Introduction to C++ header files — <cstdlib> header files

Introduction to C++ header files— <cstdlib>header files

<cstdlib>head File

Introduction

The C++ Standard Library headers <cstdlib>are the most widely used library headers by C++ programmers. It defines a set of functions and macros to enable efficient and performant standardized C++ code across teams and platforms.

C++ is a popular programming language, and the original reason for its rise is that it can be compatible with the C language. The C language was and still is a popular, mature programming language. Compatibility means that it is easier for programmers to adapt to the language, and more importantly, C++ developers can also leverage existing C code.

Programmers don't need to rebuild everything from the core functions, and can reuse mature code blocks as they move to C++ at a reasonable pace. Specifically, they can take advantage of the C language standard library header files<stdlib.h>

Currently, the C++ cstdlib is <stdlib.h>an enhanced version of the original C++.

namespaces and macros

namespace std {
    
    
    using size_t = see definition;
    using div_t = see definition;
    using ldiv_t = see definition;
    using lldiv_t = see definition;
}

#define NULL
#define EXIT_FAILURE
#define EXIT_SUCCESS
#define RAND_MAX
#define MB_CUR_MAX

macro constant

macro constant	use
EXIT_SUCCESS、EXIT_FAILURE	Indicates the execution status of program execution
MB_CUR_MAX	The maximum number of bytes for a multibyte character in the current locale
NULL	implementation-defined null pointer constant
RAND_MAX	std::randThe largest possible value generated

type

type	use
div_t	Structure type, std::divfunction return value
ldiv_t	Structure type, std::ldivfunction return value
lldiv_t	Structure type, std::lldivfunction return value
size_t	sizeofthe unsigned integer type returned by the operator

function

process control

function	use
abort	Causes an abnormal program termination (without cleanup)
exit	Causes normal program termination and cleanup
quick_exit	Causes quick program termination without complete cleanup
_Exit	Causes normal program termination without cleanup
atexit	registers std::exit()a function that will be called when
at_quick_exit	Register a function that will be called when quick_exit is called
system	Invoke the host environment's command handler
getenv	Access the list of environment variables

memory management

function	use
malloc	Allocate memory
aligned_alloc	allocate aligned memory
calloc	Allocate and zero memory
realloc	Expand a previously allocated block of memory
free	Deallocates previously allocated memory

Numeric String Conversion

function	use
atof	converts a byte string to a floating point value
atoi、atol、atoll	Converts a byte string to an integer value
strtol、strtoll	Converts a byte string to an integer value
strtoul、strtoull	converts a byte string to an unsigned integer value
strtof、strtod、strtold	converts a byte string to a floating point value

Wide String Operations

function	use
mblen	Returns the number of bytes in the next multibyte character
mbtowc	Convert the next multibyte character to a wide character
wctomb	converts a wide character to its multibyte representation
mbstowcs	converts a narrow multibyte string to a wide string
wcstombs	converts a wide string to a narrow multibyte string

Miscellaneous Algorithms and Mathematics

function	use
rand	生成伪随机数
srand	初始化伪随机数生成器
qsort	对未指定类型的元素的一个范围进行排序
bsearch	在未指定类型的数组中搜索元素
abs、labs、llabs	计算整数值的绝对值
div、ldiv、lldiv	计算整数除法的商和余数

概要

namespace std {
    
    
  using size_t = ;
  using div_t = ;
  using ldiv_t = ;
  using lldiv_t = ;
}
#define NULL 
#define EXIT_FAILURE 
#define EXIT_SUCCESS 
#define RAND_MAX 
#define MB_CUR_MAX 
namespace std {
    
    
  extern "C" using /*c-atexit-handler*/ = void(); 
  extern "C++" using /*atexit-handler*/ = void(); 
  extern "C" using /*c-compare-pred*/ = int(const void* , const void*); 
  extern "C++" using /*compare-pred*/ = int(const void* , const void*); 
  // 启动与终止
  [[noreturn]] void abort() noexcept;
  int atexit(/*c-atexit-handler*/ * func) noexcept;
  int atexit(/*atexit-handler*/ * func) noexcept;
  int at_quick_exit(/*c-atexit-handler*/ * func) noexcept;
  int at_quick_exit(/*atexit-handler*/ * func) noexcept;
  [[noreturn]] void exit(int status);
  [[noreturn]] void _Exit(int status) noexcept;
  [[noreturn]] void quick_exit(int status) noexcept;
  char* getenv(const char* name);
  int system(const char* string);
  // C 标准库内存分配
  void* aligned_alloc(size_t alignment, size_t size);
  void* calloc(size_t nmemb, size_t size);
  void free(void* ptr);
  void* malloc(size_t size);
  void* realloc(void* ptr, size_t size);
  double atof(const char* nptr);
  int atoi(const char* nptr);
  long int atol(const char* nptr);
  long long int atoll(const char* nptr);
  double strtod(const char* nptr, char** endptr);
  float strtof(const char* nptr, char** endptr);
  long double strtold(const char* nptr, char** endptr);
  long int strtol(const char* nptr, char** endptr, int base);
  long long int strtoll(const char* nptr, char** endptr, int base);
  unsigned long int strtoul(const char* nptr, char** endptr, int base);
  unsigned long long int strtoull(const char* nptr, char** endptr, int base);
  // 多字节/宽字符串及字符转换函数
  int mblen(const char* s, size_t n);
  int mbtowc(wchar_t* pwc, const char* s, size_t n);
  int wctomb(char* s, wchar_t wchar);
  size_t mbstowcs(wchar_t* pwcs, const char* s, size_t n);
  size_t wcstombs(char* s, const wchar_t* pwcs, size_t n);
  // C 标准库算法
  void* bsearch(const void* key, const void* base,
                size_t nmemb, size_t size, /*c-compare-pred*/ * compar);
  void* bsearch(const void* key, const void* base,
                size_t nmemb, size_t size, /*compare-pred*/ * compar);
  void qsort(void* base, size_t nmemb, size_t size, /*c-compare-pred*/ * compar);
  void qsort(void* base, size_t nmemb, size_t size, /*compare-pred*/ * compar);
  // 低质量随机数生成
  int rand();
  void srand(unsigned int seed);
  // 绝对值
  int abs(int j);
  long int abs(long int j);
  long long int abs(long long int j);
  float abs(float j);
  double abs(double j);
  long double abs(long double j);
  long int labs(long int j);
  long long int llabs(long long int j);
  div_t div(int numer, int denom);
  ldiv_t div(long int numer, long int denom);
  lldiv_t div(long long int numer, long long int denom); 
  ldiv_t ldiv(long int numer, long int denom);
  lldiv_t lldiv(long long int numer, long long int denom);
}

参考

• https://c-cpp.com/cpp/utility/program.html

• https://zhuanlan.zhihu.com/p/447992440

• https://c-cpp.com/cpp/numeric/random.html

• https://learn.microsoft.com/zh-cn/cpp/standard-library/cstdlib?view=msvc-170

• https://baike.baidu.com/item/cstdlib/5519425?fr=ge_ala