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Standard library header <cstdlib>

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< cpp‎ | header
 
 
Standard library headers
Language support
Concepts
<concepts> (C++20)
Diagnostics
<system_error> (C++11)

Memory management
<memory_resource> (C++17)  
Metaprogramming
<type_traits> (C++11)
<ratio> (C++11)
General utilities
<utility>
<tuple> (C++11)
<optional> (C++17)
<variant> (C++17)
<any> (C++17)
<debugging> (C++26)
<expected> (C++23)
<bitset>
<charconv> (C++17)
<format> (C++20)
<bit> (C++20)

Strings
<cuchar> (C++11)

Containers
<flat_set> (C++23)
<span> (C++20)
<mdspan> (C++23)

Iterators
<iterator>
Ranges
<ranges> (C++20)
<generator> (C++23)
Algorithms
Numerics
<cfenv> (C++11)
<complex>
<cmath>
<linalg> (C++26)
<numbers> (C++20)

Time
<chrono> (C++11)
Localization
<codecvt> (C++11/17/26*)
<text_encoding> (C++26)
Input/output
<filesystem> (C++17)
<cstdio>
<cinttypes> (C++11)
<strstream> (C++98/26*)
Regular expressions
<regex> (C++11)
Concurrency support
<stop_token> (C++20)
<thread> (C++11)
<atomic> (C++11)
<rcu> (C++26)
<stdatomic.h> (C++23)
<mutex> (C++11)
<shared_mutex> (C++14)

<condition_variable> (C++11)  
<semaphore> (C++20)
<latch> (C++20)

<barrier> (C++20)
<future> (C++11)
<hazard_pointer> (C++26)

C compatibility
<cstdbool> (C++11/17/20*)  
<ccomplex> (C++11/17/20*)
<ctgmath> (C++11/17/20*)

<cstdalign> (C++11/17/20*)

<ciso646> (until C++20)

 

This header was originally in the C standard library as <stdlib.h>.

This header provides miscellaneous utilities. Symbols defined here are used by several library components.

Contents

Types

structure type, returned by std::div
(typedef) [edit]
structure type, returned by std::ldiv
(typedef) [edit]
(C++11)
structure type, returned by std::lldiv
(typedef) [edit]
unsigned integer type returned by the sizeof operator
(typedef) [edit]

Macro constants

indicates program execution status
(macro constant) [edit]
MB_CUR_MAX
maximum number of bytes in a multibyte character with the current locale
(macro constant) [edit]
implementation-defined null pointer constant
(macro constant) [edit]
maximum possible value generated by std::rand
(macro constant) [edit]

Functions

Process control
causes abnormal program termination (without cleaning up)
(function) [edit]
causes normal program termination with cleaning up
(function) [edit]
causes quick program termination without completely cleaning up
(function) [edit]
(C++11)
causes normal program termination without cleaning up
(function) [edit]
registers a function to be called on std::exit() invocation
(function) [edit]
registers a function to be called on std::quick_exit invocation
(function) [edit]
calls the host environment's command processor
(function) [edit]
access to the list of environment variables
(function) [edit]
Memory management
allocates memory
(function) [edit]
allocates aligned memory
(function) [edit]
allocates and zeroes memory
(function) [edit]
expands or shrinks previously allocated memory block
(function) [edit]
deallocates previously allocated memory
(function) [edit]
Numeric string conversion
converts a byte string to a floating point value
(function) [edit]
converts a byte string to an integer value
(function) [edit]
converts a byte string to an integer value
(function) [edit]
converts a byte string to an unsigned integer value
(function) [edit]
converts a byte string to a floating-point value
(function) [edit]
Wide string manipulation
returns the number of bytes in the next multibyte character
(function) [edit]
converts the next multibyte character to wide character
(function) [edit]
converts a wide character to its multibyte representation
(function) [edit]
converts a narrow multibyte character string to wide string
(function) [edit]
converts a wide string to narrow multibyte character string
(function) [edit]
Miscellaneous algorithms and math
generates a pseudo-random number
(function) [edit]
seeds pseudo-random number generator
(function) [edit]
sorts a range of elements with unspecified type
(function) [edit]
searches an array for an element of unspecified type
(function) [edit]
computes absolute value of an integral value (|x|)
(function) [edit]
computes quotient and remainder of integer division
(function) [edit]

[edit] Synopsis

namespace std {
  using size_t =  /* see description */; // freestanding
  using div_t =   /* see description */; // freestanding
  using ldiv_t =  /* see description */; // freestanding
  using lldiv_t = /* see description */; // freestanding
}
 
#define NULL         /* see description */ // freestanding
#define EXIT_FAILURE /* see description */ // freestanding
#define EXIT_SUCCESS /* see description */ // freestanding
#define RAND_MAX     /* see description */
#define MB_CUR_MAX   /* see description */
 
namespace std {
  // Exposition-only function type aliases
  extern "C" using /* c-atexit-handler */ = void(); // exposition only
  extern "C++" using /* atexit-handler */ = void(); // exposition only
  extern "C" using /* c-compare-pred */ =           // exposition only
    int(const void*, const void*);
  extern "C++" using /* compare-pred */ =           // exposition only
    int(const void*, const void*);
 
  // start and termination
  [[noreturn]] void abort() noexcept;                       // freestanding
  int atexit(/* c-atexit-handler */* func) noexcept;        // freestanding
  int atexit(/* atexit-handler */* func) noexcept;          // freestanding
  int at_quick_exit(/* c-atexit-handler */* func) noexcept; // freestanding
  int at_quick_exit(/* atexit-handler */* func) noexcept;   // freestanding
  [[noreturn]] void exit(int status);                       // freestanding
  [[noreturn]] void _Exit(int status) noexcept;             // freestanding
  [[noreturn]] void quick_exit(int status) noexcept;        // freestanding
 
  char* getenv(const char* name);
  int system(const char* string);
 
  // C library memory allocation
  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);
 
  // multibyte / wide string and character conversion functions
  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 standard library algorithms
  void* bsearch(const void* key, const void* base,  // freestanding
                size_t nmemb, size_t size, /* c-compare-pred */* compar);
  void* bsearch(const void* key, const void* base,  // freestanding
                size_t nmemb, size_t size, /* compare-pred */* compar);
  void qsort(void* base, size_t nmemb, size_t size, // freestanding
             /* c-compare-pred */* compar);
  void qsort(void* base, size_t nmemb, size_t size, // freestanding
             /* compare-pred */* compar);
 
  // low-quality random number generation
  int rand();
  void srand(unsigned int seed);
 
  // absolute values
  constexpr int abs(int j);                       // freestanding
  constexpr long int abs(long int j);             // freestanding
  constexpr long long int abs(long long int j);   // freestanding
  constexpr /* floating-point-type */
    abs(/* floating-point-type */ j);             // freestanding-deleted
 
  constexpr long int labs(long int j);            // freestanding
  constexpr long long int llabs(long long int j); // freestanding
 
  constexpr div_t div(int numer, int denom);                         // freestanding
  constexpr ldiv_t div(long int numer, long int denom);              // freestanding
  constexpr lldiv_t div(long long int numer, long long int denom);   // freestanding
  constexpr ldiv_t ldiv(long int numer, long int denom);             // freestanding
  constexpr lldiv_t lldiv(long long int numer, long long int denom); // freestanding
}

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 286 C++98 the definition of size_t was not provided in <cstdlib> provided

[edit] See also