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memchr memcmp memcpy memcpy_s memmove memmove_s memset memset_s Null-terminated byte strings Null-terminated multibyte strings Null-terminated wide strings strcat strcat_s strchr strcmp strcoll strcpy strcpy_s strcspn strerror strerrorlen_s strerror_s Strings library strlen strncat Thread support call_once cnd_broadcast cnd_destroy cnd_init cnd_signal cnd_timedwait cnd_wait mtx_destroy mtx_init mtx_lock mtx_plain mtx_recursive mtx_timed mtx_timedlock mtx_trylock mtx_unlock once_flag ONCE_FLAG_INIT thrd_busy thrd_create thrd_current thrd_detach thrd_equal thrd_error thrd_exit thrd_join thrd_nomem thrd_sleep thrd_success thrd_timedout thrd_yield Thread support library thread_local tss_create tss_delete TSS_DTOR_ITERATIONS tss_get tss_set Type support Boolean type support library Fixed width integer types FLT_EVAL_METHOD FLT_ROUNDS max_align_t NULL Numeric limits offsetof ptrdiff_t size_t Type support Variadic functions Variadic functions va_arg va_copy va_end va_list va_start
characters

在头文件中定义



typedef / *实现定义* / float_t


(自C99以来)

typedef / *实现定义* / double_t


(自C99以来)

float_t和double_t类型的浮点类型至少与float和double一样宽,并且double_t至少与float_t一样宽。 FLT_EVAL_METHOD的值决定了float_t和double_t的类型。

FLT_EVAL_METHOD

说明

0

float_t和double_t分别等价于float和double

1

float_t和double_t都相当于double

2

float_t和double_t都相当于long double

其他

float_t和double_t都是实现定义的

#include #include #include  int main(void){ printf("%d\n", FLT_EVAL_METHOD); printf("%zu %zu\n", sizeof(float),sizeof(float_t)); printf("%zu %zu\n", sizeof(double),sizeof(double_t)); return 0;}

可能的输出:

04 48 8

参考

  • C11标准(ISO / IEC 9899:2011):

    • 7.12 (p:231)

  • C99标准(ISO / IEC 9899:1999):

    • 7.12 (p:212)

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