231 lines
9.4 KiB
Markdown
231 lines
9.4 KiB
Markdown
[support.start.term]
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# 17 Language support library [[support]](./#support)
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## 17.5 Startup and termination [support.start.term]
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2109)
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[*Note [1](#note-1)*:
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The header [<cstdlib>](cstdlib.syn#header:%3ccstdlib%3e "17.2.2 Header <cstdlib> synopsis [cstdlib.syn]") declares the functions described in this subclause[.](#1.sentence-1)
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â *end note*]
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[ð](#lib:_Exit)
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`[[noreturn]] void _Exit(int status) noexcept;
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`
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2121)
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*Effects*: This function has the semantics specified in the C standard library[.](#2.sentence-1)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2125)
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*Remarks*: The program is terminated without executing destructors for objects with automatic,
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thread, or static storage duration and without calling functions passed toatexit() ([[basic.start.term]](basic.start.term "6.10.3.4 Termination"))[.](#3.sentence-1)
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The function _Exit is [signal-safe](support.signal#def:evaluation,signal-safe "17.14.5 Signal handlers [support.signal]")[.](#3.sentence-2)
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[ð](#lib:abort)
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`[[noreturn]] void abort() noexcept;
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`
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2140)
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*Effects*: This function has the semantics specified in the C standard library[.](#4.sentence-1)
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[5](#5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2144)
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*Remarks*: The program is terminated without executing destructors for objects of
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automatic, thread, or static storage
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duration and without calling functions passed toatexit() ([[basic.start.term]](basic.start.term "6.10.3.4 Termination"))[.](#5.sentence-1)
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The function abort is [signal-safe](support.signal#def:evaluation,signal-safe "17.14.5 Signal handlers [support.signal]")[.](#5.sentence-2)
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[ð](#lib:atexit)
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`int atexit(c-atexit-handler* f) noexcept;
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int atexit(atexit-handler* f) noexcept;
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`
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[6](#6)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2161)
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*Effects*: Theatexit() functions register the function pointed to by f to be called without arguments at normal program termination[.](#6.sentence-1)
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It is unspecified whether a call to atexit() that does not[happen before](intro.multithread#def:happens_before "6.10.2 Multi-threaded executions and data races [intro.multithread]") a call to exit() will succeed[.](#6.sentence-2)
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[*Note [2](#note-2)*:
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The atexit() functions do not introduce a data
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race ([[res.on.data.races]](res.on.data.races "16.4.6.10 Data race avoidance"))[.](#6.sentence-3)
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â *end note*]
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[7](#7)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2175)
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*Implementation limits*: The implementation shall support the registration of at least 32 functions[.](#7.sentence-1)
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[8](#8)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2179)
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*Returns*: Theatexit() function returns zero if the registration succeeds,
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nonzero if it fails[.](#8.sentence-1)
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[ð](#lib:exit)
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`[[noreturn]] void exit(int status);
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`
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[9](#9)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2193)
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*Effects*:
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- [(9.1)](#9.1)
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First, objects with thread storage duration and associated with the current thread
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are destroyed[.](#9.1.sentence-1)
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Next, objects with static storage duration are destroyed
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and functions registered by callingatexit are called[.](#9.1.sentence-2)[186](#footnote-186 "A function is called for every time it is registered.")
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See [[basic.start.term]](basic.start.term "6.10.3.4 Termination") for the order of destructions and calls[.](#9.1.sentence-3)
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(Objects with automatic storage duration are not destroyed as a result of callingexit()[.](#9.1.sentence-4))[187](#footnote-187 "Objects with automatic storage duration are all destroyed in a program whose main function ([basic.start.main]) contains no objects with automatic storage duration and executes the call to exit(). Control can be transferred directly to such a main function by throwing an exception that is caught in main.")
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If a registered function invoked by exit exits via an exception,
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the function std::terminate is invoked ([[except.terminate]](except.terminate "14.6.2 The std::terminate function"))[.](#9.1.sentence-5)
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- [(9.2)](#9.2)
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Next, all open C streams (as mediated by the function
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signatures declared in [<cstdio>](cstdio.syn#header:%3ccstdio%3e "31.13.1 Header <cstdio> synopsis [cstdio.syn]"))
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with unwritten buffered data are flushed, all open C
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streams are closed, and all files created by callingtmpfile() are removed[.](#9.2.sentence-1)
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- [(9.3)](#9.3)
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Finally, control is returned to the host environment[.](#9.3.sentence-1)
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If status is zero orEXIT_SUCCESS,
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an implementation-defined
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form of the status[*successful termination*](#def:successful_termination) is returned[.](#9.3.sentence-2)
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If status isEXIT_FAILURE,
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an implementation-defined form of the status[*unsuccessful termination*](#def:unsuccessful_termination) is returned[.](#9.3.sentence-3)
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Otherwise the status returned is implementation-defined[.](#9.3.sentence-4)[188](#footnote-188 "The macros EXIT_FAILURE and EXIT_SUCCESS are defined in <cstdlib>.")
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[ð](#lib:at_quick_exit)
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`int at_quick_exit(c-atexit-handler* f) noexcept;
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int at_quick_exit(atexit-handler* f) noexcept;
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`
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[10](#10)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2258)
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*Effects*: The at_quick_exit() functions register the function pointed to by f to be called without arguments when quick_exit is called[.](#10.sentence-1)
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It is unspecified whether a call to at_quick_exit() that does not[happen before](intro.multithread#def:happens_before "6.10.2 Multi-threaded executions and data races [intro.multithread]") all calls to quick_exit will succeed[.](#10.sentence-2)
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[*Note [3](#note-3)*:
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Theat_quick_exit() functions do not introduce a
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data race ([[res.on.data.races]](res.on.data.races "16.4.6.10 Data race avoidance"))[.](#10.sentence-3)
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â *end note*]
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[*Note [4](#note-4)*:
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The order of registration could be indeterminate if at_quick_exit was called from more
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than one thread[.](#10.sentence-4)
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â *end note*]
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[*Note [5](#note-5)*:
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Theat_quick_exit registrations are distinct from the atexit registrations,
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and applications might need to call both registration functions with the same argument[.](#10.sentence-5)
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â *end note*]
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[11](#11)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2280)
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*Implementation limits*: The implementation shall support the registration of at least 32 functions[.](#11.sentence-1)
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[12](#12)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2284)
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*Returns*: Zero if the registration succeeds, nonzero if it fails[.](#12.sentence-1)
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[ð](#lib:quick_exit)
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`[[noreturn]] void quick_exit(int status) noexcept;
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`
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[13](#13)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2295)
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*Effects*: Functions registered by calls to at_quick_exit are called in the
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reverse order of their registration, except that a function shall be called after any
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previously registered functions that had already been called at the time it was
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registered[.](#13.sentence-1)
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Objects shall not be destroyed as a result of calling quick_exit[.](#13.sentence-2)
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If a registered function invoked by quick_exit exits via an exception,
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the function std::terminate is invoked ([[except.terminate]](except.terminate "14.6.2 The std::terminate function"))[.](#13.sentence-3)
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[*Note [6](#note-6)*:
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A function registered via at_quick_exit is invoked by the thread that calls quick_exit,
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which can be a different thread
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than the one that registered it, so registered functions cannot rely on the identity
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of objects with thread storage duration[.](#13.sentence-4)
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â *end note*]
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After calling registered functions, quick_exit shall call _Exit(status)[.](#13.sentence-5)
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[14](#14)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L2313)
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*Remarks*: The function quick_exit is [signal-safe](support.signal#def:evaluation,signal-safe "17.14.5 Signal handlers [support.signal]") when the functions registered with at_quick_exit are[.](#14.sentence-1)
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See also: ISO/IEC 9899:2024, 7.24.4
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[186)](#footnote-186)[186)](#footnoteref-186)
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A function is called for every time it is registered[.](#footnote-186.sentence-1)
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[187)](#footnote-187)[187)](#footnoteref-187)
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Objects with automatic storage duration are all destroyed in a program whosemain function ([[basic.start.main]](basic.start.main "6.10.3.1 main function"))
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contains no objects with automatic storage duration and executes the call toexit()[.](#footnote-187.sentence-1)
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Control can be transferred directly to such amain function
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by throwing an exception that is caught inmain[.](#footnote-187.sentence-2)
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[188)](#footnote-188)[188)](#footnoteref-188)
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The macros EXIT_FAILURE and EXIT_SUCCESS are defined in [<cstdlib>](cstdlib.syn#header:%3ccstdlib%3e "17.2.2 Header <cstdlib> synopsis [cstdlib.syn]")[.](#footnote-188.sentence-1)
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