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Re: [Xen-devel] [PATCH] autoconf: add missing compression checks for libxc

>>> On 06.03.12 at 18:27, Roger Pau MonnÃ<roger.pau@xxxxxxxxxxxxx> wrote:
> 2012/3/6 Jan Beulich <JBeulich@xxxxxxxx>:
>>>>> On 06.03.12 at 16:01, Roger Pau MonnÃ<roger.pau@xxxxxxxxxxxxx> wrote:
>>> 2012/3/6 Jan Beulich <JBeulich@xxxxxxxx>:
>>>> ... are you certain that checking for these symbols in the respective
>>>> libraries suffices? The old check really was verifying corresponding
>>>> header files' presence.
>>> I think it's best to do it this way, what this tests do is try to
>>> compile a sample program that uses the library, which is much more
>>> closer to the reality than just checking for a header existence. In a
>>> strange case you might have the header files, but maybe the library is
>>> broken, so we can not use it. What I can do if you want is check for
>>> the header files also, something like this?
>> Hmm, no - I was rather thinking of a real usability test (which implies
>> existence), i.e. include the header in the test source snippet. This is
>> what really matches reality.
> The last patch does this more or less, it's just that not on the same
> test. If headers are found and are usable then we perform a library
> check, basically it does the same as the previous test found in
> tools/libxc/Makefile but also checks that the library is usable for
> linking.

Not really - this is an example of what is being tried to get compiled
and linked:

#ifdef __cplusplus
extern "C"
char BZ2_bzDecompressInit ();
main ()
return BZ2_bzDecompressInit ();
  return 0;

- no inclusion of the header in question, using a bogus prototype


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