xapian core missing link to math on MSYS2

[Mario Emmenlauer]

Dear Olly,

On 17.03.2017 11:31, Olly Betts wrote:
> On Fri, Mar 17, 2017 at 11:04:43AM +0100, Mario Emmenlauer wrote:
>> thanks a lot for the pointer! I've fetched the patch you mention but
>> actually it seems this is already included in the 1.4.3 release, is
>> that possible?
> 
> Oh yes it is.  Sorry, it seems this got missed from the NEWS file, and
> so I assumed it wasn't in a release yet.
> 
>> Also it did not solve the problem, I still get references
>> to exp10. I've checked with nm and omenquire.o has undefined references
>> to log10 and exp10.
> 
> log10() is C99 and POSIX, so that should be OK.
> 
>> I went further and replaced exp10 in omenquire.cc
>> with __builtin_exp10, but still the same undefined references. I do not
>> know what kind of black magic this is...
> 
> I can confirm this with a simple test program and a cross-compiler:
> 
> $ cat exp10.cc
> int main(int argc, char **) { return (int)__builtin_exp10((double)argc); }
> $ i686-w64-mingw32-g++ -O2 -Wall -W exp10.cc 
> /tmp/cc3O99Ry.o:exp10.cc:(.text.startup+0x15): undefined reference to `exp10'
> collect2: error: ld returned 1 exit status
> 
> So GCC thinks it can call exp10() to implement __builtin_exp10()!  Not
> really sure how to sanely handle that.
> 
> At least for a workaround, I'd suggest pow(10.0, x) (unless GCC tries to
> convert that to exp10(x) too).

Great, that works and fixes the problem. I've created a PR with the
latest xapian (and your fix) for inclusion in MSYS2 here:
https://github.com/Alexpux/MINGW-packages/pull/2316

Cheers,

    Mario Emmenlauer