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Re: [PATCH] specify large command line option arguments (PR 82063)


On 07/21/2018 06:42 PM, H.J. Lu wrote:
On Fri, Jul 20, 2018 at 1:57 PM, Martin Sebor <msebor@gmail.com> wrote:
On 07/19/2018 04:31 PM, Jeff Law wrote:

On 06/24/2018 03:05 PM, Martin Sebor wrote:

Storing integer command line option arguments in type int
limits options such as -Wlarger-than= or -Walloca-larger-than
to at most INT_MAX (see bug 71905).  Larger values wrap around
zero.  The value zero is considered to disable the option,
making it impossible to specify a zero limit.

To get around these limitations, the -Walloc-size-larger-than=
option accepts a string argument that it then parses itself
and interprets as HOST_WIDE_INT.  The option also accepts byte
size suffixes like KB, MB, GiB, etc. to make it convenient to
specify very large limits.

The int limitation is obviously less than ideal in a 64-bit
world.  The treatment of zero as a toggle is just a minor wart.
The special treatment to make it work for just a single option
makes option handling inconsistent.  It should be possible for
any option that takes an integer argument to use the same logic.

The attached patch enhances GCC option processing to do that.
It changes the storage type of option arguments from int to
HOST_WIDE_INT and extends the existing (although undocumented)
option property Host_Wide_Int to specify wide option arguments.
It also introduces the ByteSize property for options for which
specifying the byte-size suffix makes sense.

To make it possible to consider zero as a meaningful argument
value rather than a flag indicating that an option is disabled
the patch also adds a CLVC_SIZE enumerator to the cl_var_type
enumeration, and modifies how options of the kind are handled.

Warning options that take large byte-size arguments can be
disabled by specifying a value equal to or greater than
HOST_WIDE_INT_M1U.  For convenience, aliases in the form of
-Wno-xxx-larger-than have been provided for all the affected
options.

In the patch all the existing -larger-than options are set
to PTRDIFF_MAX.  This makes them effectively enabled, but
because the setting is exceedingly permissive, and because
some of the existing warnings are already set to the same
value and some other checks detect and reject such exceedingly
large values with errors, this change shouldn't noticeably
affect what constructs are diagnosed.

Although all the options are set to PTRDIFF_MAX, I think it
would make sense to consider setting some of them lower, say
to PTRDIFF_MAX / 2.  I'd like to propose that in a followup
patch.

To minimize observable changes the -Walloca-larger-than and
-Wvla-larger-than warnings required more extensive work to
make of the new mechanism because of the "unbounded" argument
handling (the warnings trigger for arguments that are not
visibly constrained), and because of the zero handling
(the warnings also trigger


Martin


gcc-82063.diff


PR middle-end/82063 - issues with arguments enabled by -Wall

gcc/ada/ChangeLog:

        PR middle-end/82063
        * gcc-interface/misc.c (gnat_handle_option): Change function
argument
        to HOST_WIDE_INT.

gcc/brig/ChangeLog:
        * brig/brig-lang.c (brig_langhook_handle_option): Change function
        argument to HOST_WIDE_INT.

gcc/c-family/ChangeLog:

        PR middle-end/82063
        * c-common.h (c_common_handle_option): Change function argument
        to HOST_WIDE_INT.
        * c-opts.c (c_common_init_options): Same.
        (c_common_handle_option): Same.  Remove special handling of
        OPT_Walloca_larger_than_ and OPT_Wvla_larger_than_.
        * c.opt (-Walloc-size-larger-than, -Walloca-larger-than): Change
        options to take a HOST_WIDE_INT argument and accept a byte-size
        suffix.  Initialize.
        (-Wvla-larger-than): Same.
        (-Wno-alloc-size-larger-than, -Wno-alloca-larger-than): New.
        (-Wno-vla-larger-than): Same.


gcc/fortran/ChangeLog:

        PR middle-end/82063
        * gfortran.h (gfc_handle_option): Change function argument
        to HOST_WIDE_INT.
        * options.c (gfc_handle_option): Same.

gcc/go/ChangeLog:

        PR middle-end/82063
        * go-lang.c (go_langhook_handle_option): Change function argument
        to HOST_WIDE_INT.

gcc/lto/ChangeLog:

        PR middle-end/82063
        * lto-lang.c (lto_handle_option): Change function argument
        to HOST_WIDE_INT.

gcc/testsuite/ChangeLog:

        PR middle-end/82063
        * gcc.dg/Walloc-size-larger-than-16.c: Adjust.
        * gcc.dg/Walloca-larger-than.c: New test.
        * gcc.dg/Wframe-larger-than-2.c: New test.
        * gcc.dg/Wlarger-than3.c: New test.
        * gcc.dg/Wvla-larger-than-3.c: New test.

gcc/ChangeLog:

        PR middle-end/82063
        * builtins.c (expand_builtin_alloca): Adjust.
        * calls.c (alloc_max_size): Simplify.
        * cgraphunit.c (cgraph_node::expand): Adjust.
        * common.opt (larger_than_size, warn_frame_larger_than): Remove
        variables.
        (frame_larger_than_size): Same.
        (-Wframe-larger-than, -Wlarger-than, -Wstack-usage): Change
options
        to take a HOST_WIDE_INT argument and accept a byte-size suffix.
        Initialize.
        * doc/invoke.texi (GCC Command Options): Document option
arguments.
        Explain byte-size arguments and suffixes.
        (-Wvla-larger-than, -Wno-alloc-size-larger-than): Update.
        (-Wno-alloca-larger-than, -Wno-vla-larger-than): Same.
        (-Wframe-larger-than, -Wlarger-than, -Wstack-usage): Same.
        * doc/options.texi (UInteger): Expand.
        (Host_Wide_Int, ByteSize): Document new properties.
        * final.c (final_start_function_1): Include sizes in an error
message.
        * function.c (frame_offset_overflow): Same.
        * gimple-ssa-warn-alloca.c (pass_walloca::gate): Adjust.
        (alloca_call_type_by_arg): Change function argument to
HOST_WIDE_INT.
        Diagnose unbounded alloca calls only for limits of less than
        PTRDIFF_MAX.
        (alloca_call_type): Adjust.  Diagnose possibly out-of-bounds
alloca
        calls and VLA size only for limits of less than PTRDIFF_MAX.
Same
        for alloca(0).
        (pass_walloca::execute): Adjust.  Diagnose alloca calls in loops
        only for limits of less than PTRDIFF_MAX.
        * langhooks-def.h (lhd_handle_option): Change function argument
        to HOST_WIDE_INT.
        * langhooks.c (lhd_handle_option): Same.
        * langhooks.h (handle_option): Same.
        * opt-functions.awk (switch_bit_fields): Handle Host_Wide_Int and
        ByteSize flags.
        (var_type, var_type_struct): Same.
        (var_set): Handle ByteSize flag.
        * optc-gen.awk: Add comments to output to ease debugging.  Make
        use of HOST_WIDE_INT where appropriate.
        * opts-gen-save.awk:  Use %lx to format unsigned long.
        * opth-gen.awk: Change function argument to HOST_WIDE_INT.
        * opts-common.c (integral_argument): Return HOST_WIDE_INT and add
        arguments.  Parse bytes-size suffixes.
        (enum_arg_to_value): Change function argument to HOST_WIDE_INT.
        (enum_value_to_arg): Same.
        (decode_cmdline_option): Handle cl_host_wide_int.  Adjust.
        (handle_option): Adjust.
        (generate_option): Change function argument to HOST_WIDE_INT.
        (cmdline_handle_error): Adjust.
        (read_cmdline_option): Change function argument to HOST_WIDE_INT.
        (set_option): Change function argument to HOST_WIDE_INT.
        (option_enabled): Handle cl_host_wide_int.
        (get_option_state): Handle CLVC_SIZE.
        (control_warning_option): Same.
        * opts.c (common_handle_option): Change function argument to
        HOST_WIDE_INT.  Remove handling of OPT_Walloca_larger_than_ and
        OPT_Wvla_larger_than_.
        * opts.h (enum cl_var_type): Add an enumerator.
        * stor-layout.c (layout_decl): Print a more meaningful warning.
        * toplev.c (output_stack_usage): Adjust.

In the doc changes you refer to the -falign-* options.  All that stuff
recently changed.  Please make sure your references are still sane given
those recent changes.


As far as I can tell they're still valid.


+  /* When MAX_SIZE is greater than or equal to PTRDIFF_MAX treat
+     allocations that aren't visibly constrained as OK, otherwise
+     report them as (potentially) unbonded.  */

s/unbonded/unbounded/


Fixed.


OK with the nit fixed.  IF you need to update the doc changes as a
result of the -faligned-* changes, those are pre-approved.


I had to adjust a few more tests and make a couple of minor
tweaks as I noticed a coupled of test failures that I had
previously missed but the result was didn't show any more
regressions on x86_64.

Committed in r262910.


This caused:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86624

This may impact all 32-bit hosts.

r262923 should have fixed it.

Martin


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