[Bug other/82063] New: issues with arguments enabled by -Wall

["wilson at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82063

            Bug ID: 82063
           Summary: issues with arguments enabled by -Wall
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: wilson at gcc dot gnu.org
  Target Milestone: ---

Noticed this while looking at the -Wall documentation.

-Walloc-alloc-size-larger-than= is listed in the c-family/c.opt file as being
enabled by -Wall, however, nothing is provided for the enable/disable values,
as is done for every other -Wall enabled options that takes an argument.  The
code tries to enable it using the default value of 1 and a NULL string, but
since the option takes a string argument, the 1 value is ignored, and the NULL
string is used, so it gets set to zero, which disables it.  I stepped through
cc1 code in the debugger to verify this.  If we really do want this enabled by
-Wall, then we probably need an extension to LangEnabledBy to specify on/off
strings for arguments that take strings.

Both -Warray-bounds and -Warray-bounds= are listed in the c.opt file as being
enabled by -Wall, but they are the same option, and it causes this one option
to be processed twice in the C_handle_option_auto function in the generated
options.c file.  It gets set to the same value twice, so it does work as
intended, but this is wasteful.