[PATCH 3/4] In _IEEE_LIBM mode, use weak symbols instead of wrapper funcs

[Craig Howland]

On 08/27/2018 02:32 PM, keithp@keithp.com wrote:
> From: Keith Packard <keithp@keithp.com>
>
> When the math library is compiled to just use bare IEEE_LIBM mode, many
> public functions are just wrappers around the __ieee754 version.
> Eliminate the extra function by creating a weak alias symbol for the
> public name directly from the ieee754 name.
>
> Signed-off-by: Keith Packard <keithp@keithp.com>
> ---
>   newlib/libm/math/e_acos.c       |  5 +++++
>   ...
>   86 files changed, 360 insertions(+), 197 deletions(-)
>
> diff --git a/newlib/libm/math/e_acos.c b/newlib/libm/math/e_acos.c
> index 319b1d56f..25509c0f0 100644
> --- a/newlib/libm/math/e_acos.c
> +++ b/newlib/libm/math/e_acos.c
> @@ -59,6 +59,11 @@ qS2 =  2.02094576023350569471e+00, /* 0x40002AE5, 0x9C598AC8 */
>   qS3 = -6.88283971605453293030e-01, /* 0xBFE6066C, 0x1B8D0159 */
>   qS4 =  7.70381505559019352791e-02; /* 0x3FB3B8C5, 0xB12E9282 */
>   
> +#ifdef _IEEE_LIBM
> +double acos(double x)
> +	__attribute__((weak, alias("__ieee754_acos")));
> +#endif
> +
>   #ifdef __STDC__
>   	double __ieee754_acos(double x)
>   #else
> ...
While this is a nice idea, it is a problem for targets which don't support weak 
aliases (i.e. those without proper object file support for them).  (Does anyone 
know for certain if this is a real problem instead of just a theoretical one?  
(I'd guess so.)Â  All my Newlib targets are ELF.)Â  An alternative implementation 
could be macro definitions in math.h.
Craig