Make fallback fesetexceptflag always succeed (bug 21028) [committed]

[Joseph Myers <joseph at codesourcery dot com>]

The fallback implementation of fesetexceptflag currently fails if any
exceptions are specified.  It should always succeed, because the
exception state is always that all exceptions (if any are defined in
<fenv.h> but not supported in this configuration) are always clear,
just as fallback fetestexcept always succeeds and fallback fesetenv
always succeeds unless asked to set FE_NOMASK_ENV.

This patch fixes it accordingly.  Together with the patch to
test-fexcept.c to allow feraiseexcept to fail in another place, this
stops that test from failing for MIPS soft-float.

Tested for mips64 soft-float.  Committed.

2017-01-05  Joseph Myers  <joseph@codesourcery.com>

	[BZ #21028]
	* math/fsetexcptflg.c (__fesetexceptflag): Always return 0.
	* math/test-fexcept.c (test_set): Allow failure of feraiseexcept
	if EXCEPTION_TESTS returns false.

diff --git a/math/fsetexcptflg.c b/math/fsetexcptflg.c
index 2e8237e..e79095b 100644
--- a/math/fsetexcptflg.c
+++ b/math/fsetexcptflg.c
@@ -23,8 +23,9 @@
 int
 __fesetexceptflag (const fexcept_t *flagp, int excepts)
 {
-  /* This always fails unless nothing needs to be done.  */
-  return (excepts != 0);
+  /* This always succeeds, as all exceptions are always clear
+     (including in the saved state) so nothing needs to be done.  */
+  return 0;
 }
 #if SHLIB_COMPAT (libm, GLIBC_2_1, GLIBC_2_2)
 strong_alias (__fesetexceptflag, __old_fesetexceptflag)
diff --git a/math/test-fexcept.c b/math/test-fexcept.c
index 6aa54b4..8540801 100644
--- a/math/test-fexcept.c
+++ b/math/test-fexcept.c
@@ -61,7 +61,13 @@ test_set (int initial, const fexcept_t *saved, int mask, int expected)
   if (ret != 0)
     {
       puts ("feraiseexcept failed");
-      result = 1;
+      if (initial == 0 || EXCEPTION_TESTS (float))
+	{
+	  puts ("failure of feraiseexcept was unexpected");
+	  result = 1;
+	}
+      else
+	puts ("failure of feraiseexcept OK, skipping further tests");
       return result;
     }
   ret = fesetexceptflag (saved, mask);

-- 
Joseph S. Myers
joseph@codesourcery.com