Does memory for localtime need to be deallocated?

Question

void log(){
    time_t current = time(0);
    tm *ptm = localtime(&current);
        stuf...
}

Just want to be sure - do i need to release tm pointer allocated memory at the end of the method?

possible duplicate of [How is the result struct of localtime allocated in C?](http://stackoverflow.com/questions/8694365/how-is-the-result-struct-of-localtime-allocated-in-c) — user, Oct 19 '14 at 08:30
Also see [How to resolve dyld and localtime leaks when profiling a project?](http://stackoverflow.com/q/10105181) — jww, Oct 02 '15 at 16:25

score 27 · Accepted Answer · answered Aug 31 '12 at 09:16

27

No you should not deallocate it,the structure is statically allocated.

Check the documentation:

Return value
pointer to a static internal std::tm object on success, or NULL otherwise. The structure may be shared between std::gmtime, std::localtime, and std::ctime, and may be overwritten on each invocation.

answered Aug 31 '12 at 09:16

Alok Save

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what do you mean by statically allocated? dosnt it allocated on the heap by the localtime implementation? – Avihai Marchiano Aug 31 '12 at 09:18
@user1495181: Added reference for you. – Alok Save Aug 31 '12 at 09:20
OH thanks , i missed it, and now i know that localtime is not thread safe.:( – Avihai Marchiano Aug 31 '12 at 09:25
2

@user1495181: Posix has `localtime_r`, which is thread-safe. You pass in a pointer to the `struct tm` result. But it's not in standard C++. It *is* in the latest version of C (C11), as `localtime_s`. – Steve Jessop Aug 31 '12 at 09:26
@user1495181 It **could** be thread safe. E.g. in MSVC++ this structure is maintained per each thread. Check your compiler docs. – Rost Aug 31 '12 at 09:28

score 8 · Answer 2 · answered Aug 31 '12 at 09:23

No, you shouldn't. This structure is statically allocated and shared by the functions gmtime and localtime. Each time either one of these functions is called the content of this structure is overwritten.

So be careful with results - e.g. copy them immediately and don't store the pointer.

Does memory for localtime need to be deallocated?

2 Answers2

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