+/* go-matherr.c -- a Go version of the matherr function.
+
+ Copyright 2012 The Go Authors. All rights reserved.
+ Use of this source code is governed by a BSD-style
+ license that can be found in the LICENSE file. */
+
+/* The gccgo version of the math library calls libc functions. On
+ some systems, such as Solaris, those functions will call matherr on
+ exceptional conditions. This is a version of matherr appropriate
+ for Go, one which returns the values that the Go math library
+ expects. This is fine for pure Go programs. For mixed Go and C
+ programs this will be problematic if the C programs themselves use
+ matherr. Normally the C version of matherr will override this, and
+ the Go code will just have to cope. If this turns out to be too
+ problematic we can change to run pure Go code in the math library
+ on systems that use matherr. */
+
+#include <math.h>
+#include <stdint.h>
+
+#include "config.h"
+
+#if defined(HAVE_MATHERR) && defined(HAVE_STRUCT_EXCEPTION)
+
+#define PI 3.14159265358979323846264338327950288419716939937510582097494459
+
+int
+matherr (struct exception* e)
+{
+ const char *n;
+
+ if (e->type != DOMAIN)
+ return 0;
+
+ n = e->name;
+ if (__builtin_strcmp (n, "acos") == 0
+ || __builtin_strcmp (n, "asin") == 0)
+ e->retval = NAN;
+ else if (__builtin_strcmp (n, "atan2") == 0)
+ {
+ if (e->arg1 == 0 && e->arg2 == 0)
+ {
+ double nz;
+
+ nz = -0.0;
+ if (__builtin_memcmp (&e->arg2, &nz, sizeof (double)) != 0)
+ e->retval = e->arg1;
+ else
+ e->retval = copysign (PI, e->arg1);
+ }
+ else
+ return 0;
+ }
+ else if (__builtin_strcmp (n, "log") == 0
+ || __builtin_strcmp (n, "log10") == 0)
+ e->retval = NAN;
+ else if (__builtin_strcmp (n, "pow") == 0)
+ {
+ if (e->arg1 < 0)
+ e->retval = NAN;
+ else if (e->arg1 == 0 && e->arg2 == 0)
+ e->retval = 1.0;
+ else if (e->arg1 == 0 && e->arg2 < 0)
+ {
+ double i;
+
+ if (modf (e->arg2, &i) == 0 && ((int64_t) i & 1) == 1)
+ e->retval = copysign (INFINITY, e->arg1);
+ else
+ e->retval = INFINITY;
+ }
+ else
+ return 0;
+ }
+ else if (__builtin_strcmp (n, "sqrt") == 0)
+ {
+ if (e->arg1 < 0)
+ e->retval = NAN;
+ else
+ return 0;
+ }
+ else
+ return 0;
+
+ return 1;
+}
+
+#endif
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