math: fix exp10 not to raise invalid exception on NaN

This was not caught earlier because gcc incorrectly generates quiet
relational operators that never raise exceptions.

src/math/exp10.c

@@ -1,5 +1,6 @@
 #define _GNU_SOURCE
 #include <math.h>
+#include <stdint.h>
 #include "libc.h"
 
 double exp10(double x)
@@ -11,7 +12,9 @@ double exp10(double x)
 		1e10, 1e11, 1e12, 1e13, 1e14, 1e15
 	};
 	double n, y = modf(x, &n);
-	if (fabs(n) < 16) {
+	union {double f; uint64_t i;} u = {n};
+	/* fabs(n) < 16 without raising invalid on nan */
+	if ((u.i>>52 & 0x7ff) < 0x3ff+4) {
 		if (!y) return p10[(int)n+15];
 		y = exp2(3.32192809488736234787031942948939 * y);
 		return y * p10[(int)n+15];

src/math/exp10f.c

@@ -1,5 +1,6 @@
 #define _GNU_SOURCE
 #include <math.h>
+#include <stdint.h>
 #include "libc.h"
 
 float exp10f(float x)
@@ -9,7 +10,9 @@ float exp10f(float x)
 		1, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7
 	};
 	float n, y = modff(x, &n);
-	if (fabsf(n) < 8) {
+	union {float f; uint32_t i;} u = {n};
+	/* fabsf(n) < 8 without raising invalid on nan */
+	if ((u.i>>23 & 0xff) < 0x7f+3) {
 		if (!y) return p10[(int)n+7];
 		y = exp2f(3.32192809488736234787031942948939f * y);
 		return y * p10[(int)n+7];

src/math/exp10l.c

@@ -2,13 +2,14 @@
 #include <float.h>
 #include <math.h>
 #include "libc.h"
+#include "libm.h"
 
 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
 long double exp10l(long double x)
 {
 	return exp10(x);
 }
-#else
+#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
 long double exp10l(long double x)
 {
 	static const long double p10[] = {
@@ -18,7 +19,9 @@ long double exp10l(long double x)
 		1e10, 1e11, 1e12, 1e13, 1e14, 1e15
 	};
 	long double n, y = modfl(x, &n);
-	if (fabsl(n) < 16) {
+	union ldshape u = {n};
+	/* fabsl(n) < 16 without raising invalid on nan */
+	if ((u.i.se & 0x7fff) < 0x3fff+4) {
 		if (!y) return p10[(int)n+15];
 		y = exp2l(3.32192809488736234787031942948939L * y);
 		return y * p10[(int)n+15];