Fix scalb spurious "invalid" exceptions (bug 16770).

This patch fixes bug 16770, spurious "invalid" exceptions from scalb
when testing whether the second argument is an integer, by inserting
appropriate range checks to determine whether a cast to int is safe.
(Note that invalid_fn is a function that handles both nonintegers and
large integers, distinguishing them reliably using functions such as
__rint; note also that there are no issues with scalb needing to avoid
spurious "inexact" exceptions - it's an old-POSIX XSI function, not a
standard C function bound to an IEEE 754 operation - although the
return value is still fully determined.)

Tested x86_64 and x86.

	[BZ #16770]
	* math/e_scalb.c (__ieee754_scalb): Check second argument is not
	too large before casting to int.
	* math/e_scalbf.c (__ieee754_scalbf): Likewise.
	* math/e_scalbl.c (__ieee754_scalbl): Likewise.
	* math/libm-test.inc (scalb_test_data): Add more tests.

4 files changed, 20 insertions, 3 deletions

diff --git a/math/e_scalb.c b/math/e_scalb.c
index bddedfa032..146d49e1c3 100644
--- a/math/e_scalb.c
+++ b/math/e_scalb.c
@@ -50,7 +50,7 @@ __ieee754_scalb (double x, double fn)
 	return x;
       return x / -fn;
     }
-  if (__glibc_unlikely ((double) (int) fn != fn))
+  if (__glibc_unlikely (fabs (fn) >= 0x1p31 || (double) (int) fn != fn))
     return invalid_fn (x, fn);
 
   return __scalbn (x, (int) fn);
diff --git a/math/e_scalbf.c b/math/e_scalbf.c
index 319752c993..3f2e853353 100644
--- a/math/e_scalbf.c
+++ b/math/e_scalbf.c
@@ -50,7 +50,7 @@ __ieee754_scalbf (float x, float fn)
 	return x;
       return x / -fn;
     }
-  if (__glibc_unlikely ((float) (int) fn != fn))
+  if (__glibc_unlikely (fabsf (fn) >= 0x1p31f || (float) (int) fn != fn))
     return invalid_fn (x, fn);
 
   return __scalbnf (x, (int) fn);
diff --git a/math/e_scalbl.c b/math/e_scalbl.c
index 5815a0d67b..739db7a188 100644
--- a/math/e_scalbl.c
+++ b/math/e_scalbl.c
@@ -50,7 +50,7 @@ __ieee754_scalbl (long double x, long double fn)
 	return x;
       return x / -fn;
     }
-  if (__glibc_unlikely ((long double) (int) fn != fn))
+  if (__glibc_unlikely (fabsl (fn) >= 0x1p31L || (long double) (int) fn != fn))
     return invalid_fn (x, fn);
 
   return __scalbnl (x, (int) fn);
diff --git a/math/libm-test.inc b/math/libm-test.inc
index cefcb9682a..0eff34a0ca 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -9134,6 +9134,23 @@ static const struct test_ff_f_data scalb_test_data[] =
     TEST_ff_f (scalb, plus_infty, qnan_value, qnan_value, NO_INEXACT_EXCEPTION),
     TEST_ff_f (scalb, qnan_value, qnan_value, qnan_value, NO_INEXACT_EXCEPTION),
 
+    TEST_ff_f (scalb, max_value, max_value, plus_oflow, OVERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, max_value, -max_value, plus_uflow, UNDERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, 1, max_value, plus_oflow, OVERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, 1, -max_value, plus_uflow, UNDERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, min_value, max_value, plus_oflow, OVERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, min_value, -max_value, plus_uflow, UNDERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, min_subnorm_value, max_value, plus_oflow, OVERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, min_subnorm_value, -max_value, plus_uflow, UNDERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, -max_value, max_value, minus_oflow, OVERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, -max_value, -max_value, minus_uflow, UNDERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, -1, max_value, minus_oflow, OVERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, -1, -max_value, minus_uflow, UNDERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, -min_value, max_value, minus_oflow, OVERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, -min_value, -max_value, minus_uflow, UNDERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, -min_subnorm_value, max_value, minus_oflow, OVERFLOW_EXCEPTION),
+    TEST_ff_f (scalb, -min_subnorm_value, -max_value, minus_uflow, UNDERFLOW_EXCEPTION),
+
     TEST_ff_f (scalb, 0.8L, 4, 12.8L),
     TEST_ff_f (scalb, -0.854375L, 5, -27.34L),
   };