Re: long double and GLIBCPP_CHECK_MATH_SUPPORT

[Benjamin Kosnik <bkoz at redhat dot com>]

David. 

Let's back up a bit. 

I put in these checks for long double as a quick hack to work around
powerpc build issues. In particular, the following (legal) code would
not compile:

extern "C" {
  extern double cos ( double __x); 
  extern float cosf ( float __x); 
}


namespace std {
  inline float cos(float __x) { return ::cosf(__x); }
  inline double cos(double __x) { return ::cos(__x); }
}

void test01()
{
  long double d = 1111.111;
  std::cos(d);
}


This code has to compile. The current sources give an ambiguity here,
which is not going to work. 

If you look in 26/numerics, you can see that cmath *requires* long
double overloads for math types, even if the underlying "C" math
library does not support them. I think the best solution is to do
something like:

#if _GLIBCPP_HAVE___BUILTIN_SINL
  inline long double 
  sin(long double __x) { return __builtin_sinl(__x); }
#elif _GLIBCPP_HAVE_SINL
  inline long double 
  sin(long double __x) { return ::sinl(__x); }
#else
  inline long double 
  sin(long double __x) { return ::sin(static_cast<double>(__x)); }
#endif

Which incidentally matches the float overloads. It allows the
compilation of the code above, and I've tested this on both powerpc
and x86. Granted, the results are sketchy, but I believe if user code
runs into problems here, the resulting problems will be easier to find
(and less aggravating) than a compile time error on legal code.

I'd like to remove this flag, the macro, and the support that went in
with it. I suppose this is a change you'll object to.

From what I understand, you are trying to optimize the configure
process, correct? Can you clarify your intent please?

-benjamin


2000-10-26  Benjamin Kosnik  <bkoz@redhat.com>

	* acinclude.m4 (GLIBCPP_ENABLE_LONG_DOUBLE): Remove.
	* aclocal.m4: Regenerate.
	* configure.in: Remove GLIBCPP_ENABLE_LONG_DOUBLE.
	* configure: Regenerate.
	* docs/configopts.html: Remove.
	* src/complexl.cc: Revert.
	* config.h.in: Remove.
	* include/c_std/bits/std_cmath.h: Remove guards based on
	_GLIBCPP_USE_LONG_DOUBLE.
	* include/c/bits/std_cmath.h: Same. Format. Match c_std behavior
	with respect to long double signatures.