Make fallback fesetexceptflag always succeed (bug 21028).

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.

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

3 files changed, 17 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index c67476fca5..172b0c9275 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+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.
+
 2017-01-05  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
 	[BZ #20558]
diff --git a/math/fsetexcptflg.c b/math/fsetexcptflg.c
index 2e8237ee32..e79095b04e 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 6aa54b49b4..854080173a 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);