __attribute__((warn_unused_result))
__PTRADDR_TYPE__
__cheri_low_bits_get(uintcap_t ptr, __PTRADDR_TYPE__ mask) {
  /*
   * We need to return a NULL-derived capability here, so we need to explicitly
   * cast the LHS to a non-capability integer.
   */
  return (__PTRADDR_TYPE__)ptr & mask;
}

static inline __attribute__((always_inline)) __attribute__((warn_unused_result))
uintcap_t
__cheri_low_bits_or(uintcap_t ptr, __PTRADDR_TYPE__ bits) {
  /*
   * We want to return a LHS-derived capability here so using the default
   * uintcap_t semantics is fine.
   */
  return ptr | bits;
}

static inline __attribute__((always_inline)) __attribute__((warn_unused_result))
uintcap_t
__cheri_low_bits_clear(uintcap_t ptr, __PTRADDR_TYPE__ bits_mask) {
  /*
   * We want to return a LHS-derived capability here so using the default
   * uintcap_t semantics is fine.
   */
  return ptr & (~bits_mask);
}

#ifndef __cheri_usable_low_bits_mask
#define __cheri_usable_low_bits_mask 31
#endif
#define __static_assert_sensible_low_bits(bits)                                \
  __extension__({                                                              \
    _Static_assert(bits < (__cheri_usable_low_bits_mask + 1),                  \
                   "Using too many low pointer bits");                         \
    _Static_assert((bits & (bits + 1)) == 0, "Mask must be all ones");         \
    (__PTRADDR_TYPE__)(bits);                                                  \
  })
#define __runtime_assert_sensible_low_bits(bits, mask)                         \
  __extension__({                                                              \
    __PTRADDR_TYPE__ _bits = (__PTRADDR_TYPE__)(bits);                         \
    __PTRADDR_TYPE__ _mask = __static_assert_sensible_low_bits(mask);          \
    assert(((_bits & _mask) == _bits) && "Bits outside mask used!");           \
    _bits;                                                                     \
  })

/*
 * Get the low bits defined in @p mask from the capability/pointer @p ptr.
 * @p mask must be a compile-time constant less than 31.
 * TODO: should we allow non-constant masks?
 *
 * @param ptr the uintptr_t that may have low bits sets
 * @param mask the mask for the low pointer bits to retrieve
 * @return a size_t containing the the low bits from @p ptr
 *
 * Rationale: this function is needed because extracting the low bits using a
 * bitwise-and operation returns a LHS-derived capability with the offset
 * field set to LHS.offset & mask. This is almost certainly not what the user
 * wanted since it will always compare not equal to any integer constant.
 * For example lots of mutex code uses something like `if ((x & 1) == 1)` to
 * detect if the lock is currently contented. This comparison always returns
 * false under CHERI the LHS of the == is a valid capability with offset 3 and
 * the RHS is an untagged intcap_t with offset 3.
 * See https://github.com/CTSRD-CHERI/clang/issues/189
 */
#define cheri_low_bits_get(ptr, mask)                                          \
  __cheri_low_bits_get(ptr, __static_assert_sensible_low_bits(mask))

/*
 * Bitwise-OR of low bits in a uintptr_t
 *
 * @param ptr the uintptr_t that may have low bits sets
 * @param bits the value to bitwise-or with @p ptr.
 * @return a uintptr_t that has the low bits  @p bits
 *
 * @note this function is not strictly required since a plain bitwise or will
 * generally give the behaviour that is expected from other platforms.
 * However, we can't really make the warning "-Wcheri-bitwise-operations"
 * trigger based on of the right hand side expression since it may not be a
 * compile-time constant.
 */
#define cheri_low_bits_or(ptr, bits)                                           \
  __cheri_low_bits_or(ptr, __runtime_assert_sensible_low_bits(                 \
                               bits, __cheri_usable_low_bits_mask))

/*
 * Set low bits in a uintptr_t
 *
 * @param ptr the uintptr_t that may have low bits sets
 * @param mask the mask for the low pointer bits to be cleared before setting
 * them to @p bits.
 * @param bits the value to bitwise-or with @p ptr.
 * @return a uintptr_t that has the low bits defined in @p mask set to @p bits
 *
 * @note this function is not strictly required since a plain bitwise or will
 * generally give the behaviour that is expected from other platforms.
 * However, we can't really make the warning "-Wcheri-bitwise-operations"
 * trigger based on of the right hand side expression since it may not be a
 * compile-time constant.
 */
#define cheri_low_bits_set(ptr, mask, bits)                                    \
  __cheri_low_bits_or(cheri_low_bits_clear(ptr, mask),                         \
                      __runtime_assert_sensible_low_bits(bits, mask))

/*
 * Clear the bits in @p mask from the capability/pointer @p ptr. Mask must be
 * a compile-time constant less than 31
 *
 * TODO: should we allow non-constant masks?
 *
 * @param ptr the uintptr_t that may have low bits sets
 * @param mask this is the mask for the low pointer bits, not the mask for
 * the bits that should remain set.
 * @return a uintptr_t that has the low bits defined in @p mask set to zeroes
 *
 *
 */
#define cheri_low_bits_clear(ptr, mask)                                        \
  __cheri_low_bits_clear(ptr, __static_assert_sensible_low_bits(mask))

#undef __CHERI_ACCESSOR
#undef __CHERI_GET
#undef __CHERI_SET
#undef __cheri_bool
#undef __IF_CAPS

#endif /* _CHERI_H */

git.morello-project.org/.../standalone-baremetal-readme.rst

N.B: Since it is a standalone baremetal program I already commented out the print statements and I have enclosed the cheri.h file code below. This header file is already provided in the sample example of ARM MORELLO.

============bubblesort.c   code below====================================

//==========bubblesort=============

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <time.h>
#include "cheri.h"


#define seq_t uint32_t*__capability

// The __capability qualifier here is not necessary when compiling for "pure" mode
// (because all pointers have capabilities in "pure" mode), but might be needed
// if compiling for "hybrid" mode, so has been left in for convenience and clarity.

#define SEQ_LEN 15

void populate (seq_t __cheri_output sequence, int size);
void sort (seq_t sequence, int size);
void swap (seq_t first, seq_t second);


int main (void) {
    //printf("Morello bare-metal bubble sort example\n\n");

    seq_t sequence = (__cheri_tocap seq_t)malloc(sizeof(uint32_t) * SEQ_LEN);

    populate(sequence, SEQ_LEN);

    //printf("Original sequence:\n  ");
    //print(sequence, SEQ_LEN);

    sort(sequence, SEQ_LEN);

    //printf("Sorted sequence:\n  ");
    //print(sequence, SEQ_LEN);

    free((__cheri_fromcap void*)sequence);

    return 0;
}

void populate (seq_t __cheri_output sequence, int size) {
    srand(time(NULL));

    for (int i = 0; i < size; i++) {
        sequence[i] = rand() % (101);
    }
}


void sort (seq_t sequence, int size) {
    for (int i = 0; i < (size - 1); i++) {
        for (int j = 0; j < (size - i - 1); j++) {
            if (sequence[j] > sequence[j+1]) {
                swap(&sequence[j], &sequence[j+1]);
            }
        }
    }
}

void swap (seq_t first, seq_t second) {
    uint32_t temp = *first;
    *first = *second;
    *second = temp;
}

=============== cheri.h  code below ======================================

/*===---- cheri.h - Header for CHERI capabilities -----------------------===*\
 *
 * Copyright (c) 2014 David Chisnall
 * Copyright (c) 2018 Alex Richardson
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
\*===----------------------------------------------------------------------===*/
#ifndef _CHERI_H
#define _CHERI_H

#pragma once

#ifdef __aarch64__
typedef unsigned int cheri_perms_t;
#else
typedef unsigned short cheri_perms_t;
#endif
typedef unsigned short cheri_flags_t;
typedef unsigned __INT32_TYPE__ cheri_type_t;
#ifdef __cplusplus
#define __cheri_bool bool
#else
#define __cheri_bool _Bool
#endif

#if __has_feature(capabilities)
#define __IF_CAPS(x, y) x
typedef __intcap_t intcap_t;
typedef __uintcap_t uintcap_t;
#ifdef WANT_CHERI_QUALIFIER_MACROS
#define capability __capability
#define output __cheri_output
#define input __cheri_input
#endif
#else
#define __IF_CAPS(x, y) y
typedef __INTPTR_TYPE__ intcap_t;
typedef __UINTPTR_TYPE__ uintcap_t;
#define __capability
#ifdef WANT_CHERI_QUALIFIER_MACROS
#define capability
#define output
#define input
#endif
#endif

#define __CHERI_GET(__name, __type, __get, __default)            \
  static inline __type                                                        \
  cheri_##__name##__get(void * __capability __cap)                              \
  {                                                                           \
    return __IF_CAPS(__builtin_cheri_##__name##__get(__cap), __default);     \
  }

#define __CHERI_SET(__name, __type, __set)                                     \
  static inline void *__capability cheri_##__name##__set(                      \
      void *__capability __cap, __type __val) {                                \
    return __IF_CAPS(__builtin_cheri_##__name##__set(__cap, __val),            \
                     (void *)__cap);                                           \
  }

#define __CHERI_ACCESSOR(__name, __type, __set, __get, __default)            \
  __CHERI_GET(__name, __type, __get, __default)                              \
  __CHERI_SET(__name, __type, __set)                                         \

__CHERI_GET(length, __SIZE_TYPE__, _get, __SIZE_MAX__)
__CHERI_GET(base, __SIZE_TYPE__, _get, __SIZE_MAX__)
__CHERI_ACCESSOR(offset, __SIZE_TYPE__, _set, _get, __SIZE_MAX__)
__CHERI_GET(type, cheri_type_t, _get, 0)
__CHERI_ACCESSOR(perms, cheri_perms_t, _and, _get, 0)
__CHERI_ACCESSOR(flags, cheri_flags_t, _set, _get, 0)
__CHERI_GET(tag, __cheri_bool, _get, 0)
__CHERI_GET(sealed, __cheri_bool, _get, 0)

static inline
void * __capability cheri_offset_increment(void *__capability __cap,
                                         __PTRDIFF_TYPE__ __offset) {
  return __IF_CAPS(__builtin_cheri_offset_increment(__cap, __offset),
                   ((char*)__cap) + __offset);
}

static inline
void * __capability cheri_tag_clear(void * __capability __cap) {
  return __IF_CAPS(__builtin_cheri_tag_clear(__cap), (void*)__cap);
}

static inline
void * __capability cheri_seal(void * __capability __cap,
                               const void * __capability __type) {
  return __IF_CAPS(__builtin_cheri_seal(__cap, __type), (void*)__cap);
}

static inline
void * __capability cheri_unseal(void * __capability __cap,
                                 const void * __capability __type) {
  return __IF_CAPS(__builtin_cheri_unseal(__cap, __type), (void*)__cap);
}

static inline
void * __capability cheri_bounds_set(void *__capability __cap,
                                   __SIZE_TYPE__ __bounds) {
  return __IF_CAPS(__builtin_cheri_bounds_set(__cap, __bounds), (void*)__cap);
}

static inline
__SIZE_TYPE__ cheri_round_representable_length(__SIZE_TYPE__ __length) {
  return __IF_CAPS(__builtin_cheri_round_representable_length(__length), __length);
}

static inline
__SIZE_TYPE__ cheri_round_representable_mask(__SIZE_TYPE__ __mask) {
  return __IF_CAPS(__builtin_cheri_representable_alignment_mask(__mask), __mask);
}

static inline
__SIZE_TYPE__ cheri_copy_from_high(void *__capability __cap) {
  return __IF_CAPS(__builtin_cheri_copy_from_high(__cap), __SIZE_MAX__);
}

static inline
void * __capability
cheri_copy_to_high(const void *__capability __cap, __SIZE_TYPE__ __high) {
  return __IF_CAPS(__builtin_cheri_copy_to_high(__cap, __high), (void*)__cap);
}

static inline __SIZE_TYPE__ cheri_equal_exact(const void * __capability __cap_a,
    const void * __capability __cap_b) {
  return __IF_CAPS(__builtin_cheri_equal_exact(__cap_a, __cap_b), 0);
}

static inline __SIZE_TYPE__ cheri_subset_test(const void * __capability __cap_a,
    const void * __capability __cap_b) {
  return __IF_CAPS(__builtin_cheri_subset_test(__cap_a, __cap_b), 0);
}

#ifndef __CHERI_PURE_CAPABILITY__
static inline
void * __capability
cheri_cap_from_pointer(const void * __capability __cap, void *__ptr) {
  return __IF_CAPS(__builtin_cheri_cap_from_pointer(__cap, __ptr),
                   (void *)__ptr);
}

static inline
void * cheri_cap_to_pointer(const void * __capability __cap,
                            void * __capability __offset) {
  return __IF_CAPS(__builtin_cheri_cap_to_pointer(__cap, __offset),
                   (void *)__offset);
}
#endif

static inline
void cheri_perms_check(const void * __capability __cap, cheri_perms_t __perms) {
  __IF_CAPS(__builtin_cheri_perms_check(__cap, __perms), );
}

static inline
void cheri_type_check(const void * __capability __cap,
                      const void * __capability __type) {
  __IF_CAPS(__builtin_cheri_type_check(__cap, __type), );
}

static inline
void * __capability cheri_global_data_get(void) {
  return __IF_CAPS(__builtin_cheri_global_data_get(), 0);
}

static inline
void * __capability cheri_program_counter_get(void) {
  return __IF_CAPS(__builtin_cheri_program_counter_get(), 0);
}

/* TODO: Should these be builtins to get better diagnostics? */

static inline __attribute__((always_inline)) __attribute__((warn_unused_result))
__PTRADDR_TYPE__
__cheri_low_bits_get(uintcap_t ptr, __PTRADDR_TYPE__ mask) {
  /*
   * We need to return a NULL-derived capability here, so we need to explicitly
   * cast the LHS to a non-capability integer.
   */
  return (__PTRADDR_TYPE__)ptr & mask;
}

static inline __attribute__((always_inline)) __attribute__((warn_unused_result))
uintcap_t
__cheri_low_bits_or(uintcap_t ptr, __PTRADDR_TYPE__ bits) {
  /*
   * We want to return a LHS-derived capability here so using the default
   * uintcap_t semantics is fine.
   */
  return ptr | bits;
}

static inline __attribute__((always_inline)) __attribute__((warn_unused_result))
uintcap_t
__cheri_low_bits_clear(uintcap_t ptr, __PTRADDR_TYPE__ bits_mask) {
  /*
   * We want to return a LHS-derived capability here so using the default
   * uintcap_t semantics is fine.
   */
  return ptr & (~bits_mask);
}

#ifndef __cheri_usable_low_bits_mask
#define __cheri_usable_low_bits_mask 31
#endif
#define __static_assert_sensible_low_bits(bits)                                \
  __extension__({                                                              \
    _Static_assert(bits < (__cheri_usable_low_bits_mask + 1),                  \
                   "Using too many low pointer bits");                         \
    _Static_assert((bits & (bits + 1)) == 0, "Mask must be all ones");         \
    (__PTRADDR_TYPE__)(bits);                                                  \
  })
#define __runtime_assert_sensible_low_bits(bits, mask)                         \
  __extension__({                                                              \
    __PTRADDR_TYPE__ _bits = (__PTRADDR_TYPE__)(bits);                         \
    __PTRADDR_TYPE__ _mask = __static_assert_sensible_low_bits(mask);          \
    assert(((_bits & _mask) == _bits) && "Bits outside mask used!");           \
    _bits;                                                                     \
  })

/*
 * Get the low bits defined in @p mask from the capability/pointer @p ptr.
 * @p mask must be a compile-time constant less than 31.
 * TODO: should we allow non-constant masks?
 *
 * @param ptr the uintptr_t that may have low bits sets
 * @param mask the mask for the low pointer bits to retrieve
 * @return a size_t containing the the low bits from @p ptr
 *
 * Rationale: this function is needed because extracting the low bits using a
 * bitwise-and operation returns a LHS-derived capability with the offset
 * field set to LHS.offset & mask. This is almost certainly not what the user
 * wanted since it will always compare not equal to any integer constant.
 * For example lots of mutex code uses something like `if ((x & 1) == 1)` to
 * detect if the lock is currently contented. This comparison always returns
 * false under CHERI the LHS of the == is a valid capability with offset 3 and
 * the RHS is an untagged intcap_t with offset 3.
 * See https://github.com/CTSRD-CHERI/clang/issues/189
 */
#define cheri_low_bits_get(ptr, mask)                                          \
  __cheri_low_bits_get(ptr, __static_assert_sensible_low_bits(mask))

/*
 * Bitwise-OR of low bits in a uintptr_t
 *
 * @param ptr the uintptr_t that may have low bits sets
 * @param bits the value to bitwise-or with @p ptr.
 * @return a uintptr_t that has the low bits  @p bits
 *
 * @note this function is not strictly required since a plain bitwise or will
 * generally give the behaviour that is expected from other platforms.
 * However, we can't really make the warning "-Wcheri-bitwise-operations"
 * trigger based on of the right hand side expression since it may not be a
 * compile-time constant.
 */
#define cheri_low_bits_or(ptr, bits)                                           \
  __cheri_low_bits_or(ptr, __runtime_assert_sensible_low_bits(                 \
                               bits, __cheri_usable_low_bits_mask))

/*
 * Set low bits in a uintptr_t
 *
 * @param ptr the uintptr_t that may have low bits sets
 * @param mask the mask for the low pointer bits to be cleared before setting
 * them to @p bits.
 * @param bits the value to bitwise-or with @p ptr.
 * @return a uintptr_t that has the low bits defined in @p mask set to @p bits
 *
 * @note this function is not strictly required since a plain bitwise or will
 * generally give the behaviour that is expected from other platforms.
 * However, we can't really make the warning "-Wcheri-bitwise-operations"
 * trigger based on of the right hand side expression since it may not be a
 * compile-time constant.
 */
#define cheri_low_bits_set(ptr, mask, bits)                                    \
  __cheri_low_bits_or(cheri_low_bits_clear(ptr, mask),                         \
                      __runtime_assert_sensible_low_bits(bits, mask))

/*
 * Clear the bits in @p mask from the capability/pointer @p ptr. Mask must be
 * a compile-time constant less than 31
 *
 * TODO: should we allow non-constant masks?
 *
 * @param ptr the uintptr_t that may have low bits sets
 * @param mask this is the mask for the low pointer bits, not the mask for
 * the bits that should remain set.
 * @return a uintptr_t that has the low bits defined in @p mask set to zeroes
 *
 *
 */
#define cheri_low_bits_clear(ptr, mask)                                        \
  __cheri_low_bits_clear(ptr, __static_assert_sensible_low_bits(mask))

#undef __CHERI_ACCESSOR
#undef __CHERI_GET
#undef __CHERI_SET
#undef __cheri_bool
#undef __IF_CAPS

#endif /* _CHERI_H */

https://cheri-compiler-explorer.cl.cam.ac.uk/z/5Ys3Pz

I suspect you are not actually enabling Morello, causing cheri.h to #define __capability to nothing. Make sure to pass -march=morello to Clang.