Define HAVE_ for math long double functions declared in vxworks headers

[Alexandre Oliva]

On Jan 22, 2020, Andreas Schwab <schwab@suse.de> wrote:

> On Dez 25 2019, Alexandre Oliva wrote:
>> +dnl # Different versions and execution modes implement different
>> +dnl # subsets of these functions.  Instead of hard-coding, test for C
>> +dnl # declarations in headers.  The C primitives could be defined as
>> +dnl # macros, in which case the tests might fail, and we might have to
>> +dnl # switch to more elaborate tests.
>> +    GLIBCXX_CHECK_MATH_DECLS([
>> +      acosl asinl atan2l atanl ceill cosl coshl expl fabsl floorl fmodl
>> +      frexpl ldexpl log10l logl modfl powl sinl sinhl sqrtl tanl tanhl])

> Why can't you use AC_CHECK_DECLS?

IIRC it doesn't #undef, for one, but that's only relevant now.

I can't really recall whether using it even occurred to me, but a good
reason not to use it is that it defines HAVE_FUNCTION_DECL rather than
setting glibcxx_cv_func_$1_use={yes,no} and (through AC_CHECK_FUNCS)
HAVE_$1, like the preexisting macros in linkage.m4 we're substituting
for did before.

We could probably use AC_CHECK_DECL underneath, placing the #undef in
the INCLUDES argument.  Indeed, it looks like the GLIBCXX_CHECK_*_DECL_?
macros in linkage.m4 could use AC_CHECK_DECL as well.

Does anyone know of any reason for them not to use AC_CHECK_DECL
instead of open-coding the tests?


And then, shouldn't they also #undef the functions they're testing for?
Or should neither?  It doesn't feel right to add the #undef to the new
but otherwise identical compile test, just because it skips the link
test.

-- 
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