math: fix pow(+-0,-inf) not to raise divbyzero flag

this reverts the commit f29fea00b5bc72d4b8abccba2bb1e312684d1fce
which was based on a bug in C99 and POSIX and did not match IEEE-754
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1515.pdf

diff --git a/src/math/pow.c b/src/math/pow.c
index 82f684bdb0e363c6846d0f7dde445cf4b5818618..b66f632d8eea9fce118c087677c755f391c6df85 100644 (file)
--- a/src/math/pow.c
+++ b/src/math/pow.c
@@ -143,7 +143,7 @@ double pow(double x, double y)
                                return 1.0;
                        else if (ix >= 0x3ff00000) /* (|x|>1)**+-inf = inf,0 */
                                return hy >= 0 ? y : 0.0;
-                       else if ((ix|lx) != 0)     /* (|x|<1)**+-inf = 0,inf if x!=0 */
+                       else                       /* (|x|<1)**+-inf = 0,inf */
                                return hy >= 0 ? 0.0 : -y;
                }
                if (iy == 0x3ff00000) {    /* y is +-1 */

diff --git a/src/math/powf.c b/src/math/powf.c
index 59baf6f3809cf0b9dfa9d6d55442c86a41e058fd..427c8965b9e8e78bca69660427a4e313087c3e0a 100644 (file)
--- a/src/math/powf.c
+++ b/src/math/powf.c
@@ -90,7 +90,7 @@ float powf(float x, float y)
                        return 1.0f;
                else if (ix > 0x3f800000)  /* (|x|>1)**+-inf = inf,0 */
                        return hy >= 0 ? y : 0.0f;
-               else if (ix != 0)          /* (|x|<1)**+-inf = 0,inf if x!=0 */
+               else                       /* (|x|<1)**+-inf = 0,inf */
                        return hy >= 0 ? 0.0f: -y;
        }
        if (iy == 0x3f800000)    /* y is +-1 */

diff --git a/src/math/powl.c b/src/math/powl.c
index a765706d9b34c4121a5d62750f158681ce39be58..5b6da07b2efcce53795ec80da4a787208a2cb733 100644 (file)
--- a/src/math/powl.c
+++ b/src/math/powl.c
@@ -227,7 +227,7 @@ long double powl(long double x, long double y)
        if (y <= -LDBL_MAX) {
                if (x > 1.0 || x < -1.0)
                        return 0.0;
-               if (x != 0.0)
+               if (x != 0.0 || y == -INFINITY)
                        return INFINITY;
        }
        if (x >= LDBL_MAX) {