Patch: bug fix for PR18218

[Matt Calabrese]

This still technically behaves differently from what the standard
specifies. One example is that since the parameters in question are
taken by value, the argument that is convertible to the arithmetic
type must be movable and/or copyable (depending on context), otherwise
the function won't be able to be called (and in the case where the
type is copyable or movable, you are intruding a [potentially
non-trivial] copy/move operation that shouldn't be happening). The
actual specified version would just work. The parameter could be taken
by r-value reference and things could be slightly adjusted to have
this type of case work, but there will still be other subtle problems,
such as the signature change.

Ultimately, I think it's best to just follow the standard exactly to
avoid subtleties like this. It might be best to just stamp out the
overloads with the preprocessor either through individual macro
invocations or via an inclusion trick, probably preferring the latter
over the former. To elaborate on that, you could include the same file
internally, multiple times, but each time with a different arithmetic
type specified as the redefinition of a macro used by the
implementation:

#define __CURRENT_CMATH_TYPE float
#include <some_underlying_implementation_file>
#undef __CURRENT_CMATH_TYPE
#define __CURRENT_CMATH_TYPE double
#include <some_underlying_implementation_file>
// etc.

It's hairy, but at least you're guaranteed to not stray from specified
behavior and you're still removing redundancy.

On Thu, Dec 19, 2013 at 9:26 AM, Marshall Clow <mclow.lists at gmail.com> wrote:
> http://llvm.org/bugs/show_bug.cgi?id=18218
>
> This turned out not to be a problem with isnan, but rather a pervasive pattern encompassing all of the functions in <cmath>
>
> The patch is very large, but is really just the same bug fix applied to:
>         abs, acos asin, atan, atan2, ceil, cos, cosh, exp, fabs, floor, fmod, frexp, ldexp, log, log10, modf, pow, sin, sinh, sqrt, tan, tanh, signbit, fpclassify, isfinite, isinf, isnan, isnormal, isgreater, isgreaterequal, isless, islessequal, islessgreater, isunordered, acosh, asinh, atanh, cbrt, copysign, erf, erfc, exp2, expm1, fdim, fma, fmax, fmin, hypot, ilogb, lgamma, llrint, llround, log1p, log2, logb, lrint, lround, nearbyint, nextafter, nexttoward, remainder, remquo, rint, round, scalbln, scalbn, tgamma, trunc
>
> -- Marshall
>
> Marshall Clow     Idio Software   <mailto:mclow.lists at gmail.com>
>
> A.D. 1517: Martin Luther nails his 95 Theses to the church door and is promptly moderated down to (-1, Flamebait).
>         -- Yu Suzuki
>
>
> _______________________________________________
> cfe-commits mailing list
> cfe-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>



-- 
-Matt Calabrese