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powerpc: Do not raise exception traps for fesetexcept/fesetexceptflag (BZ 30988)

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According to ISO C23 (7.6.4.4), fesetexcept is supposed to set
floating-point exception flags without raising a trap (unlike
feraiseexcept, which is supposed to raise a trap if feenableexcept was
called with the appropriate argument).

This is a side-effect of how we implement the GNU extension
feenableexcept, where feenableexcept/fesetenv/fesetmode/feupdateenv
might issue prctl (PR_SET_FPEXC, PR_FP_EXC_PRECISE) depending of the
argument.  And on PR_FP_EXC_PRECISE, setting a floating-point exception
flag triggers a trap.

To make the both functions follow the C23, fesetexcept and
fesetexceptflag now fail if the argument may trigger a trap.

The math tests now check for an value different than 0, instead
of bail out as unsupported for EXCEPTION_SET_FORCES_TRAP.

Checked on powerpc64le-linux-gnu.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Adhemerval Zanella 2023-10-24 08:37:14 -03:00
parent f94446c38f
commit ecb1e7220d
4 changed files with 38 additions and 16 deletions
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24
math/test-fesetexcept-traps.c
View File

@ -39,16 +39,24 @@ 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);
_Static_assert (!(EXCEPTION_SET_FORCES_TRAP && !EXCEPTION_TESTS(float)),
"EXCEPTION_SET_FORCES_TRAP only makes sense if the "
"architecture suports exceptions");
if (ret == 0)
puts ("fesetexcept (FE_ALL_EXCEPT) succeeded");
else
{
if (EXCEPTION_SET_FORCES_TRAP)
{
puts ("unexpected fesetexcept success");
result = 1;
}
}
else if (!EXCEPTION_SET_FORCES_TRAP)
{
puts ("fesetexcept (FE_ALL_EXCEPT) failed");
if (EXCEPTION_TESTS (float))

16
math/test-fexcept-traps.c
View File

@ -63,14 +63,16 @@ 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)
_Static_assert (!(EXCEPTION_SET_FORCES_TRAP && !EXCEPTION_TESTS(float)),
"EXCEPTION_SET_FORCES_TRAP only makes sense if the "
"architecture suports exceptions");
if (ret != 0 && !EXCEPTION_SET_FORCES_TRAP)
{
puts ("fesetexceptflag failed");
result = 1;

5
sysdeps/powerpc/fpu/fesetexcept.c
View File

@ -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. */

9
sysdeps/powerpc/fpu/fsetexcptflg.c
View File

@ -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)