Bug#318317: libc6: Numerous (49) memory leaks in gethostbyname, as reported by mudflap

[GOMBAS Gabor <gombasg@sztaki.hu>]

On Thu, Jul 14, 2005 at 10:17:32PM +0300, Vesselin Peev wrote:

> Could you please elucidate what is this programming pattern that causes the 
> leaks, if it is possible to do with a programming snippet? I find it very 
> strange that a well-working program will have leaks that are considered 
> necessary because of a quite common usage pattern. Isn't there a better, 
> more perfect way? 

Very simple: gethostbyname() returns a "struct hostent *" for which the
C library has to allocate some internal memory. However,
POSIX/SUS/etc. does not define any API to tell the C library that the
returned pointer is no longer needed, so the allocated memory cannot be
freed by the C library until the next call to gethostbyname().

Solution: do not use the gethostby* functions. Use get{addr|name}info()
instead, they do not have this API problem (and have other advantages
as well).

Gabor

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     MTA SZTAKI Computer and Automation Research Institute
                Hungarian Academy of Sciences
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