[squid-dev] [PATCH] Fix libatomic detection

[Amos Jeffries]

On 28/12/2015 10:25 p.m., Kinkie wrote:
> Hi,
> 
> On Mon, Dec 28, 2015 at 1:32 AM, Amos Jeffries wrote:
>> On 24/12/2015 11:32 a.m., Kinkie wrote:
>>> Hi,
>>>   libatomic detection is currently broken in configure.ac; it will
>>> define -latomic even in case where it wouldn't be required (e.g.
>>> because it's already provided by the compiler).
>>> The attached patch fixes the broken case. Unfortunately I don't know a
>>> system where this library is required, I'm convinced there's room for
>>> further simplification.
>>
>> It was for Clang builds IIRC. At least 3.5 needs it added.
>>
>> Does this work instead for shorter code?
>>   AC_SEARCH_LIBS([__atomic_load_8],[atomic],[
>>     ATOMICLIB="$ac_cv_search___atomic_load_8"
>>   ],[])
> 
> unfortunately not, as the result could be "none required" or "no",
> too. The former is actually the error case which bought me to the
> topic.
> Documentation states that if a library is needed it should get
> automatically added to LIBS though.

"Unless the 3rd and 4th parameters are specified". So it will be
automatically added under your patch, but not under the existing/older code.

Which was an intentional omission from LIBS to avoid build warnings on
some distros about unnecessary dependencies being linked in (such as
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=770928>). Since most
of the helper binaries do not use atomics (yet, though we could thread
them in future) the -latomic addition is only needed by squid_LDADD not
the generic LIBS / LDADD.

Amos