Re: [PATCH 5/7] riscv: Fix feenvupdate with FE_DFL_ENV (BZ 31022)

[Szabolcs Nagy <szabolcs.nagy@arm.com>]

The 11/03/2023 09:24, Adhemerval Zanella wrote:
> libc_feupdateenv_riscv should check for FE_DFL_ENV, similar to
> libc_fesetenv_riscv.
> 
> Also extend the test-fenv.c to test fenvupdate.
> 
> Checked on riscv under qemu-system.

the test fails on aarch64 when trapping is supported.

> +++ b/math/test-fenv.c
> @@ -196,6 +196,30 @@ set_single_exc (const char *test_name, int fe_exc, fexcept_t exception)
>    feclearexcept (exception);
>    test_exceptions (str, ALL_EXC ^ fe_exc, 0);
>  }
> +
> +static void
> +update_single_exc (const char *test_name, const fenv_t *envp, int fe_exc,
> +		   int fe_exc_clear, fexcept_t exception)
> +{
> +  char str[200];
> +  /* The standard allows the inexact exception to be set together with the
> +     underflow and overflow exceptions.  So ignore the inexact flag if the
> +     others are raised.  */
> +  int ignore_inexact = (fe_exc & (UNDERFLOW_EXC | OVERFLOW_EXC)) != 0;
> +
> +  strcpy (str, test_name);
> +  strcat (str, ": set flag, with rest not set");
> +  feclearexcept (FE_ALL_EXCEPT);
> +  feraiseexcept (exception);

this relies on disabled trapping.

> +  feupdateenv (envp);
> +  test_exceptions (str, fe_exc, ignore_inexact);
> +
> +  strcpy (str, test_name);
> +  strcat (str, ": clear flag, rest also unset");
> +  feclearexcept (exception);
> +  feupdateenv (envp);
> +  test_exceptions (str, fe_exc_clear, ignore_inexact);
> +}
...
>  /* Test that program aborts with no masked interrupts */
>  static void
> -feenv_nomask_test (const char *flag_name, int fe_exc)
> +feenv_nomask_test (const char *flag_name, int fe_exc, int (*func)(const fenv_t *))
>  {
>  # if defined FE_NOMASK_ENV
>    int status;
>    pid_t pid;
>  
>    if (!EXCEPTION_ENABLE_SUPPORTED (FE_ALL_EXCEPT)
> -      && fesetenv (FE_NOMASK_ENV) != 0)
> +      && func (FE_NOMASK_ENV) != 0)

trapping is enabled here on targets where trapping is optional.

> +static void
> +feupdate_single_test (const char *flag_name, int fe_exc)
> +{
> +  feenv_nomask_test (flag_name, fe_exc, feupdateenv);
> +  feenv_mask_test (flag_name, fe_exc, feupdateenv);
> +}

trapping is still on after this function.

> +static void
> +feupdateenv_single_test (const char *test_name, int fe_exc,
> +			 fexcept_t exception)
> +{
> +  char str[100];
> +  fenv_t env;
> +  int res;
> +
> +  snprintf (str, sizeof str, "feupdateenv %s and FL_DFL_ENV", test_name);
> +  update_single_exc (str, FE_DFL_ENV, fe_exc, NO_EXC, exception);

this relies on disabled trapping.

> +static void
> +feupdateenv_tests (void)
> +{
...
> +#ifdef FE_OVERFLOW
> +  feupdate_single_test ("FE_OVERFLOW", FE_OVERFLOW);
> +#endif
> +
> +#ifdef FE_DIVBYZERO
> +  feupdateenv_single_test ("DIVBYZERO", DIVBYZERO_EXC, FE_DIVBYZERO);
> +#endif

this test fails because previous enables trapping mode.

fwiw a feupdateenv (FE_DFL_ENV); in between the tests
makes math/test-fenv pass.