[PATCH] Fix --help -Q output

[Richard Biener]

On Mon, Nov 29, 2021 at 4:16 PM Martin Liška <mliska@suse.cz> wrote:
>
> There are cases where a default option value is -1 and
> auto-detection happens in e.g. target.
>
> Do not print these options. Leads to the following diff:
>
> -  -fdelete-null-pointer-checks                 [enabled]
> +  -fdelete-null-pointer-checks
> @@ -332 +332 @@
> -  -fleading-underscore                 [enabled]
> +  -fleading-underscore
> @@ -393 +393 @@
> -  -fprefetch-loop-arrays               [enabled]
> +  -fprefetch-loop-arrays
> @@ -502 +502 @@
> -  -fstrict-volatile-bitfields          [enabled]
> +  -fstrict-volatile-bitfields
> @@ -533 +533 @@
> -  -ftree-loop-if-convert               [enabled]
> +  -ftree-loop-if-convert
>
> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
>
> Ready to be installed?
> Thanks,
> Martin
>
>         PR middle-end/103438
>
> gcc/ChangeLog:
>
>         * opts-common.c (option_enabled): Return flag_var for BOOLEAN
>         types (the can contain an unknown value -1).
> ---
>   gcc/opts-common.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/gcc/opts-common.c b/gcc/opts-common.c
> index 9d1914ff2ff..c4a19b9a0b6 100644
> --- a/gcc/opts-common.c
> +++ b/gcc/opts-common.c
> @@ -1586,7 +1586,8 @@ option_flag_var (int opt_index, struct gcc_options *opts)
>   }
>
>   /* Return 1 if option OPT_IDX is enabled in OPTS, 0 if it is disabled,
> -   or -1 if it isn't a simple on-off switch.  */
> +   or -1 if it isn't a simple on-off switch (or if the value is unknown,
> +   typically set later in target).  */
>
>   int
>   option_enabled (int opt_idx, unsigned lang_mask, void *opts)
> @@ -1608,9 +1609,9 @@ option_enabled (int opt_idx, unsigned lang_mask, void *opts)
>         {
>         case CLVC_BOOLEAN:
>         if (option->cl_host_wide_int)
> -         return *(HOST_WIDE_INT *) flag_var != 0;
> +         return *(HOST_WIDE_INT *) flag_var;
>         else
> -         return *(int *) flag_var != 0;
> +         return *(int *) flag_var;

So can we assert that only 1, 0 and -1 are returned here?  For example I see
(random picked)

 /* [64] = */ {
    "--param=align-threshold=",
    "Select fraction of the maximal frequency of executions of basic
block in function given basic block get alignment.",
    NULL,
    NULL,
    NULL, NULL, N_OPTS, N_OPTS, 23, /* .neg_idx = */ -1,
    CL_COMMON | CL_JOINED | CL_OPTIMIZATION | CL_PARAMS,
    0, 0, 0, 0, 0, 0, 0, 0, 1 /* UInteger */, 0, 0, 0,
    offsetof (struct gcc_options, x_param_align_threshold), 0,
CLVC_BOOLEAN, 0, 1, 65536 },

or

 /* [877] = */ {
    "-faligned-new=",
    "-faligned-new=<N>  Use C++17 over-aligned type allocation for
alignments greater than N.",
    NULL,
    NULL,
    NULL, NULL, N_OPTS, N_OPTS, 13, /* .neg_idx = */ -1,
    CL_CXX | CL_ObjCXX | CL_JOINED,
    0, 0, 0, 0, 0, 0, 1 /* RejectNegative */, 0, 1 /* UInteger */, 0, 0, 0,
    offsetof (struct gcc_options, x_aligned_new_threshold), 0,
CLVC_BOOLEAN, 0, -1, -1 },

and the "docs" say

  /* The switch is enabled when FLAG_VAR is nonzero.  */
  CLVC_BOOLEAN,

so a -1 init contradicts this.  I also wonder what determines the
CLVC_* kind, it seems
it's simply the "default" kind chosen when nothing else matches in var_set().

>
>         case CLVC_EQUAL:
>         if (option->cl_host_wide_int)
> --
> 2.34.0
>