[Bug math/17885] New: powerpc: fesetexceptflag not correct setting the new flag

["azanella at linux dot vnet.ibm.com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=17885

            Bug ID: 17885
           Summary: powerpc: fesetexceptflag not correct setting the new
                    flag
           Product: glibc
           Version: 2.20
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
          Assignee: unassigned at sourceware dot org
          Reporter: azanella at linux dot vnet.ibm.com

The following testcase:

#include <stdio.h>
#include <fenv.h>

void
show_fe_exceptions (void)
{
  printf ("current exceptions raised: ");
  if (fetestexcept (FE_DIVBYZERO))
    printf (" FE_DIVBYZERO");
  if (fetestexcept (FE_INEXACT))
    printf (" FE_INEXACT");
  if (fetestexcept (FE_INVALID))
    printf (" FE_INVALID");
  if (fetestexcept (FE_OVERFLOW))
    printf (" FE_OVERFLOW");
  if (fetestexcept (FE_UNDERFLOW))
    printf (" FE_UNDERFLOW");
  if (fetestexcept (FE_ALL_EXCEPT) == 0)
    printf (" none");
  printf ("\n");
}

int
main (void)
{
  fexcept_t excepts;

  /* Setup a "current" set of exception flags. */
  feraiseexcept (FE_INVALID);
  show_fe_exceptions ();

  /* Save current exception flags. */
  fegetexceptflag (&excepts, FE_ALL_EXCEPT);

  /* Temporarily raise two other exceptions. */
  feclearexcept (FE_ALL_EXCEPT);
  feraiseexcept (FE_OVERFLOW | FE_INEXACT);
  show_fe_exceptions ();

  /* Restore previous exception flags. */
  fesetexceptflag (&excepts, FE_ALL_EXCEPT);
  show_fe_exceptions ();

  return 0;
}


Fails on powerpc{32,64}-fpu:

$ gcc test.c -o test -lm
$ ./testrun.sh ./test
current exceptions raised:  FE_INVALID
current exceptions raised:  FE_INEXACT FE_OVERFLOW
current exceptions raised:  FE_INEXACT FE_INVALID FE_OVERFLOW

The expected result is:

$ ./test
current exceptions raised:  FE_INVALID
current exceptions raised:  FE_INEXACT FE_OVERFLOW
current exceptions raised:  FE_INVALID

This is due a typo in commit 18f2945ae9216cfcd53a162080a73e3d719de9e6, which
sets the new flag using the old value. The trivial patch fixes it:

diff --git a/sysdeps/powerpc/fpu/fsetexcptflg.c
b/sysdeps/powerpc/fpu/fsetexcptflg.c
index 5d99bf2..836d839 100644
--- a/sysdeps/powerpc/fpu/fsetexcptflg.c
+++ b/sysdeps/powerpc/fpu/fsetexcptflg.c
@@ -40,7 +40,7 @@ __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 (u.fenv);
+    fesetenv_register (n.fenv);

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

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