libgo/runtime/go-matherr.c

   1 /* go-matherr.c -- a Go version of the matherr function.
   2
   3    Copyright 2012 The Go Authors. All rights reserved.
   4    Use of this source code is governed by a BSD-style
   5    license that can be found in the LICENSE file.  */
   6
   7 /* The gccgo version of the math library calls libc functions.  On
   8    some systems, such as Solaris, those functions will call matherr on
   9    exceptional conditions.  This is a version of matherr appropriate
  10    for Go, one which returns the values that the Go math library
  11    expects.  This is fine for pure Go programs.  For mixed Go and C
  12    programs this will be problematic if the C programs themselves use
  13    matherr.  Normally the C version of matherr will override this, and
  14    the Go code will just have to cope.  If this turns out to be too
  15    problematic we can change to run pure Go code in the math library
  16    on systems that use matherr.  */
  17
  18 #include <math.h>
  19 #include <stdint.h>
  20
  21 #include "config.h"
  22
  23 #if defined(HAVE_MATHERR) && defined(HAVE_STRUCT_EXCEPTION)
  24
  25 #define PI 3.14159265358979323846264338327950288419716939937510582097494459
  26
  27 int
  28 matherr (struct exception* e)
  29 {
  30   const char *n;
  31
  32   if (e->type != DOMAIN)
  33     return 0;
  34
  35   n = e->name;
  36   if (__builtin_strcmp (n, "acos") == 0
  37       || __builtin_strcmp (n, "asin") == 0)
  38     e->retval = __builtin_nan ("");
  39   else if (__builtin_strcmp (n, "atan2") == 0)
  40     {
  41       if (e->arg1 == 0 && e->arg2 == 0)
  42         {
  43           double nz;
  44
  45           nz = -0.0;
  46           if (__builtin_memcmp (&e->arg2, &nz, sizeof (double)) != 0)
  47             e->retval = e->arg1;
  48           else
  49             e->retval = copysign (PI, e->arg1);
  50         }
  51       else
  52         return 0;
  53     }
  54   else if (__builtin_strcmp (n, "log") == 0
  55            || __builtin_strcmp (n, "log10") == 0)
  56     e->retval = __builtin_nan ("");
  57   else if (__builtin_strcmp (n, "pow") == 0)
  58     {
  59       if (e->arg1 < 0)
  60         e->retval = __builtin_nan ("");
  61       else if (e->arg1 == 0 && e->arg2 == 0)
  62         e->retval = 1.0;
  63       else if (e->arg1 == 0 && e->arg2 < 0)
  64         {
  65           double i;
  66
  67           if (modf (e->arg2, &i) == 0 && ((int64_t) i & 1) == 1)
  68             e->retval = copysign (__builtin_inf (), e->arg1);
  69           else
  70             e->retval = __builtin_inf ();
  71         }
  72       else
  73         return 0;
  74     }
  75   else if (__builtin_strcmp (n, "sqrt") == 0)
  76     {
  77       if (e->arg1 < 0)
  78         e->retval = __builtin_nan ("");
  79       else
  80         return 0;
  81     }
  82   else
  83     return 0;
  84
  85   return 1;
  86 }
  87
  88 #endif