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[thirdparty/systemd.git] / src / basic / macro.h

/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once

#include <assert.h>
#include <errno.h>
#include <inttypes.h>
#include <stdbool.h>
#include <sys/param.h>
#include <sys/sysmacros.h>
#include <sys/types.h>

#include "constants.h"
#include "macro-fundamental.h"

/* Note: on GCC "no_sanitize_address" is a function attribute only, on llvm it may also be applied to global
 * variables. We define a specific macro which knows this. Note that on GCC we don't need this decorator so much, since
 * our primary use case for this attribute is registration structures placed in named ELF sections which shall not be
 * padded, but GCC doesn't pad those anyway if AddressSanitizer is enabled. */
#if HAS_FEATURE_ADDRESS_SANITIZER && defined(__clang__)
#define _variable_no_sanitize_address_ __attribute__((__no_sanitize_address__))
#else
#define _variable_no_sanitize_address_
#endif

/* Apparently there's no has_feature() call defined to check for ubsan, hence let's define this
 * unconditionally on llvm */
#if defined(__clang__)
#define _function_no_sanitize_float_cast_overflow_ __attribute__((no_sanitize("float-cast-overflow")))
#else
#define _function_no_sanitize_float_cast_overflow_
#endif

#if HAVE_WSTRINGOP_TRUNCATION
#  define DISABLE_WARNING_STRINGOP_TRUNCATION                           \
        _Pragma("GCC diagnostic push");                                 \
        _Pragma("GCC diagnostic ignored \"-Wstringop-truncation\"")
#else
#  define DISABLE_WARNING_STRINGOP_TRUNCATION                           \
        _Pragma("GCC diagnostic push")
#endif

/* test harness */
#define EXIT_TEST_SKIP 77

/* builtins */
#if __SIZEOF_INT__ == 4
#define BUILTIN_FFS_U32(x) __builtin_ffs(x);
#elif __SIZEOF_LONG__ == 4
#define BUILTIN_FFS_U32(x) __builtin_ffsl(x);
#else
#error "neither int nor long are four bytes long?!?"
#endif

static inline uint64_t u64_multiply_safe(uint64_t a, uint64_t b) {
        if (_unlikely_(a != 0 && b > (UINT64_MAX / a)))
                return 0; /* overflow */

        return a * b;
}

/* align to next higher power-of-2 (except for: 0 => 0, overflow => 0) */
static inline unsigned long ALIGN_POWER2(unsigned long u) {

        /* Avoid subtraction overflow */
        if (u == 0)
                return 0;

        /* clz(0) is undefined */
        if (u == 1)
                return 1;

        /* left-shift overflow is undefined */
        if (__builtin_clzl(u - 1UL) < 1)
                return 0;

        return 1UL << (sizeof(u) * 8 - __builtin_clzl(u - 1UL));
}

static inline size_t GREEDY_ALLOC_ROUND_UP(size_t l) {
        size_t m;

        /* Round up allocation sizes a bit to some reasonable, likely larger value. This is supposed to be
         * used for cases which are likely called in an allocation loop of some form, i.e. that repetitively
         * grow stuff, for example strv_extend() and suchlike.
         *
         * Note the difference to GREEDY_REALLOC() here, as this helper operates on a single size value only,
         * and rounds up to next multiple of 2, needing no further counter.
         *
         * Note the benefits of direct ALIGN_POWER2() usage: type-safety for size_t, sane handling for very
         * small (i.e. <= 2) and safe handling for very large (i.e. > SSIZE_MAX) values. */

        if (l <= 2)
                return 2; /* Never allocate less than 2 of something.  */

        m = ALIGN_POWER2(l);
        if (m == 0) /* overflow? */
                return l;

        return m;
}

/*
 * container_of - cast a member of a structure out to the containing structure
 * @ptr: the pointer to the member.
 * @type: the type of the container struct this is embedded in.
 * @member: the name of the member within the struct.
 */
#define container_of(ptr, type, member) __container_of(UNIQ, (ptr), type, member)
#define __container_of(uniq, ptr, type, member)                         \
        ({                                                              \
                const typeof( ((type*)0)->member ) *UNIQ_T(A, uniq) = (ptr); \
                (type*)( (char *)UNIQ_T(A, uniq) - offsetof(type, member) ); \
        })

#ifdef __COVERITY__

/* Use special definitions of assertion macros in order to prevent
 * false positives of ASSERT_SIDE_EFFECT on Coverity static analyzer
 * for uses of assert_se() and assert_return().
 *
 * These definitions make expression go through a (trivial) function
 * call to ensure they are not discarded. Also use ! or !! to ensure
 * the boolean expressions are seen as such.
 *
 * This technique has been described and recommended in:
 * https://community.synopsys.com/s/question/0D534000046Yuzb/suppressing-assertsideeffect-for-functions-that-allow-for-sideeffects
 */

extern void __coverity_panic__(void);

static inline void __coverity_check__(int condition) {
        if (!condition)
                __coverity_panic__();
}

static inline int __coverity_check_and_return__(int condition) {
        return condition;
}

#define assert_message_se(expr, message) __coverity_check__(!!(expr))

#define assert_log(expr, message) __coverity_check_and_return__(!!(expr))

#else  /* ! __COVERITY__ */

#define assert_message_se(expr, message)                                \
        do {                                                            \
                if (_unlikely_(!(expr)))                                \
                        log_assert_failed(message, PROJECT_FILE, __LINE__, __func__); \
        } while (false)

#define assert_log(expr, message) ((_likely_(expr))                     \
        ? (true)                                                        \
        : (log_assert_failed_return(message, PROJECT_FILE, __LINE__, __func__), false))

#endif  /* __COVERITY__ */

#define assert_se(expr) assert_message_se(expr, #expr)

/* We override the glibc assert() here. */
#undef assert
#ifdef NDEBUG
#define assert(expr) ({ if (!(expr)) __builtin_unreachable(); })
#else
#define assert(expr) assert_message_se(expr, #expr)
#endif

#define assert_not_reached()                                            \
        log_assert_failed_unreachable(PROJECT_FILE, __LINE__, __func__)

#define assert_return(expr, r)                                          \
        do {                                                            \
                if (!assert_log(expr, #expr))                           \
                        return (r);                                     \
        } while (false)

#define assert_return_errno(expr, r, err)                               \
        do {                                                            \
                if (!assert_log(expr, #expr)) {                         \
                        errno = err;                                    \
                        return (r);                                     \
                }                                                       \
        } while (false)

#define return_with_errno(r, err)                     \
        do {                                          \
                errno = abs(err);                     \
                return r;                             \
        } while (false)

#define PTR_TO_INT(p) ((int) ((intptr_t) (p)))
#define INT_TO_PTR(u) ((void *) ((intptr_t) (u)))
#define PTR_TO_UINT(p) ((unsigned) ((uintptr_t) (p)))
#define UINT_TO_PTR(u) ((void *) ((uintptr_t) (u)))

#define PTR_TO_LONG(p) ((long) ((intptr_t) (p)))
#define LONG_TO_PTR(u) ((void *) ((intptr_t) (u)))
#define PTR_TO_ULONG(p) ((unsigned long) ((uintptr_t) (p)))
#define ULONG_TO_PTR(u) ((void *) ((uintptr_t) (u)))

#define PTR_TO_UINT8(p) ((uint8_t) ((uintptr_t) (p)))
#define UINT8_TO_PTR(u) ((void *) ((uintptr_t) (u)))

#define PTR_TO_INT32(p) ((int32_t) ((intptr_t) (p)))
#define INT32_TO_PTR(u) ((void *) ((intptr_t) (u)))
#define PTR_TO_UINT32(p) ((uint32_t) ((uintptr_t) (p)))
#define UINT32_TO_PTR(u) ((void *) ((uintptr_t) (u)))

#define PTR_TO_INT64(p) ((int64_t) ((intptr_t) (p)))
#define INT64_TO_PTR(u) ((void *) ((intptr_t) (u)))
#define PTR_TO_UINT64(p) ((uint64_t) ((uintptr_t) (p)))
#define UINT64_TO_PTR(u) ((void *) ((uintptr_t) (u)))

#define PTR_TO_SIZE(p) ((size_t) ((uintptr_t) (p)))
#define SIZE_TO_PTR(u) ((void *) ((uintptr_t) (u)))

#define CHAR_TO_STR(x) ((char[2]) { x, 0 })

#define char_array_0(x) x[sizeof(x)-1] = 0;

#define sizeof_field(struct_type, member) sizeof(((struct_type *) 0)->member)
#define endoffsetof_field(struct_type, member) (offsetof(struct_type, member) + sizeof_field(struct_type, member))

/* Maximum buffer size needed for formatting an unsigned integer type as hex, including space for '0x'
 * prefix and trailing NUL suffix. */
#define HEXADECIMAL_STR_MAX(type) (2 + sizeof(type) * 2 + 1)

/* Returns the number of chars needed to format variables of the specified type as a decimal string. Adds in
 * extra space for a negative '-' prefix for signed types. Includes space for the trailing NUL. */
#define DECIMAL_STR_MAX(type)                                           \
        ((size_t) IS_SIGNED_INTEGER_TYPE(type) + 1U +                   \
            (sizeof(type) <= 1 ? 3U :                                   \
             sizeof(type) <= 2 ? 5U :                                   \
             sizeof(type) <= 4 ? 10U :                                  \
             sizeof(type) <= 8 ? (IS_SIGNED_INTEGER_TYPE(type) ? 19U : 20U) : sizeof(int[-2*(sizeof(type) > 8)])))

/* Returns the number of chars needed to format the specified integer value. It's hence more specific than
 * DECIMAL_STR_MAX() which answers the same question for all possible values of the specified type. Does
 * *not* include space for a trailing NUL. (If you wonder why we special case _x_ == 0 here: it's to trick
 * out gcc's -Wtype-limits, which would complain on comparing an unsigned type with < 0, otherwise. By
 * special-casing == 0 here first, we can use <= 0 instead of < 0 to trick out gcc.) */
#define DECIMAL_STR_WIDTH(x)                                      \
        ({                                                        \
                typeof(x) _x_ = (x);                              \
                size_t ans;                                       \
                if (_x_ == 0)                                     \
                        ans = 1;                                  \
                else {                                            \
                        ans = _x_ <= 0 ? 2 : 1;                   \
                        while ((_x_ /= 10) != 0)                  \
                                ans++;                            \
                }                                                 \
                ans;                                              \
        })

#define SWAP_TWO(x, y) do {                        \
                typeof(x) _t = (x);                \
                (x) = (y);                         \
                (y) = (_t);                        \
        } while (false)

#define STRV_MAKE(...) ((char**) ((const char*[]) { __VA_ARGS__, NULL }))
#define STRV_MAKE_EMPTY ((char*[1]) { NULL })
#define STRV_MAKE_CONST(...) ((const char* const*) ((const char*[]) { __VA_ARGS__, NULL }))

/* Pointers range from NULL to POINTER_MAX */
#define POINTER_MAX ((void*) UINTPTR_MAX)

#define _FOREACH_ARRAY(i, array, num, m, end)                           \
        for (typeof(array[0]) *i = (array), *end = ({                   \
                                typeof(num) m = (num);                  \
                                (i && m > 0) ? i + m : NULL;            \
                        }); end && i < end; i++)

#define FOREACH_ARRAY(i, array, num)                                    \
        _FOREACH_ARRAY(i, array, num, UNIQ_T(m, UNIQ), UNIQ_T(end, UNIQ))

#define FOREACH_ELEMENT(i, array)                                 \
        FOREACH_ARRAY(i, array, ELEMENTSOF(array))

#define _DEFINE_TRIVIAL_REF_FUNC(type, name, scope)             \
        scope type *name##_ref(type *p) {                       \
                if (!p)                                         \
                        return NULL;                            \
                                                                \
                /* For type check. */                           \
                unsigned *q = &p->n_ref;                        \
                assert(*q > 0);                                 \
                assert_se(*q < UINT_MAX);                       \
                                                                \
                (*q)++;                                         \
                return p;                                       \
        }

#define _DEFINE_TRIVIAL_UNREF_FUNC(type, name, free_func, scope) \
        scope type *name##_unref(type *p) {                      \
                if (!p)                                          \
                        return NULL;                             \
                                                                 \
                assert(p->n_ref > 0);                            \
                p->n_ref--;                                      \
                if (p->n_ref > 0)                                \
                        return NULL;                             \
                                                                 \
                return free_func(p);                             \
        }

#define DEFINE_TRIVIAL_REF_FUNC(type, name)     \
        _DEFINE_TRIVIAL_REF_FUNC(type, name,)
#define DEFINE_PRIVATE_TRIVIAL_REF_FUNC(type, name)     \
        _DEFINE_TRIVIAL_REF_FUNC(type, name, static)
#define DEFINE_PUBLIC_TRIVIAL_REF_FUNC(type, name)      \
        _DEFINE_TRIVIAL_REF_FUNC(type, name, _public_)

#define DEFINE_TRIVIAL_UNREF_FUNC(type, name, free_func)        \
        _DEFINE_TRIVIAL_UNREF_FUNC(type, name, free_func,)
#define DEFINE_PRIVATE_TRIVIAL_UNREF_FUNC(type, name, free_func)        \
        _DEFINE_TRIVIAL_UNREF_FUNC(type, name, free_func, static)
#define DEFINE_PUBLIC_TRIVIAL_UNREF_FUNC(type, name, free_func)         \
        _DEFINE_TRIVIAL_UNREF_FUNC(type, name, free_func, _public_)

#define DEFINE_TRIVIAL_REF_UNREF_FUNC(type, name, free_func)    \
        DEFINE_TRIVIAL_REF_FUNC(type, name);                    \
        DEFINE_TRIVIAL_UNREF_FUNC(type, name, free_func);

#define DEFINE_PRIVATE_TRIVIAL_REF_UNREF_FUNC(type, name, free_func)    \
        DEFINE_PRIVATE_TRIVIAL_REF_FUNC(type, name);                    \
        DEFINE_PRIVATE_TRIVIAL_UNREF_FUNC(type, name, free_func);

#define DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(type, name, free_func)    \
        DEFINE_PUBLIC_TRIVIAL_REF_FUNC(type, name);                    \
        DEFINE_PUBLIC_TRIVIAL_UNREF_FUNC(type, name, free_func);

/* A macro to force copying of a variable from memory. This is useful whenever we want to read something from
 * memory and want to make sure the compiler won't optimize away the destination variable for us. It's not
 * supposed to be a full CPU memory barrier, i.e. CPU is still allowed to reorder the reads, but it is not
 * allowed to remove our local copies of the variables. We want this to work for unaligned memory, hence
 * memcpy() is great for our purposes. */
#define READ_NOW(x)                                                     \
        ({                                                              \
                typeof(x) _copy;                                        \
                memcpy(&_copy, &(x), sizeof(_copy));                    \
                asm volatile ("" : : : "memory");                       \
                _copy;                                                  \
        })

#define saturate_add(x, y, limit)                                       \
        ({                                                              \
                typeof(limit) _x = (x);                                 \
                typeof(limit) _y = (y);                                 \
                _x > (limit) || _y >= (limit) - _x ? (limit) : _x + _y; \
        })

static inline size_t size_add(size_t x, size_t y) {
        return saturate_add(x, y, SIZE_MAX);
}

typedef struct {
        int _empty[0];
} dummy_t;

assert_cc(sizeof(dummy_t) == 0);

/* A little helper for subtracting 1 off a pointer in a safe UB-free way. This is intended to be used for
 * loops that count down from a high pointer until some base. A naive loop would implement this like this:
 *
 * for (p = end-1; p >= base; p--) …
 *
 * But this is not safe because p before the base is UB in C. With this macro the loop becomes this instead:
 *
 * for (p = PTR_SUB1(end, base); p; p = PTR_SUB1(p, base)) …
 *
 * And is free from UB! */
#define PTR_SUB1(p, base)                                \
        ({                                               \
                typeof(p) _q = (p);                      \
                _q && _q > (base) ? &_q[-1] : NULL;      \
        })

/* Iterate through each argument passed. All must be the same type as 'entry' or must be implicitly
 * convertible. The iteration variable 'entry' must already be defined. */
#define FOREACH_ARGUMENT(entry, ...)                                     \
        _FOREACH_ARGUMENT(entry, UNIQ_T(_entries_, UNIQ), UNIQ_T(_current_, UNIQ), UNIQ_T(_va_sentinel_, UNIQ), ##__VA_ARGS__)
#define _FOREACH_ARGUMENT(entry, _entries_, _current_, _va_sentinel_, ...)      \
        for (typeof(entry) _va_sentinel_[1] = {}, _entries_[] = { __VA_ARGS__ __VA_OPT__(,) _va_sentinel_[0] }, *_current_ = _entries_; \
             ((long)(_current_ - _entries_) < (long)(ELEMENTSOF(_entries_) - 1)) && ({ entry = *_current_; true; }); \
             _current_++)

#define DECIMAL_STR_FMT(x) _Generic((x),        \
        char: "%c",                             \
        bool: "%d",                             \
        unsigned char: "%d",                    \
        short: "%hd",                           \
        unsigned short: "%hu",                  \
        int: "%d",                              \
        unsigned: "%u",                         \
        long: "%ld",                            \
        unsigned long: "%lu",                   \
        long long: "%lld",                      \
        unsigned long long: "%llu")

#include "log.h"