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by **Subhabrata Biswa** » Sat, 19 Dec 1998 04:00:00

Hi,

Do you have to free the struct tm* returned by gmtime() or
localtime() ? In other words, do these calls reuse the same
pointer (or variable) or do they allocate a new pointer for
every call ?

Thanks in advance,

-- Subhabrata Biswas

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by **Aaron Cra** » Sun, 20 Dec 1998 04:00:00

> Do you have to free the struct tm* returned by gmtime() or localtime()?

No. An easy way to remember this is that no standard ISO C library
functions allocate memory (with the obvious exceptions of malloc, realloc,
calloc).

Quote:> In other words, do these calls reuse the same pointer (or variable) or do
> they allocate a new pointer for every call?

It's not your place to know what they do internally, but it's true that most
implementations will use the obvious implementation of having them return a
pointer to a static block of memory. An implementation is at liberty to
play funny games though; for example, it might reasonably return a pointer
to a thread-private block of memory.

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by **Lawrence Kir** » Sun, 20 Dec 1998 04:00:00

Quote:>Hi,

>Do you have to free the struct tm* returned by gmtime() or
>localtime() ?

No, the standard defines that these return a pointer to a static buffer
so attempting to pass these pointers to free() would be a serious error.
Also note that a subsequent call to one of these functions could therefore
overwrite the data from a previous call.

Quote:>In other words, do these calls reuse the same
>pointer (or variable) or do they allocate a new pointer for
>every call ?

No standard C library function except malloc/calloc/realloc allocates
memory that you have to free. Note that strdup() does but it isn't a
standard C library function.

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