[Bug math/30988] fesetexcept raises floating-point exception traps on ppc, ppc64, ppc64le

["adhemerval.zanella at linaro dot org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=30988

--- Comment #4 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> ---
In fact, we are already aware of this limitation and the tests are masking off
this issue with the internal EXCEPTION_SET_FORCES_TRAP flag (set only for
powerpc). I am unsure why Joseph did not consider this a bug when he added the
tests. The fesetexceptflag has the same issue, so I think we will need
something like:

diff --git a/math/test-fesetexcept-traps.c b/math/test-fesetexcept-traps.c
index 71b6e45b33..96f6c4752f 100644
--- a/math/test-fesetexcept-traps.c
+++ b/math/test-fesetexcept-traps.c
@@ -39,16 +39,13 @@ do_test (void)
       return result;
     }

-  if (EXCEPTION_SET_FORCES_TRAP)
-    {
-      puts ("setting exceptions traps, cannot test on this architecture");
-      return 77;
-    }
-  /* Verify fesetexcept does not cause exception traps.  */
+  /* Verify fesetexcept does not cause exception traps.  For architectures
+     where setting the exception might result in traps the function should
+     return a nonzero value.  */
   ret = fesetexcept (FE_ALL_EXCEPT);
   if (ret == 0)
     puts ("fesetexcept (FE_ALL_EXCEPT) succeeded");
-  else
+  else if (!EXCEPTION_SET_FORCES_TRAP)
     {
       puts ("fesetexcept (FE_ALL_EXCEPT) failed");
       if (EXCEPTION_TESTS (float))
diff --git a/math/test-fexcept-traps.c b/math/test-fexcept-traps.c
index 9701c3c320..9b8f583ae6 100644
--- a/math/test-fexcept-traps.c
+++ b/math/test-fexcept-traps.c
@@ -63,14 +63,11 @@ do_test (void)
       result = 1;
     }

-  if (EXCEPTION_SET_FORCES_TRAP)
-    {
-      puts ("setting exceptions traps, cannot test on this architecture");
-      return 77;
-    }
-  /* The test is that this does not cause exception traps.  */
+  /* The test is that this does not cause exception traps.  For architectures
+     where setting the exception might result in traps the function should
+     return a nonzero value.  */
   ret = fesetexceptflag (&saved, FE_ALL_EXCEPT);
-  if (ret != 0)
+  if (ret != 0 && !EXCEPTION_SET_FORCES_TRAP)
     {
       puts ("fesetexceptflag failed");
       result = 1;
diff --git a/sysdeps/powerpc/fpu/fesetexcept.c
b/sysdeps/powerpc/fpu/fesetexcept.c
index 609a148a95..2850156d3a 100644
--- a/sysdeps/powerpc/fpu/fesetexcept.c
+++ b/sysdeps/powerpc/fpu/fesetexcept.c
@@ -31,6 +31,11 @@ fesetexcept (int excepts)
            & FE_INVALID_SOFTWARE));
   if (n.l != u.l)
     {
+      if (n.l & fenv_exceptions_to_reg (excepts))
+       /* Setting the exception flags may trigger a trap.  ISO C 23 § 7.6.4.4
+           does not allow it.   */
+       return -1;
+
       fesetenv_register (n.fenv);

       /* Deal with FE_INVALID_SOFTWARE not being implemented on some chips. 
*/
diff --git a/sysdeps/powerpc/fpu/fsetexcptflg.c
b/sysdeps/powerpc/fpu/fsetexcptflg.c
index 2b22f913c0..6517e8ea03 100644
--- a/sysdeps/powerpc/fpu/fsetexcptflg.c
+++ b/sysdeps/powerpc/fpu/fsetexcptflg.c
@@ -44,7 +44,14 @@ __fesetexceptflag (const fexcept_t *flagp, int excepts)
      This may cause floating-point exceptions if the restored state
      requests it.  */
   if (n.l != u.l)
-    fesetenv_register (n.fenv);
+    {
+      if (n.l & fenv_exceptions_to_reg (excepts))
+       /* Setting the exception flags may trigger a trap.  ISO C 23 § 7.6.4.4
+           does not allow it.   */
+       return -1;
+
+      fesetenv_register (n.fenv);
+    }

   /* Deal with FE_INVALID_SOFTWARE not being implemented on some chips.  */
   if (flag & FE_INVALID)

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