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


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.)  All my Newlib targets are ELF.)  An alternative implementation could be macro definitions in math.h.
Craig


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