Fix test-fexcept when "inexact" implicitly raised.

ISO C allows feraiseexcept to raise "inexact", in addition to the
requested exceptions, when requested to raise "overflow" or
"underflow".  Testing on ARM and PowerPC e500 (where glibc's
feraiseexcept has this property) showed that the new test-fexcept test
failed to allow for this; this patch fixes it, by wrapping
feraiseexcept to clear FE_INEXACT if implicitly raised and not raised
before the call.  (It would also be possible to do this with
fesetexcept, which always affects exactly the requested flags, but
this patch avoids making this fix depend on the fesetexcept changes.)

Tested for x86_64, x86, arm and e500.

	* math/test-fexcept.c (feraiseexcept_exact): New function.
	(test_set): Call feraiseexcept_exact instead of feraiseexcept.
	(test_except): Likewise.

2 files changed, 37 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 15bd364777..58f4e1a32e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2016-08-12  Joseph Myers  <joseph@codesourcery.com>
+
+	* math/test-fexcept.c (feraiseexcept_exact): New function.
+	(test_set): Call feraiseexcept_exact instead of feraiseexcept.
+	(test_except): Likewise.
+
 2016-08-10  Joseph Myers  <joseph@codesourcery.com>
 
 	[BZ #20455]
diff --git a/math/test-fexcept.c b/math/test-fexcept.c
index 5e181a1f8c..36d14c548e 100644
--- a/math/test-fexcept.c
+++ b/math/test-fexcept.c
@@ -20,6 +20,35 @@
 #include <stdio.h>
 #include <math-tests.h>
 
+/* Like feraiseexcept, but raise exactly the specified exceptions EXC,
+   without possibly raising "inexact" together with "overflow" or
+   "underflow" as permitted by ISO C.  (This is not used with traps
+   enabled, so side-effects from raising and then clearing "inexact"
+   are irrelevant.)  */
+
+static int
+feraiseexcept_exact (int exc)
+{
+#ifdef FE_INEXACT
+  int mask = 0;
+#ifdef FE_OVERFLOW
+  mask |= FE_OVERFLOW;
+#endif
+#ifdef FE_UNDERFLOW
+  mask |= FE_UNDERFLOW;
+#endif
+  if ((exc & FE_INEXACT) != 0
+      || (exc & mask) == 0
+      || fetestexcept (FE_INEXACT) != 0)
+    return feraiseexcept (exc);
+  int ret = feraiseexcept (exc);
+  feclearexcept (FE_INEXACT);
+  return ret;
+#else
+  return feraiseexcept (exc);
+#endif
+}
+
 static int
 test_set (int initial, const fexcept_t *saved, int mask, int expected)
 {
@@ -28,7 +57,7 @@ test_set (int initial, const fexcept_t *saved, int mask, int expected)
   printf ("Testing set: initial exceptions %x, mask %x, expected %x\n",
 	  (unsigned int) initial, (unsigned int) mask,
 	  (unsigned int) expected);
-  int ret = feraiseexcept (initial);
+  int ret = feraiseexcept_exact (initial);
   if (ret != 0)
     {
       puts ("feraiseexcept failed");
@@ -81,7 +110,7 @@ test_except (int exc, const char *exc_name)
       return result;
     }
 
-  ret = feraiseexcept (exc);
+  ret = feraiseexcept_exact (exc);
   if (ret == 0)
     printf ("feraiseexcept (%s) succeeded\n", exc_name);
   else