Every object in C exists, has a constant address, retains its last-stored value (except when the value is indeterminate), and, for VLA, retains its size (since C99) over a portion of program execution known as this object's lifetime. For the objects that are declared with automatic, static, and thread storage duration, lifetime equals their storage duration (note the difference between non-VLA and VLA automatic storage duration). For the objects with allocated storage duration, the lifetime beg

Defined in header <stdlib.h> float strtof( const char *restrict str, char **restrict str_end ); (since C99) double strtod( const char *str, char **str_end ); (until C99) double strtod( const char *restrict str, char **restrict str_end ); (since C99) long double strtold( const char *restrict str, char **restrict str_end ); (since C99) Interprets a floating point value in a byte string pointed to by str. Function discards an

Defined in header <string.h> void *memset( void *dest, int ch, size_t count ); (1) errno_t memset_s( void *dest, rsize_t destsz, int ch, rsize_t count ) (2) (since C11) 1) Copies the value ch (after conversion to unsigned char as if by (unsigned char)ch) into each of the first count characters of the object pointed to by dest. The behavior is undefined if access occurs beyond the end of the dest array. The behavior is undefined if dest is a null pointer. 2) Same a

Defined in header <math.h> float expf( float arg ); (1) (since C99) double exp( double arg ); (2) long double expl( long double arg ); (3) (since C99) Defined in header <tgmath.h> #define exp( arg ) (4) (since C99) 1-3) Computes the e (Euler's number, 2.7182818) raised to the given power arg. 4) Type-generic macro: If arg has type long double, expl is called. Otherwise, if arg has integer type or the type double, exp is called. Ot

Defined in header <ctype.h> int isxdigit( int ch ); Checks if the given character is a hexadecimal numeric character (0123456789abcdefABCDEF) or is classified as a hexadecimal character. The behavior is undefined if the value of ch is not representable as unsigned char and is not equal to EOF. Parameters ch - character to classify Return value Non-zero value if the character is an hexadecimal numeric character, zero otherwise. Notes isdigit and isxdigit are

Defined in header <wchar.h> size_t mbsrtowcs( wchar_t* dst, const char** src, size_t len, mbstate_t* ps ) (1) (since C95) errno_t mbsrtowcs_s( size_t *restrict retval, wchar_t *restrict dst, rsize_t dstsz, const char **restrict src, rsize_t len, mbstate_t *restrict ps); (2) (since C11) 1) Converts a null-terminated multibyte character sequence, which begins in the conversion state described by *ps, from the array whose first element is pointed to

Defined in header <stdatomic.h> C atomic_fetch_xor( volatile A* obj, M arg ); (1) (since C11) C atomic_fetch_xor_explicit( volatile A* obj, M arg, memory_order order ); (2) (since C11) Atomically replaces the value pointed by obj with the result of bitwise XOR between the old value of obj and arg, and returns the value obj held previously. The operation is read-modify-write operation. The first version orders memory accesses according to memory_order_seq_cst, the seco

Defined in header <math.h> float ldexpf( float arg, int exp ); (1) (since C99) double ldexp( double arg, int exp ); (2) long double ldexpl( long double arg, int exp ); (3) (since C99) Defined in header <tgmath.h> #define ldexp( arg, exp ) (4) (since C99) 1-3) Multiplies a floating point value arg by the number 2 raised to the exp power. 4) Type-generic macro: If arg has type long double, ldexpl is called. Otherwise, if arg has int

Defined in header <stdlib.h> constraint_handler_t set_constraint_handler_s( constraint_handler_t handler ); (since C11) Configures the handler to be called by all bounds-checked functions on a runtime constraint violation or restores the default handler (if handler is a null pointer). The handler must be a pointer to function of type constraint_handler_t, which is defined as. Defined in header <stdlib.h> typedef void (*constraint_handler_t)( const char *restri

Defined in header <wchar.h> (1) wchar_t *wcscat( wchar_t *dest, const wchar_t *src ); (since C95) (until C99) wchar_t *wcscat(wchar_t *restrict dest, const wchar_t *restrict src); (since C99) errno_t wcscat_s(wchar_t *restrict dest, rsize_t destsz, const wchar_t *restrict src); (2) (since C11) 1) Appends a copy of the wide string pointed to by src to the end of the wide string pointed to by dest. The wide character src[0] replaces the null term